GIFT OF THE COMPLETE Practical Machinist : EMBRACING LATHE WORK, VISE WORK, DRILLS AND DRILLING, TAPS AND DIES, HARDENING AND TEMPERING, THE MAKING AND USE OF TOOLS, TOOL GRINDING, MARKING OUT ORK, ETC. BY JOSHUA ROSE Illustrate!* ifi 8Hjm $un&n& anJr F( FIFTE $$7 V ' FDITIOA^ - \ THOROUGHLY REUSED ANDJft CRE^T.PART REWRITTEN. PHILADELPHIA . HENRY CAREY BAIRD & CO., INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 WALNUT STREET. LONDON: SAMPSON LOW, MARSTON, SEARLE & RIVINGTON, CROWN BUILDINGS, 188 FI.KKT STIIKET. 1887. Copyright, JOSHUA ROSE, 1885. COLLINS, I'KINT-KR PREFACE TO THE THIRTEENTH EDITION. IN presenting to machinists a thoroughly revised edition of this book, the author would be ungrateful did he omit to express his sincere thanks for the unusual welcome which it has met at the hands of American machinists, and also for the large number of kindly letters of appreciation from the many, on both sides of the Atlantic, with whom he has become acquainted through the medium of it. This revision brings the work thoroughly up to date, while maintaining its chief characteristic of being as intelligible to the student and apprentice as it is to the skilful machinist. JOSHUA ROSE. NEW YORK CITY, January 1, 1885. P. O. Box 3306. (13) 251004 CONTENTS. CHAPTER I. CUTTING TOOLS FOR LATHES AND PLANING MACHINES. Importance of the Lathe ; Steel of which Cutting Tools for Lathes, Planing Machines, etc., are made ; Classification of Lathe-cutting Tools 25 Classification of Slide-rest Tools ; The Forming of Cutting Tools ; Illustration of the manner in which a Lathe Tool cuts the Metal ; Principal considera- tion in determining the proper shape of a Cutting Tool 26 Strain upon a Tool 29 Hake in Tools 3ft Principles determining the proper form of the cutting edge of a Tool 33 Bound-Nosed Tools 36 Square-Nosed Tools 37 Angles at which Tools become Cutters or Scrapers respectively 39 Effect of the diameter of the work and the rate of tool feed on the amount of clearance by the bottoir rake or side rake of a Tool ; Bearing of the height of the cutting edge of a Tool, with relation to the work, on its cutting qualities 40 Practice of Sir Joseph Whitworth ; Positions in which all Tools should be held 41 Cutting off Parting or Grooving Tools 44 (15) 16 CONTENTS. Side Tools for Iron 47 Front Tool- for Brass Work 50 Side Tool for Brass Work 53 Special Forms of Lathe Tools 54 Tool Holders 55 Woodbridge's patent Tools and Tool Holder 57 CHAPTER II. CUTTING SPEED AND FEED. Meaning of the terms " Cutting Speed " and " Feed " , Planing Machines ; Great importance of " Feed " and " Speed in Lathe Work 64 44 Feed " and " Speed " for various kinds of work 65 Tables of Cutting Speeds and Feeds ; Tables for Steel ; for Wrought-iron 69 For Cast-iron ; for Brass ; for Copper ; Speeds where the cuts are unusually long ones 70 CHAPTER III. BORING TOOLS FOR LATHE WORK. Standard Bits and Reamers ; The Shaping of Boring Tools for Lathe Work 71 Pressure on the cutting edge of a Tool, with Illustra- tion of the same 72 Effect of the Application of the Top Bake or Lip to a Boring Tool 74 Shape for the corner of the cutting edge 75 Illustrations of the various forms of Boring Tools for ordinary use 76 Boring Tool for heavy duty on Wrought-iron 77 Boring Tool for Brass 78 Easing a piece of bored Brass or Cast-iron Work, which fits too tight, with a half round Scraper 79 Boring Tools, with Illustrations. 80 Boring Tool Holders 82 CONTENTS. 17 CHAPTER IV. SCREW-CtTTTING TOOLS. Cutting Surfaces of Lathe Tools for cutting Screws; Cutting the Pitch of a Screw which is very coarse. . 84 The most accurate method of cutting small V Threads. 85 Tool for cutting an outside V Thread ; Stout Tool for cutting coarse square Threads on Wrought-iron or Steel 86 Single pointed Tool for cutting an internal Thread; The three diiferent shapes of V Threads in the United States the sharp V Thread, the United States Standard, and the "Whit worth Thread ..... 87 Comparative ease in producing these several Threads . 88 Gauges for testing the angles of Threading Tools ; Meas- uring the Diameter with the Calipers 90 Testing the Pitch of a Thread 91 Centre Gauge and Gauge for grinding and setting Screw Tools 92 Experiments upon Targets representing ship's armor in which the bolts were found unable to resist the shock, and the remedy for the defect ; To calculate the change Gear "Wheels necessary to cut a given Pitch of Thread in a Lathe 94 A simple or single-geared Screw-cutting Lathe 95 Compound or double-geared Screw-cutting Lathe 97 Rule by which to find the number of Teeth in the Wheels to be placed on the Feed Screw 98 Compound Gears common in small American Lathes. . . 100 Pitches of Threads used in France, and the method of finding the necessary change gears; To cut a Double Thread 102 To cut a Treble Screw 103 Hand Chasing 104 To make a Chaser 107 Chaser used on Wrought-iron ; An inside Chaser 110 Yiews of an inside Chaser applied to a piece of work. . . Ill Uses of an inside Chaser ; Cutting inside Threads 113 General directions in cutting Threads 114 18 CONTENTS. CHAPTER V. LATHE DOGS, CARRIERS OR DRIVERS. The Bent-tailed Dog, its objectionable feature, and how it may be obviated ; The Clements Driver 116 Clamp Dog for rectangular or other work, not cylindrical at the driving end ; Form of Driver for driving Bolts ; Adjustable Driver; Wood-turners' Spur centre 119 Screw Chuck for short wood work ; Mandrils or Arbors. 120 Centring Lathe Work ; Centre-grinding device 122 The quickest method of centring Lathe Work 123 Centring Machine ; A centre-drilling attachment for Lathe Work 124 Combined Drill and Countersink for centre drilling; Combined Drill and Countersink, in which a small Twist-Drill is let into the Countersink ; Centre drill- ing by hand 125 Work requiring to be run very true ; A square centre ; To recentre work that has already been turned. 126 Roughing out work which requires to be turned at both ends ; Finishing Lathe Work 127 Emery Cloth and Paper 128 Grinding Clamps for finishing work to gauge diam- eters ; Arbor for grinding out Bores 130 Lathe Chucks; The three classes of Chucks; Horton two jawed Chuck ; Box body Chuck ; Three and four-jawed Chucks 131 The Sweetland Chuck 133 Drill Chuck of the Russell Tool Co 134 Chuck Dogs 135 CHAPTER VI. TURNING ECCENTRICS. Chucking an Eccentric which has a hub or boss on one side only of its bore 136 Chucking an Eccentric having a large amount of throw upon it 138 Turning Crank 140 CONTENTS. 19 To Chuck a Crosshead 141 Counterbalancing work 143 Boring Links or Levers 144 Turning Pistons and Rods 145 Piston Rings 14ti Expanding Chuck for holding Piston Rings or similar work 150 CHAPTER VII. HAND TURNING. One of the most delicate and instructive branches of the Machinist's art 151 Far more instructive to a beginner than any other branch ; Chucking 153 Roughing out ; The Graver 154 Holding the Graver 156 The Heel Tool 157 Hand-turning Brass work 159 Scrapers 160 CHAPTER VIII. DRILLING IN THE LATHE. Work in which the Lathe is resorted to for drilling purposes 164 Half-round Bits 166 Bit in which a Segment has been cut out to admit a Cutter 167 Cutter and Bar designed for piercing holes out of the solid and of great depth ; Flat Drill to enlarge and true them out 168 Drill-holder 170 Reamers , 171 Method of Grinding a Reamer 172 Importance of maintenance of the Reamer to Standard Diameter 174 Reamer which may be adjusted to size by moving its teeth ; Adjustable Reamer for very small work 175 Shell Reamers . 176 20 CONTEXTS. CHAPTER IX. BORING BARS. Importance of the Boring Bar ; Smaller sizes of Boring Bar usually simple parallel Mandrils 178 Boring Bar Cutters requiring to be Adjustable 179 No Machine using a Boring Bar should be allowed to stop while the finishing cut is being taken 180 A rude form of Head : 181 Position which Cutters should occupy towards the head or Body of the Bar 183 Small Boring Bars '. . . 189 CHAPTER X. SLOTTING MACHINE TOOLS. Two Classes of Tools used in Slotting Machines 191 Tool for cutting a Half-round Groove, holding Bar and Short Tool 192 Knife Tool for heavy work 193 CHAPTER XI. TWIST DRILLS. The Cutting Edges of Brills, with various examples 197 Testing Drills 199 The Flat Drill 201 To increase the Keenness of a Flat Drill; Feeding Drills 202 The Farmer Lathe Drill ; Experiments of Wm. Sellers & Co. with a Flat Drill 204 Drilling Hard Metals 205 Slotting or Keyway Drills 206 Pin Drills 211 Countersink Drills 212 Cutters 214 CONTENTS. 21 CHAPTER XII. TOOL STEEL. Cutting Tools for .all machines should be made of hammered Steel 219 Forging Tools 220 Tool hardening and tempering 222 Hardening ; To harden Springs 227 Case-hardening Wrought-iron 229 The wear of metal surfaces 230 Annealing or Softening 236 Mixtures of Metals 237 CHAPTER XIII. TAPS AND DIES. Forging of Taps 238 The Nut Tap 240 Taps having taper in the diameter of the bottom of the Thread; Proper taper for Hand and Machine Taps 241 Taps having Thread on the small end of the Taper; Turning the plain part of a Tap ; Taps for use in holes to be tapped deeply ; Finishing the Threads of a Tap 242 Flutes of small Taps ; United States Standard for Threads, adopted by the Franklin Institute 243 English or Whitworth Standard ; Hardening Taps 244 Taps of three and of four Flutes 246 The Whitworth, the Brown & Sharpe, and the Pratt & Whitney Taps ; The position of the Square with re- lation to the cutting edges in Hand Taps 248 Adjustable Dies 250 Dies for use in Hand Stocks 251 CHAPTER XIV. VISE-WORK TOOLS. Chisels ; Flat Chisels 256 22 CONTENTS. The Koimd-nosed Chisel ; The Oil-groove Chisel 262 The Diamond-point Chisel 263 The Side Chisel ; Application of Chisels ; Calipers 264 The Square 267 The Scribing Block 268 Files and Filing ; Fitting Files to their handles ; Select- ing a File ; Half-round Files 269 Holding Files 270 Filing out Templates 272 Scrapers and Scraping 280 Vise Clamps 281 Vise-Work Pening 282 Fitting Brasses to their boxes 284 Fitting Link Motions 28 > Fitting Cylinders 288 Scraped Surfaces 297 To make a Surface Plate 301 To cut hard Saw Blades ; To refit leaky Plugs to their Cocks 304 Refitting work by Shrinking it , 308 Steam and Water Joints 313 CHAPTER XV. FITTING CONNECTING RODS. The mode of proceeding with the work 314 To get the length of a Connecting Rod ; To ascertain when the Crank of a Horizontal Engine is upon its exact dead centre 319 Fitting a Connecting Rod 320 The Oil-Hole of a Connecting Rod ; The Brasses or Side Rod 322 Drifts ; Smooth and toothed or cutting Drifts 325 Reverse Keys ,329 Setting Line-shafting in Line 331 CHAPTER XVI. MILLING-MACHINES AND MILLING-TOOLS. Importance of the Milling-machine. . . : 338 Cutting out a Corrugated Surface 339 CONTENTS. 23 Advantage of Milling-tools ; To Mill the Side Faces of a Rod with Milling-bar and Cutters 340 Examples of work with the Milling-machine 341 The Side Faces of the Cutters 343 Use of Milling-tools for cutting the Thread on Taps; Making the Milling-cutters . . .- 344 Finishing the Cutter in the Lathe with an Emery Wheel 3?5 The Teeth of long Cutters 346 CHAPTER XVII, GRINDSTONE AND TOOL GRINDING. Uses of Grindstones; Various kinds of Grindstones; Dry Grinding 347 Qualities of different Grindstones ; Treatment of Grind- stones 348 To make a Grindstone run true ; Accurate Grinding ; Truing up a Grindstone for Tool Grinding 349 Objections to the intermittent truing of a Grindstone ; Device for keeping a Grindstone continuously true 350 Face of a Grindstone for Flat Surfaces ; Positions for holding Tools in Grinding 352 A Feather Edge on a Tool 353 A Device called a Best 359 CHAPTER XVIII. LINING OR MARKING OUT WORK. Importance of Lining Out Work 360 Principles involved in Marking Out Work ; Qualities necessary for a Marker Out 361 To mark an Ellipse 363 To find Points through which the Curve of an Ellipse may be drawn 364 Tools employed by a Marker Out 365 To divide a straight line into two equal parts ; To di- vide a straight line into a number of equidistant points S67 Measuring Work to be Marked Out ; Practice of Mark- ins Out.. 369 24 CONTENTS. To Mark Off an Engine Guide Bar 373 Use of the Compass Calipers in Marking Out Work. . . 376 Philosophy of Marking Out Holes in a certain manner. 377 Centrepunch Marks 378 To Mark Off the Distance between the Centres of two Hubs of unequal height 379 Marking Holes at a right angle 381 To Line Out a Double Eye 383 Marking Out an Eccentric 389 Lining Out Connecting Rods 396 To Mark Off Cylinder Ports and Steam Valves 406 Valve Seats 407 To Mark Out a Cone Pulley 408 CHAPTER XIX. To CALCULATE THE SPEED OF WHEELS, PULLEYS, ETC. CHAPTER XX. How TO SET A SLIDE VALVE. Considerations in Setting a Slide Valve 414 Practical Operations in Setting a Valve 415 CHAPTER XXI. PUMPS. Suction Pumps 423 Force Pumps 425 Piston Pumps 426 A Plunger Pump 427 Efficiency of a Pump, how increased 428 Causes of loss of efficiency in Pumps 430 INDEX.. . 433 THE COMPLETE PRACTICAL MACHINIST. CHAPTER I. CUTTING TOOLS FOR LATHES AND PLANING MACHINES. THE lathe is the most important of all metal-cutting machines, or machine tools as they are termed, not only he- cause of the comparative rapidity of its action, but also from the wide range and variety of operations that may be per- formed in it. He who is an expert lathe hand, or turner, will find but little difficulty in operating any other metal- cutting machine tool, because the methods of holding work and the shapes of the tools for other metal-cutting machines are similar, and are governed by the samo principles as in the case of lathe work ; hence, in this book all tools that are used in the lathe will be discussed under the head of lathe tools, notwithstanding that they may be also used in other machines. Cutting tools for lathes, planing machines, etc., etc., are made of a special grade of cast-steel known as tool steel. The tool is first forged to shape, and then hardened by heating it to a red heat and dipping it in water. Lathe-cutting tools may be divided into two principal classes, viz., slide-rest tools and hand tools. The latter, however, have lost their former importance, because even small lathes are now provided with means to traverse the tools to the cut. 3 (25) 26 COMPLETE PRACTICAL MACHINIST. Slide- rest tools may be subdivided into two classes, those for inside or internal work, and those for external or outside work. They are designated from either the nature of the duty they perform, or from some character- istic peculiar to the tool itself. Thus a side tool is one that cuts upon a side or end face ; a front tool is one that cuts in front ; a spring tool is one that admits of deflection or spring, and so on. In forming cutting tools it will be found that a very slight variation of shape, or of presentment to the work, causes appreciable difference in its cutting capacity, whether for smoothness or in taking off a quantity of metal. Furthermore, the shape of the tool mr.st not only be varied for different kinds of metal, but also for extremo differen-ces of hardness in the same kind of metal, moro notably in the case of steel, some of which is almost as soft as wrought-iron, while the finer grades are exceedingly hard, especially when cut from the bar and not annealed or softened by being brought to a red heat and left to cool slowly. Cast-iron also is sometimes exceptionally hard, requiring a special shape of tool, while wrought-irou and. brass vary but very little in their degree of hardness. The manner in which a lathe tool cuts the metal from the work when fed along it is shown in Fig. 1, which rep- resents a tool feeding a cut along a piece of wrought-iron, and it will be seen that the cutting comes off in a spiral. The diameter and the openness of this spiral depend en~ tirely upon the shape of the tool, so that from the ap- pearance of the cutting the quality of the tool may be judged. The principles which govern the shape of tool necessary to cut a piece of metal under any given condition are general in their application ; so that when these conditions are clearly understood it becomes a comparatively easy matter to shape a tool suitable for them. The principal consideration in determining the proper CUTTING TOOLS. 2Y shape of a cutting tool, for use in a lathe or planer, is where it shall have the rake necessary to make it keen Fig. 1. WORK TOOL enough to cut well, and yet be kept as strong as possible ; and this is governed, in a large degree, by the nature of the work on which it is to be used. It is always desirable, circumstances permitting, to place nearly all the rake or Fig. 2. keenness on the top face of the tool, as shown in Fig. 2, in which D is the top face, and B the bottom one; lines A A and E E representing the level of the top and bot- 28 COMPLETE PRACTICAL MACHINIST. torn of the tool steel, and C a line at a right angle to E, or what is the same thing, to A. The tool in Fig. 3 cor- Fig. 3. responds to that in Fig. 2 so far as its cutting qualifica- tions are concerned, there being merely a slight difference in the forged shape, but not in the cutting edges. That shown in Fig. 3 is called a "diamond point," from the diamond shape of its top face, while that in Fig. 2 is called a " front tool;" the former being more suitable for small, and the latter for large work. Referring now to the top face a, its angle or rake is its incline in the direction of the arrow in Fig. 4. In (hose Fig. 4. (to be hereafter specified) in which top rake is, from the nature of the work to be cut, impracticable, it must be taken off and the tool given the necessary ke.enness by increasing the rake or angle of the bottom or side faces in LATHE AND MACHINE TOOLS. 29 the direction shown in Fig. 5, in which letter b represents u side or bottom face of the tool, its amount of rake being denoted by its angle in the direction of the arrow. Fig. 5. These top and side faces, taken one in conjunction with the other, form a wedge, and all machine tools are nothing more than cutting wedges, the duty performed by the respective faces depending, first, upon the keenness of the general outline of the top and bottom faces, and secondly, upon the position, relative to the work, in which the tool is held and applied. The strain sustained by the top face is not alone that due to the severing of the metal, but that, in addition, which is exerted to break or curl the shaving, which would, if not obstructed by the top face, come off in a straight line, like a piece of cord being unrolled from a cylinder; button coming into contact with the face of the tool (immediately after it has left the cutting edge), it is forced, by that face, out of the straight line and takes cir- cular form of more or less diameter according to the amount of top rake possessed by the tool. The direction of the whole strain upon the top face is at a right angle to it, as denoted in Fig. 6 by the line D, d being the work, B the tool, and C the shaving. It will be readily perceived, then, that if a tool possessing so much top rake is held far out from the tool post or clamp, or is slight in body, any springing of the body of the tool, arising from the pressure due to the cut, will cause the tool point to take a deeper cut, and that the tendency of the strain upon the top face is to draw the tool deeper into its cut. A plain cut (either $* 30 COMPLETE PRACTICAL MACHINIST. inside or outside) admits of the use of a maximum of top rake and of a minimum of bottom rake in all cases when the tool is not liable to spring. Were the strain upon the tool equal in force at all times during the cut, the spring would also be equal, and the cut, therefore, a smooth one ; but in taking a first cut, there may be, and usually is, more metal to be cut off the work in one place than in another; besides which there are inequalities in the texture of the metal, so that when the harder parts come into contact with the tool, it springs more and cuts deeper than it does when cutting the softer parts, and therefore leaves the face of the work uneven. Fig. 6. TOOL The main duty performed by the bottom face of the tool is to support the cutting edge, and the amount of rake it possesses is not, under ordinary circumstances, of very great consequence, so that it be sufficient to well clear, and not rub against the work. It is always desirable, however, to give it as little rake, over and above clearance, as possible, to avoid weakening the cutting part of the tool. When, in consequence of the top face having but very little rake, it becomes necessary to make the general out- line of the tool keen by the application of the maximum of side or bottom rake, the tool becomes proportionately weak, as is shown in Fig. 7; in which a represents the work, B the tool, c the shaving, and D the direction of LATHE AND MACHINE TOOLS. 31 the strain placed upon the top face of the shaving, from which, it will be noted, that the cutting edge is compar- atively weak, and hence, liable to break. Fig. 7. Fig. 8. It follows, then, that if two tools are placed in posi- tion to take an equal cut off similar work, that which possesses the most top rake, while receiving the least strain from the shaving, receives it in a direction the most likely to spring it into its cut. It must not, therefore, be used upon any work having a tendency to draw the tool in, nor upon work to perform which the tool must stand far out from the tool post, for in either case it will spring into its cut. Especially is this likely to occur if the cut has a break in it with a sharply defined edge, such, for example, as turn- ing a shaft with a dovetailed groove in it. Taking all these considera- tions into account, we arrive at the tool shown in Fig. 8, as represent- ing the most desirable amount of top and bottom rake for ordinary purposes on light work ; such a tool is not, however, adapted to taking very heavy cuts, for which duty the top face of the tool is given what is termed side rake. Fig. 9 represents a tool having a maximum of side rake, and therefore designed for very heavy duty, and to be held as close to the tool post as possible. The amount of power required to feed a lathe or other tool into its cut, at the COMPLETE PRACTICAL MACHINIST. Fig. 9. ' same time that the tool is cutting, is considerable when a heavy cut is being taken ; and the object of side rake is not only to make the tool more keen without sacrificing its strength, but to relieve the feed screw or gearing of part of this strain by giving the tool a tendency to feed along and into its cut, which is accomplished by side rake, thus: Fig. 10. Suppose Fig. 10 to represent a tool having side rake its feed being to the left and the pressure of ihe shav- ing will be more sideways. It has in fact followed the LATHE AND MACHINE TOOLS. 33 direction of the rake, decreasing its tendency to run, or spring, in (as shown in Fig. 6), with a corresponding gain in the above-mentioned inclination to feed itself along, Or into, its lateral cut. When side rake is called into use, a corresponding amount of front rake must be dispensed with, or its ten- dency to feed itself becomes so great that it will swing round, using the tool post as a centre, and (feeding rapidly into the cut) spring in and break from the undue pressure, particularly if the lathe or machine has any play in the slides. So much side rake may be given to a tool that it will feed itself without the aid of any feed motion, for the force required to bend the shaving (in heavy cuts only) will react upon the tool, forcing it up and into its cut, while the amount of bottom rake, or clearance as it is sometimes called, may be made just sufficient to permit the tool to enter its cut to the required thickness of shaving or feed and no more; and it will, after the cut is once begun, feed itself and stop of itself when the cut is over. But to grind a tool to this exactitude is too delicate an operation for ordinary practice. The experiment has, how- ever, been successfully tried ; but it was found necessary to have the slides of the lathe very nicely adjusted, and to take up the lost motion in the cross-feed screw. For roughing out and for long continuous cuts, this tool is the best that can be used ; because it presents a keen cutting edge to the metal, and the cutting edge re- ceives the maximum of support from the steel beneath or behind it. It receives less strain from the shaving than any other; and will, in consequence of these virtues com- bined, take a heavier cut, and stand it longer, than any other tool ; but it is not so good for taking a finishing cut as one having front rake, as shown in Fig. 8. Having determined the position of the requisite rake, the next consideration is that of the proper form of the cutting edge, the main principles of which are as follows: COMPLETE PRACTICAL MACHINIST. Fig. 11 is a side and Fig. 12 an end view of a tool having a combination of front and side rake, and it will be understood from what has been already said that the front rake will cause the pressure of the shaving or cutting Fig. 11. Fig. 12. to pull the tool forward and into its cut, while the side rake will act to pull the tool along in the direction of its feed traverse. Now, when the tool is first moved to put on the cut, the cross-feed screw in moving the tool towards the lathe centre will bear on the sides of the threads nearest to the back of the lathe, and if there is any play or lost motion be- tween the threads of the cross-feed screw and its nut, then so soon as the tool edge meets the work the front rake will cause it (under a heavy cut) to move inwards to whatever amount the play in the screw and its nut will permit it to go. Similarly the carriage-moving mechanism will not move the carriage until all the lost motion in its parts is taken up, and when the tool meets the work the strain of a heavy cut will be sufficient from the side rake to pull the tool fur- ward in the direction of the feed, and these two motions CUTTING TOOLS. 35 combined will cause the tool to dig in and probably break. To avoid this difficulty we may adopt two methods : Fig. 13. Fig. 14. first we may take off the front rake, leaving the side rake intact as in the side view, Fig. 13, and the end view, Fig. 14, which will prevent the ten- dency of the tool to move in towards the lathe centre, and next we may set the tool in too far and be winding it outwards with the cross-feed screw at the time the tool- edge first strikes the cut. A better plan, however, is to give the top face negative top rake, as in Fig. 15, from A to B, in which case the pressure of the cut or rather of the cutting on the top face of the tool will act to a great extent to force the tool back and away from Fig. 15. B 36 COMPLETE PRACTICAL MACHINIST. the work, and it will therefore take its cut gradually and easily. Fig. 17. ROUND NOSED TOOLS. Round nosed tools, such as shown in Fig. 16, have a greater length of cutting edge to them (the depth of the cuts being equal) than the more pointed ones, such as was Fig. 16. shown in Fig. 3, and as a result they receive more strain from, aud hence are more liable to run into or out from, the cut. If sufficient rake is given to the tool to obviate this defect, it will, under a heavy cut, spring in. It is, however, well adapted to cutting out curves, or taking finishing cuts on wrought-iron work, which is so strong and stiff as not to spring away from it, because it can be used with a coarse feed without leaving deep or rough tool or feed marks; it should, however, always be used with a slow speed. On coming into contact with the scale or skin of the metal, in case the work will not true up, it is liable to spring away from its cut and therefore to cut deeper into the softer than into the harder parts of the metal. The angles or sides of a cutting tool must not of necessity be quite flat (unless for use on slight work, as rods or spindles), but slightly curved, and in all cases rounded at the point, as in the tool shown in Fig. 17. If the angles LATHE AND MACHINE TOOLS. 37 were left flat and the point sharp, the tool would leave deep and ragged feed marks ; the extreme point, wearing away quickly, would soon render the tool too dull for use, and the point would be apt to break. For finishing small wrought-iron work it should be ground, as shown in Fig. 18, being far preferable to the Fig. 18. square-nosed finishing tools sometimes used for that pur- pose, since such tools do not turn true but follow the texture of the metal, cutting deepest in the softer parts, especially when the tool edge becomes the least dulled from use. It should be used with a quick speed and fine feed. On turning work of one inch and less in diameter, it is an excellent roughing tool, and with the addition of a little side rake is, for work of two inches and less diameter, as good a tool for roughing out as any that can be used. SQUARE-NOSED TOOLS. Square-nosed tools, such as shown in Fig. 19, should never be used upon wrought-iron, steel, or brass, for a broad cutting surface running parallel with the line of feed will always, upon either of these metals, cause the 4 38 COMPLETE PRACTICAL MACHINIST. tool point to spring into the softer parts and to spring away from the harder parts, and, if the tool is liable to spring, in most cases, to dig into the work. Upon cast-iron work, however, such a tool will work to great advantage either for roughing out or finishing. It should be set so that its square nose is placed quite parallel with the work ; Fig. 19. the feed for finishing purposes being almost as broad as the nose of the tool itself, or say three revolutions of the lathe per inch of tool travel. It should be fed very evenly, because all tools possessing a broad cutting surface are subservient to spring, which spring is, in this case, in a direction to deepen the cut ; so that, if more cut is taken at one revolution or stroke than at another, the one cut will be deeper than the other. They are likewise liable to jar or tremble, the only remedy for which is to grind away some of the cutting face or edgo, making it nnrrower. For taking finishing cuts on cast-iron, more top rake may be given to the tool than is employed to rough it out, unless the metal to be cut is very hard ; else the metal will be found, upon inspection, to have numerous small holes on the face that has boon cut, ap- pearing as though it were very porous. This occurs LATHE AND MACHINE TOOLS. 39 because the tool has not cut keenly enough, and has broken the grain of the metal out a little in advance of the cut, in consequence of an undue pressure sustained by the metal at the moment of its being severed by the tool edge. The angle of the top and of the bottom face of a tool does not determine whether it shall act as a scraping or cutting tool, but merely affects its capability of withstanding the strain and wear due to severing the metal which it cuts. Nor is there any definite angle at which the top face, B, to the work converts the edge from a cutting to a scraping one. A general idea may, however, be obtained by reference to Fig. 20, the line A being in each case one drawn from the centre of the work to the point of contact between the tool edge and the work, C being the work, and B the tool. It will be observed that the angle of the top face of the tool varies in each case with the line A. In Fig. 20. position 1, the tool is a cutting one; in 2, it is a scraper; in 3, it is a tool which is a cutter and scraper combined, since it will actually perform both functions at one and the same time; and in 4, it is a good cutting tool, the shapes and angles of the tools being the same in each case. 40 COMPLETE PRACTICAL MACHINIST. Fig. 21. 1 A I It may now be shown that the amount of clearance given by the bottom rake or side rake of a tool depends upon the diameter of the work and the rate of tool feed. In Fig. 21 , for example, we have three tools in positions marked respectively 1, 2 and 3, the amount of rake being such as will give 5 degrees of clearance from the cut in each case. The lines A are at a right angle to the work axis, and we perceive that in position 1 the tool has 8?> degrees of angle from A, while in position 2 it has 10-j, and in position 3, 15 degrees of angle from A. This occurs because the angle of the cut to the work axis is greater in proportion as the diameter of the work is less. It is obvious, therefore, that to give equal clearance, the bottom rake must vary for every different diameter of work or rate of feed. The height of the cutting edge of a tool with relation to the work has an important bearing upon its cutting quali- fications, since it affects the angle of the top face, as may be seen from Fig. 22, in which the tool being placed ex- tremely high, cutting is bent but little out of the straight line. It is obvious, however, that if the conditions are such as to cause the tool to bend under the pressure of the cut and more at one part of a work revolu- tion than at another, then the work would be turned out of true, or out of round, as it is sometimes termed. LATHE AXD MACHINE TOOLS. 41 In Figs. 23 and 24 are two tools of the same shape, but placed at different heights, and it is seen from the dotted Fig. 22. lines that the lower the tool the longer the line of resist- ance of the metal to the cutting action of the tool. Sir Joseph Whitworth designs his lathes so that Fig. 23. the tool requires to be forged as in Fig. 25 to bring its cutting edge level with the axis of the work W, so that if the tool bends under the cut pressure (which it will do to some extent, however rigidly it may be held), it will move in a direction having a minimum of effect upon the roundness of the work. Thus let K represent the lathe rest and A the ful- crum or point off which the tool springs or bends, and the arrow will represent the direction of tool spring. It follows therefore that all tools should be held so that their cutting edges are as near the tool post as possible, so as to avoid their spring- 4 Fig. 24. 42 COMPLETE PRACTICAL MACHINIST. ing, and to check as far as possible their giving way to the cut, in consequence of the play there may be in the slides of the tool rest ; but if, from the nature of the work Fig. 25. to be performed, the tool must of necessity stand out far from the tool post, we should give the tool but little top rake, and be sure not to place it above the horizontal centre of the work, The cutting tools for planing machines are subservient to the same spring, but the effect is Fig. 26. ] ess U pon the work, because if, in con- sequence of the spring or deflection, a lathe tool approaches the w'ork axis say one thousandth of an inch, then the work will be turned smaller in diameter to twice this amount, whereas in a planer tool the work will only be affected to the same amount as the tool deflects. Fig. 26 represents a ff^J planer tool, the point A being the \ Vv^ >r ( fulcrum off which it springs, and the arrow the direction in which the spring occurs. This may be remedied so far as its effect upon the work is concerned by shaping the tool so that its cutting edge falls vertically under the centre of the tool steel, as denoted by the dotted line in Fig. 27, in which case the tool Avill cut very smoothly. ID LATHE AND MACHINE TOOLS. 43 other practfce, and especially for broad finishing tools for cast-iron, the cutting edge is made to stand about Fig. 27. Fig. 28. level with the top of the tool steel, the bottom clearance being a minimum as shown by the line A in Fipr. 2K. 44 COMPLETE PRACTICAL MACHINIST. CUTTING OFF PARTING OR GROOVING TOOLS. Tools that are necessarily slight in form, especially those for use in a planer, are more subservient to the evil effects of spring than those of stouter body; and in light planers, when the tool springs in, the table will sometimes lift up, and the machine become locked, the cut being too deep for the belt to drive. The tool most subservient to spring is the parting or grooving tool shown in Fig. 29, which, Fig. 29. having a square nose and a broad cutting surface placed parallel to the travel of the cut, and requiring at times to be slight in body, combines all .the elements which pre- dispose a tool to spring, to obviate which, it should be placed at or a little below the centre, if used in a lathe uix'ier disadvantageous conditions, and bent similarly to the tool shown in Fig. 27, if for use in a planer, unless under favorable conditions. The point is made thicker to give clearance to the sides, so that it will only cut at the end, and the breadth is left wider than other parts to compensate in some measure for the lack of substance in the thickness. For use on wrought-iron or steel, when the tool is very thin, or when it requires to enter the metal to an unusual depth, or requires to stand far out from the tool post, the tool should be made as shown in Fig. 32, which will obviate the necessity of bending the body of the tool, and prevent it from the digging in and breaking off so com- mon under those conditions. When used upon wrought- LATHE AND MACHINE TOOLS. 45 iron or steel, the cutting point should be freely supplied with oil or soapy water. This tool is obviously fed endways into its cut, as shown in Fig. 30, and for grooving purposes cuts better if it Fig. 30. has its cutting edge set above the work axis, but if the work is to be entirely severed, the cutting edge mast be set level with the work axis, and the feed be very fine towards the last. For brass work the top face should be ground depressed towards the point as shown in Fig. 31, which Fig. 81. THE WORK TUB CUTTING- 46 COMPLETE PRACTICAL MACHINIST. will cause it to cut more smoothly and avoid the jarring or chattering which is otherwise very apt to occur. The spring tool, shown in Fig. 33, is especially adapted to finishing sweeps curves*, and round or hollow corners, and may be used with equal advantage on any kind of Fig. 32. metal whatever, performing its duty more perfectly than any other form of tool could, since the conditions under which it operates, that is, a very broad cutting surface, would cause any other tool to dig into the work. The spring tool, however will spring rather away from than into its cut, the only objection to its use being that in consequence of this qualification it is apt to spring into the softer and away from the harder parts of the metal. Its capability, however, to take a broad surface of cut, LATHE AND MACHINE TOOLS. 47 when the cutting edge stands a great way out from tho tool post, renders its use for some work imperative as a finishing tool, while under ordinary conditions it will per- form its duty sufficiently accurately for all practical pur- poses. As illustrated, its top face has a little rake to fit it for use on wrought-iron ; for use on brass and cast-iron the top face should have negative top rake. In cases where the conditions render it liable to spring, the horizontal level of the top face may be made even with the bottom face of the body of the tool, or the body of the tool may be bent for the reasons explained by Figs. 25, 26, and 27. and the accompanying explanations. The top face of a spring tool should be filed up very smoothly before being hardened, and it should never be ground upon that face. The bevel in the direction of the arrow should be less for cast-iron and brass than for other metals, but should in no case be excessive, whatever the inclination of the top face may be. The bend of the tool should be left soft, the cutting face being hardened to a straw-color for stout tools, and a brown for slight ones. The face denoted by the arrow should, after grinding, be smoothed with an oilstone. For use on steel and wrought- iron, it should be freely supplied with either soapy or other water ; and for finishing cast-iron, such water may also be used; and that metal will cut as clean and as polished as wrought-iron, providing the speed at which it is cut is a very slow one. When this tool is to be used a very long way out from the tool post, the wooden wedge, shown driven in the bend, should be taken out. SIDE TOOLS FOR IRON. Side tools for iron are subject to all the principles already explained as governing the shapes of front tools, and differ from them only in the fact that the cutting end of the tool is bent around to enable the cutting edge on one side to cut a face on the work which stands at right angles 43 COMPLETE PRACTICAL MACHINIST. with the straight cut. A front tool is used to take the straight cut nearly up to the shoulder; then a side tool is introduced to take out the corner and cut the side face. Fig. 34. A side tool, whose cutting end is bent to the left, as in Fig. 34, is called a left-handed side tool ; and one which is bent to the right, a right-handed side tool. The cutting edges should form an acute angle, so that, when the point of the tool is cutting out a corner, either the point only or one edge is cutting at a time ; for if both of the edges cut at once, the strain upon the tool causes it to spring in. For heavy work it may be made more round-nosed, and allowed to cut all round the curve, and with a coarse feed. It is also an excellent tool for roughing out sweeps or curves ; and for use on small short bolts, it may be used on the parallel part as well as under the head. For taking out a corner or fillet in slight work, which is liable to spring from the pressure of the cut the point must be rounded very little, and the fillet be shaped by operating the straight and cross feed of the lathe. It is made right or left-handed by bending it in the required direction, that shown being a left-handed one. The form of side tool shown in Fig. 34 is that most de- sirable for all small work where it can be got in ; and in the event of a side face being very hard, it possesses the advantage that the point of the tool may be made to enter LATHE AND MACHINE TOOLS. 49 the cut first, and, cutting beneath the hard skin, fracture it off without cutting it, the pressure of the shaving on the tool keeping the latter to its cut, as shown in Fig. 35. Fig. 35. a is the cutting part of the tool ; B is a shaft with a collar on it ; e is the side cut being taken off the collar, and D is the face, supposed to be hard. The cut is here shown as being commenced from the largest diameter of the collar, and being fed inwards so that the point of the tool may cut well beneath the hard face D, and so that the pressure of the cut on the tool may keep it to its cut, as already explained ; but the tool will cut equally as ad- vantageously if the cut is commenced at the smallest diam- eter of the collar and fed outwards, if the skin, D, is not unusually hard. Fig. 36. For cutting down side faces where there is but little room for the tool to pass, the tool shown in Fig. 36 is used, a being the cutting edge. Not much clearance 5 is 50 COMPLETE PRACTICAL MACHINIST. required on the side face of this tool, its keenness being given by the angle of the top face. Fig. 37 represents an end view of the tool Fi 9- 37 - at work. AY hen the work is of small diameter, the cut- ting edge may be ground straight and set at a right angle to the work axis, so that the tool may be set in its full depth and fed later- ally. In the case of work of large diameter, however, the tool should be formed and set as in Fig. 38, the cut being taken at the point E and fed from the circumference to the centre of the work. In some cases this tool is forged as in Fig. 38, being thicker at the bottom ; this, however, is only advantageous when heavy cuts are taken and greater strength is there- fore necessary. For small work, such as facing under the heads of bolts, the cutting end is bent at an angle, so that the tool will clear the work driver when set as in Fig. 39. FRONT TOOL FOR BRASS WORK. The main distinction between tools for use on iron or steel, and those for use on brass work is, that the latter do not require any top rake. Fig. 40 represents a front tool for brass, and Fig. 41 shows the manner in which the cuttings fly off if the work is run as fast as it should be. The distance the cuttings will fly after leaving the tool gives a very good indication of the efficiency of the tool ; ordinary composition brass flying 15 or 20 feet. The front tool is a complete master tool, filling every qualifi- LATHE AND MACHINE TOOLS. 51 cation for all plain outside work, both for roughing out and finishing. For very light work, or when the tool must be held far out from the tool-post, it may be given Fig. 38. TOOL a little more rnke on the bottom or side faces ; while for finishing, the point may be more rounded and used with a coarser feed, providing the tool is rigid and not liable to spring. When held far out from the tool-post, the side 52 COMPLETE PRACTICAL MACHINIST. Fig. 39. Slide Rest Fig. 40. Fig. 41. LATHE AND MACHINE TOOLS. 53 faces may be ground keener, and the top face have negative top rake that is to say, some of the rake may be ground off the top face, and more given to the bottom or side faces ; under such conditions, also, the cutting sur- face on the point of the tool may be reduced as small as convenient, so as to avoid the liability to spring. When ground round-nosed and smoothed with an oilstone, this tool gives a true ami excellent finish to plain work. SIDE TOOL FOR BRASS WORK. The best side tool for brass is that shown in Fig. 42. It requires little or no top rake, and but little side or bottom rake unless used upon very slight, work, or used Fig. 42. under conditions rendering it liable to spring. For tak- ing out corners, and for turning out recesses which do not pass entirely through the metal, it has no equal. When it is held far out from the tool-post, it should have the top face bevelled off, at an angle of which the cutting part is the lowest, which will thus prevent it from jarring or chattering, and from springing into the work. In grinding it, only the end should be ground, so that the curve of the side of the tool which is intended to allow the body of the tool to clear the shoulder or flange of the work shall be preserved. It will take a parallel cut, provided the corner is slightly rounded, as easily and well as a side cut; and for small work, can be used to advantage for both purposes. 54 COMPLETE PRACTICAL MACHINIST. It is a far better tool than those bent around at the end after the manner of a boring tool, being easier to forge, easier to grind, and not so liable to either spring, jar, or chatter. If a tool for use on brass be made too keen, it will give the surface of the brass a mottled appearance, the color appearing lighter in patches. Furthermore, the face of the cut will appear jarred or chattered, and the cutting must be performed at a slower speed and feed. SPECIAL FORMS OF LATHE TOOLS. When it is required that a lathe tool shall produce upon a number of pieces of work, a sweep curve or fillet that must be of the same form in all the pieces, the diffi- culty arises that it is troublesome to grind the tool with- out altering its shape. This, however, may be avoided by the use of circular cutters, such as shown in Fig. 43, in Fig. 43. which the cutter is cylindrical, and has at the corner the reverse of the curve it is required to produce on the work. The cutter is sharpened by grinding the horizontal face C which is set level with the face A of the holder, this face being made level with the line of lathe centres, when the holder lies horizontal in the tool clamp or tool post. Clearance is obtained partly by reason of the curve of the cutter, and partly by inclining the face B against which the cutter is bolted. LATHE AND MACHINE TOOLS. 55 Figs. 44 and 45 show an application of a cutter of this kind for cutting a thread, it being obvious that to cut a right-hand thread on the work, a left-hand one must be provided on the cutter. TOOL-HOLDERS. To avoid the trouble of forg- ing tools and to give greater rigidity to the tool when it re- quires to stand far out from the tool-post or clamp, various forms of tool-holders are em- ployed. Thus in Fig. 46 is a tool-holder consisting of a bar A having a hub or boss H, an end view of the same being given iii Figs. 47 and 48, in which it is seen that the tool is com- posed of a triangular piece of steel held between two pieces that fit inside the hub of the holder, and are clamped against the tool by a set screw. The tool and these pieces may be revolved in the hub to set the tool at any required angle as in screw cutting. Fig. 49 represents a tool-holder H, having a clamp C secured by the bolt B, and having a feather at/, to hold the clamp horizontal when bolt B is loosened. The tool T has a groove on its side receiving a feather K, which is fast in the holder, and therefore holds the tool at a con- stant angle. At S is a screw threaded into the edge of the tool T, so that by operating this screw the height of the tool may be regulated. By this means the tool may CUTTER 56 COMPLETE PRACTICAL MACHINIST. Fig. 45. Fig. 47. LATHE AND MACHINE TOOLS. 57 Fig. 48. be made to any required shape, and as it is sharpened by grinding the top face only, this shape will be maintained as long as the tool lasts. Figs. 50, 51, 52 and 53 represent Wood bridge's patent tools and tool- holder. The tools consist of straight pieces of steel bevelled at the top to give a certain amount of side rake, the only grinding required to sharpen them being on the Fig. 49. 58 COMPLETE PRACTICAL MACHINIST. end face. The tools are hardened throughout, and hence, require neither forging nor tempering. For left-hand tools the holder is turned end for end, so that the tool may be sustained by the holder as near to the cutting edge as pos- sible, as is shown in Fig. 52, which represents a right and Fig. 50. a left-hand tool in place. The cap which sets over the tool and receives the set screw pressure binds at B, Fig. 53, only, Fio. 51. and the seat A in the holder is at an angle so as to give the side J of the tool the necessary clearance. LATHE AND MACHINE TOOLS. 59 Fig. 54 represents a combined cutting off tool-holder and steadying device which is intended for cutting from rods pieces of an exact length. The holder is secured Fig. 52. Fig. 53. in the tool-post, and has three screws which are set to steady the rod (which of course passes ttirough them). Fig. 54. On the side of the holder is a slideway carrying a slide to which the cutting-off tool is fixed, being fed to its cut by the crank handle shown. Fig. 55 represents a -* 55. cutting-off device in which one leg or arm carries steadying pieces adjusted by means of the thumb 60 COMPLETE PRACTICAL MACHINIST. screw shown, while the other arm carries a gauge and a pivoted piece carrying the cutting tool, which is fed to the cut by the second arm, which is pivoted to the first one. This affords a very ready means of cutting off pieces for small work, since it squares the work ends at the same time that it cuts it off. Fig. 56 represents a tool-holder for a shaping machine, Fig. 56. the tool being carried in a tool-post at the back of the holder so that it is pulled rather than pushed to its cut, and is not so liable to dip into the work from the spring or deflection. In place of a tool-post the tool or cutter may for curves, fillets, etc., be bolted direct to the holder, as in Fig. 57, B representing the cutter. Fig. 58 repre- sents another form of tool-holder for shaping or planing machines, the tool being carried in a pivoted tool-post at the end of the holder, so that it may be swung to the right or left as may be required ; a side and a front view of this tool and holder in place upon the planing machine sliding head, is shown in Fig. 59. The tool is set at an angle to give it front rake. The objection to this form is that the tool is partly hidden by the tool-post. Applications of LATHE AND MACHINE TOOLS. 61 this tool-holder are shown in Fig. 60, the direction of the feed being denoted by the arrows. Fig. 61 represents an Fig. 57. o o exceedingly useful form of tool-holder for planing machine tools, applications of its use being shown as follows. Figs. 62, 63, 64 and 65 show the application of such a Fig. 58. holder and tools to the cutting out of a T-shaped groove from solid metal. A grooving tool first cuts two grooves, as shown in Fig. 62. where one groove is shown finished 6 62 COMPLETE PRACTICAL MACHINIST. and the tool is in operation on the second one. The next operation would be to cut out the metal between these two Fig. 59. grooves, using the same tool. In the absence of the holder a bent tool, such as in Fig. 63, would be required to cut Fig. 60. these grooves, and the tool being less rigid would not be able to carry so heavy a feed, nor would it produce so LATHE AND MACHINE TOOLS. 63 smooth a cut. This groove being finished, a tool having a single bend may be used to cut out the enlargement on one side, as shown in Fig. 64, carrying down Fig. 61. a groove at each end, and then cutting out the metal left between them. In the ab- sence of the holder the tool would require to have two bends, as shown in Fig. 65, and beiag made of large steel would be more difficult to forge and troublesome to use on account of its liability to spring and bend under the pressure of the cut, whereas, on account of the stiffness of the holder, its tools may be made of small pieces of steel. Fig. 62. Fig. 63. Fig. 64. Fig. 65. CHAPTER II. CUTTING SPEED AND FEED. THE term " cutting speed," as applied to machine tools, means the number of feet of cutting performed by the tool edge, in a given time, or what is the same thing, the number of feet the shaving, cut by the tool in a given time, would measure if extended in a straight line. The term " feed," as applied to a machine tool, means the thick- ness of the cut or shaving taken by the tool. Planing machines being constructed so that their tables run at a given and unchangeable speed, their cutting speed is fixed ; and the operator has only, therefore, to consider the question of the amount of feed to be given to the tool at a cut, which may be placed at a maximum by keeping the tool as stout as possible in proportion to its work, making it as hard as its strength will allow, and fastening it so that its cutting edge will be as close to the tool post as circumstances will permit. In all cases, however, cast- iron may be cut in a planer with a coarser feed than is possible with wrought-iron. Milling machines should have their cutters revolve so that the cutting speed of the largest diameter of the cutter does not exceed 18 feet per minute, at which speed the cut taken may be made, without injury to the cutter, as deep as the machine will drive. It is only when we treat of lathe work that the questions of feed and speed assume their real importance, for there is no part of the turner's art in which so great a variation of practice exists or is possible, no part of his art so intricate and deceptive, and none requiring so much judgment, per- ception, and watchfulness, not only because the nature of f>4 CUTTING SPEED AND FEED. 65 the work to be performed may render peculiar conditions of speed and feed necessary, but also because a tool may appear to the unpractised or even to the experienced eye, to be doing excellent duty, when it is really falling far short of the duly it is capable of performing. For all work which is so slight as to be very liable to spring from the force of the cut, for work to perform which a tool slight in body must be used, and in cases where the tool has to take out a sweep or round a corner which has a break in it, a light or fine feed must be employed ; and it is there- fore advisable to let the cutting speed be as fast as the tool will stand. But under all ordinary circumstances, a maxi- mum of tool feed rather than of lathe speed will perform the greatest quantity of work in a given time. A keen tool, used with a quick speed and fine feed, will cut off a thin shav- ing with a rapidity very pleasing to the eye, but equally as deceptive to the judgment; for under such a high rate of cutting speed, the tool will not stand either a deep cut or a coarse feed ; and the increase in the depth of cut and in the feed of the tool, obtainable by the employment of a slower lathe speed, more than compensates for the reduc- tion of lathe speed necessary to their attainment, as the following remarks will disclose. Wruught-iron, of about two inches in diameter, is not uncommonly turned with a tool feed of one inch of tool travel to 40 revolutions of the lathe. With a tool feed as fine as this, it is possible, on work of this size, to employ a cutting speed as high as 27 feet per minute, providing the depth of the cut does not exceed one-eighth of an inch, reducing the diameter of the work to If inches. The length of shaft or rod turned under such circumstances will be l^ inches per minute, since the lathe speed (neces- sary to give the tool a cutting speed of 27 feet per minute) woul.l require to be about 51 revolutions per minute; and as each revolution of the lathe moves the tool forward ^ of au inch, the duty performed is |J of an inch, or 1 3 9 2 6' 66 COMPLETE PRACTICAL MACHINIST. inches of shaft turned per minute, as before stated. If, however, we turn the same rod or shaft of two inch iron, with a lathe speed of 36 revolutions per minute, and a tool travel of one inch to 24 revolutions of the lathe, the amount of duty performed will be || inches, or li inches of shaft turned per minute. Here, then, we have a gain of about 17 per cent, in favor of the employment of the slow speed and quick feed. Nor is this all, for we have reduced the cutting speed to 19 feet, instead of 27 feet per minute, and the tool will, in consequence, stand the cut much longer and cut cleaner. Pursuing our investigations still further, we find from actual test that, cutting at the rate of 27 feet per minute, the tool will not stand a cut deeper than one-eighth of an inch ; whereas under the cutting speed of 19 feet per minute, it will take a cut of one-quarter of an inch in depth, thus considerably more than doubling the duty per- formed by the tool, in consequence of the decreased cutting speed and increased feed or tool travel. Lathe work of about three-quarters of an inch in diameter may, if there is no break in the cut, be turned at a cutting speed of as much as 36 feet per minute, the feed being one inch of tool travel to about 25 revolutions of the lathe. The revolutions per minute of the lathe, necessary to give such a rate of cutting speed, will be about 183; the duty per- formed will therefore be V^or 7 T 5 g inches of three-quarter inch iron turned per minute. A feed of one inch of tool travel to 25 revolutions of the lathe is greater than is gen- erally employed upon work of so small a diameter as three- quarter inch, but is not too great for the generality of work of such a size ; for the tool will stand either a roughing or smoothing cut at that speed, unless in the exceptional case of the work being so long as to cause it to spring away from the tool. Under these circumstances the feed may be re- duced to one inch of tool travel to 30 or 40 revolutions of the lathe, according to the length and depth of the cut. CUTTING SPEED AND FEED. 67 It will be observed that the cutting speed given, for work of three-quarter inch diameter, is nearly double that given as the most advantageous for work of two inches diameter, while the feed or tool travel is nearly the same in both cases ; the reason of this is that the tool can be ground much keener for the smaller sized than it could be for the larger sized work, and, furthermore, because the metal, being cut off the smaller work, is not so well supported by the metal behind it as is the metal being cut off the larger work, and, in consequence, places less strain upon the tool point, as illustrated in Figs. 66 and 67. Fig. 67. B is a shaft, and C is the tool in both cases. The dotted line a, in Fig. 66, does not, it will be observed, pass through so much of the metal of the shaft B, as does the dotted line a, of the shaft B, in Fig. 67. The metal in contact with the 68 COMPLETE PRACTICAL MACHINIST. point of the tool in Fig. 66, is not, therefore, so well sup- ported by the metal behind it as is the metal in contact with the point of the tool in Fig. 67, the result being that the tool, taking a cut on the smaller shaft equal in depth to that taken by the tool on the larger one, may have a higher rate of cutting speed without sustaining any more force from the cut, the difference in the resistance of the metal to the tools being equalized by the increased speed of the smaller shaft. These conditions are reversed in the case of boring, the metal, being cut in a small hole, being better supported by the metal behind it than is the case in a larger hole or bore. This may be overcome by making the boring tool point cut b^low the horizontal centre of the work, while the body of the tool may, to keep it stout enough, be kept in the centre of the hole. But in a large bore, the effect is not so seriously encountered, because of the nearer approach of the circle to the straight line. On heavy work it is specially desirable to have the tool stand a long time without being taken out to grind, for the following reasons : 1. It takes longer to stop and start the lathe, and to take out and replace the tool. 2. It takes longer to readjust the tool to its cut. 3. It takes more time to put the feed motion into gear again. 4. The feed motion is very slow to travel the tool up and into its cut, and to take up its play or lost motion. 5. Lastly, the tool should take a great many more feet of cut, at one grinding, than is the case with a tool for small work. A tool used on work 5 inches diameter (the lathe making 20 revolutions to feed the tool one inch) would perform 314 feet of cutting in travelling a foot, the lathe having, of course, performed 240 revolutions ; while one used on work 10 feet in diameter (with the same ratio of speed) will have performed 314 feet of cutting when the tool has travelled half an inch, and the lathe made 10 revolutions only. In practice, howev?r, the feed for larger work is increased CUTTING SPEED AND FEED. in a far greater ratio than the cutting speed is diminished, as compared with small work; but in all cases the old axiom and poetical couplet holds good, that "A quick feed And slow speed " are the most expeditious for cutting off a quantity of metal, and in the case of cast-iron, for finishing it also. A positive or constant rate of cutting speed for large work cannot be given, because the hardness of the metal, the liability of the work to spring in consequence of its shape, the distance of the point of the tool from the tool post, aud other causes already explained, may render a deviation necessary, but the following are the approximate speeds and feeds for ordinary work : TABLES OF CUTTING SPEEDS AND FEEDS. Table for Steel. ROUGHING CUTS. FINISHING CUTS. Diameter of work in inches. Speed in feet per minute. Feed. Speed in feet per minute. Feed. 1 and less 20 25 20 30 1 to 2 18 25 18 30 2 to 3 18 25 15 80 3 to 6 15 20 15 30 For Wrought-Iron. ROUGHING CUTS. FINISHING CUTS. Diameter of work Speed in feet Speed in feet in inches. per minute. Feed. per minute. 1 and less 35 25 38 1 to 2 25 20 30 2 to 4 25 20 25 4 to 6 23 20 23 6 to 12 20 15 23 12 to 20 18 12 18 Feed. 30 30 25 25 ?() 16 70 COMPLETE PRACTICAL MACHINIST. For Cast-Iron. ROUGHING CUTS. FINISHING CUTS. Diameter of work in inches. Speed in feet per minute. Feed. Speed in feet per minute. Feed. 1 and less 38 20 38 ?0 1 to 2 35 20 35 16 2 to 4 30 20 30 10 4 to 6 25 16 25 6 6 to 12 20 14 20 6 12 to 20 20 10 20 4 For Brass. ROUGHING CUTS. FINISHING CUTS. Diameter of work in inches. Speed in feet per minute. Feed. Speed in feet per minute. Feed. 25 25 1 and less 1 to 2 120 100 25 25 120 100 2 to 4 80 25 100 25 4 to 6 70 25 70 25 6 to 12 60 25 70 25 For Copper. ROUGHING CUTS. FINISHING CUTS. Diameter of work Speed in feet Speed in feet in inches. per minute. Feed. pei- minute. Feed. 1 and less 350 25 400 25 2 to 5 250 25 300 25 5 to 12 200 25 200 25 12 to 20 150 25 150 30 In cases where the cuts are unusually long ones, the cutting speeds may be slightly reduced except in the case of copper. All the tools we have so far described may justly be termed master tools, for work on external sur- faces, each entirely filling its arena, and all other tools used on outside work are simply modifications called into requi- sition to suit exceptional cases. CHAPTER III. BORING TOOLS FOR LATHE WORK. STANDARD bits and reamers have superseded the use of boring tools for all special and many other purposes, but there are numerous cases where a boring tool cannot be dis- pensed with, especially in repairing shops and for promis- cuous work. Boring tools for use on lathe work require to be shaped with greater exactitude than any other lathe tools, for the reason that they are slighter in body in proportion to the duty required of them than any other; and as a rule, the cutting edges standing further out from the tool post or clamp, the body of the tool is more subject to spring from the strain of the cut. It is obvious that, if the hole to be bored out is a long one, the cutting edge of the tool will become dull at the end of the hole as compared to what it was at the commencement (a remark which, of course, applies to all tools) ; but in tools stout in proportion to the duty required of them, and held close in to the tool post, the effect of the slight wear of the cutting edge, due to a finishing cut, is not practically appreciable. In the case of a boring tool, however, the distance of the cutting edge from the tool post renders the slightest variation in the cutting capability of the tool sufficient to affect the work, as may be experienced by boring out a hole half of its length, and then merely exerting a pressure on the body of the tool, as near the entrance of the hole as possible, with the fingers, when the size of the last half of the hole will be found to have varied according to the direction in 71 72 COMPLETE PRACTICAL MACHINIST. which the pressure was placed. As a result of this extreme sensitiveness to spring, the tool is apt to spring away from the cut as the boring proceeds, thus leaving the hole smaller at the back than at the front end. To remedy this defect, several very fine finishing cuts may be taken ; but a better plan is to so shape the tool that its spring will be in a direc- tion the least liable to affect the size of the bore of the work. The pressure on the cutting edge of a tool acts in two directions, the one vertical, the other lateral. The down- ward pressure remains, under equal conditions, at all times the same ; the lateral pressure varies according to the direc- Fig. 68. tiou of the plane of the cutting edge of the tool to the line or direction in which the tool travels : the general direction of the pressure being at a right angle to the general direction of the plane of the cutting edge. For example, the lateral pressure, and hence the spring of the various tools, shown in Fig. 68, will be in each case in the direction denoted by the dotted lines. D is a section of a piece of metal requir- ing the three inside collars to be cut out; A, B, and C are variously shaped boring tools, from which it will be seen that A would leave the cut in proportion as it suffered from spring, which would increase as the tool edge became dull, and that the cut forms a wedge, tending to force the tool towards the centre of the work. B would neither spring BORING TOOLS. FOR LATHE WORK. 73 into nor away from the cut, but would simply require more power to feed it as the edge became dulled ; while C would have a tendency to run into the cut in proportion as it springs ; and as the tool edge became dull, it would force the tool point deeper and deeper into the cut until some- thing gave way. Now, in addition to this consideration of spring, we have the relative keenness of the tools, it being obvious at a glance that (independent of any top rake or lip) C is the keenest, and A the least keen tool ; and since wrought-iron requires the keenest, cast-iron a medium, and brass the least keen tool, it follows that we may accept, as a rule, C for wrought-iron, B for cast-iron, and A for brass work. To this rule there are, however, variations to be made to suit exceptional cases, such for instance as when. a hole terminates in solid metal and has a flat bottom, in which case the tool B (slightly modified towards the form of tool C) must be employed. Or suppose a hole in cast- iron to be, as is often the case, very hard at and near the surface of the metal. Tool A would commence cutting the hard surface, and, becoming dull, would spring away from the cut in spite of all that could be done to prevent it ; while tool B would commence to cut both the hard and the soft metal together, the cutting edge wearing rapidly away where it came into contact with the hard surface of the metal ; and these conditions would, in both cases, continue during the whole operation of boring, rendering it difficult and tardy. But if the tool C were employed, the point of the tool would commence cutting the soft part of the metal first, and would undermine the hard surface, and (from the pressure) break it instead of cutting it away, as shown in Fig. 69, in which a is the point of the tool, and from a to B is the cutting edge ; the dotted lines, c and D, represent the depth of the cut, c being the inside skin of the metal, sup- posed to be hard. The angle at which the cutting edge stands to the cut causes the pressure, due to the bending and fracturing of 7 74 COMPLETE PRACTICAL MACHINIST. the shaving, to be in the direction of e, which keeps the tool point into its cut ; while the resistance of the tool point to this force, reacting upon the cut, from a to B, causes the hard skin to break away. Fig. 69. When a cut is being taken which is not sufficient to clean up or true the work, less top rake must be given, as a very keen tool loses its edge more quickly than one less keen. The reason for taking the rake off the top of a tool is that, if it were taken off the bottom, the cutting edge would not be so well supported by the metal, and would have a ten- dency to scrape, which rule applies both to inside and out- side cuts. For brass work, top rake is never applied, because it would cause the tool to jar and cut roughly, bottom rake alone being sufficient to give a tool for brass the requisite keenness. The application of top rake or lip to a boring tool lessens the strain due to serving the metal ; by presenting a keener cutting edge, it lessens the tendency to lateral spring, and increases that to vertical spring, and is beneficial in all cases in which it can be employed. Upon wrought-iron and steel it is indispensable ; upon cast it may be employed to a limited degree ; and upon brass it is inadmissible by reason of its causing the tool to either jar or chatter. In Fig. 70, B represents a section of the work, No. 1 represents a boring tool with top rake, for wrought-iron, and No. 2 a tool without top rake, for brass work, which may be also used for cast-iron when the tool stands a long way out from the tool post or clamp, under which circumstances it is SORING TOOLS FOR LATHE WORK. 75 Fig. 70. liable to jar or chatter. A tool for use on wrought-iron should have the same amount of top rake, no matter how far it stands out from the tool post ; whereas one for use on cast-iron or brass requires to be the less keen the further it stands out from the tool post. To take a very smooth cut on brass work, the top face of the tool, shown at 2 in Fig. 70, must be ground off, as denoted by the dotted line. We have now to consider the most desirable shape for the cor- ner of the cutting edge. A posi- tively sharp corner, unless for a special purpose, is very undesira- ble, because the extreme point soon wears away, leaving the cut- ting qualification of the tool almost destroyed, and because it leaves the work rough, and can only be employed with a very fine feed. It may be accepted as a general rule that, for roughing cuts, on brass work, the corner should be sufficiently rounded to give strength to the tool point; while, in finishing cuts, the point may be made as round as possible without causing the tool to jar or chatter. Now, since the tendency of the tool to jar or chatter upon all metals depends upon four points, namely, the distance it stands out from the tool post, the amount of top rake, the acuteness or keenness of the general outline of the tool, and the shape of the cutting corner, it will readily be perceived that considerable judg- ment is required to determine the most desirable form for 76 COMPLETE PRACTICAL MACHINIST. any particular conditions, and that it is only by understand- ing the principles governing the conditions that a tool to suit them may be at once formed. In Fig. 71 will be found the various forms of boring tools for ordinary use. No. 1 is for use when the conditions admit of a heavy cut on wrought-iron. No. 2 is for use on wrought-iron when the tool stands so far from the tool post as to be necessarily subject to spring. No. 3 is to cut out a square corner at the bottom of a hole in wrought-iron. No. 4 is for taking out a heavy cut in cast-iron. No. 5 is Fig. 71. for taking out a finishing cut in cast-iron when the tool is proportionally stout, and hence not liable to spring or chatter : the point being flat, the cutting being performed by the front corner, and the back part being adjusted to merely scrape. No. 6 is for use on cast-iron under con- ditions in which the tool is liable to jar or spring. An inspection of all these tools will disclose that the tool point is more rounded for favorable conditions, that is, when the body of the tool is stout, and the cutting edge is not held far out from the tool post; that, to prevent jarring, the SORING TOOLS FOR LATHE WORK. 77 point of the tool is made less round, which is done to reduce the cutting surface of the tool edge (since it is apparent that, with a given depth of cut, the round-pointed tool will present the most cutting edge to the cut) ; and that, to further prevent jarring or chattering, the leading part of the cutting edge is ground at an angle ; while, as another precaution against that evil, the general form of the tool is varied from that of tool C, in Fig. 68, towards that of tool A in the same figure; while for brass work, no top rake or lip is employed, but the tool is bevelled off to suit those cases in which it is liable to excessive spring. It is obvious that the feed may be coarser for a round-nosed than for a more acute tool, and that, the rounder the nose, the smoother the cut will be with the same rate of feed. For heavy duty on wrought-iron, whether in large or small holes, the boring tool, represented in Fig. 72, has no Fig. 72. equal. The rake on the top face makes the cutting edge per- form its duty on the front edge, and the strain due to bending the shaving tends to draw the tool to its cut, giving it an inclination to feed itself forward, thus relieving the feed screw of a part 'f the duty due to the strain of feeding. The cutting edge should not stand above the horizontal level of the top of the tool body ; otherwise, so stout a tool could not be gotten into a given size of hole ; a consideration which, in small holes, is of the utmost importance. For 78 COMPLETE PRACTICAL MACHINIST. similar duty on brass, the tool shown in Fig. 73 is the best that can be employed. Fig. 73. BORING TOOL FOR BRASS. Fig.74. When, upon brass work, a loring tool has a broad cutting surface, such as is required to cut a recess, the only way to prevent extreme chattering and jarring is to grind oft' the top face, giving it negative top rake, as shown in Fig. 74 : a being a section of the body of the tool, B the cutting part, and c the outline of the hole. B, being the lowest point of the top face, possesses negative top rake, and a corre- sponding tendency to scrape rather than cut keenly. The point B should always be above the centre of the hole, so that, in springing, it will spring away from and not into its cut. A boring tool, slight in proportion to its duty, and for use upon small wrought-iron work, should always be placed so that its cutting edge is a little below the centre of the hole, in which case the bottom of the body of the tool is liable, in small holes, to bear against the bottom of the hole, unless the cutting part is made to be a little below the centre of the body of the tool, rendering it rather difficult to grind on the top face. It is not, however, imperatively necessary to grind it there, since it can be sharpened by grinding the side faces; BORING TOOLS FOR LATHE WORK. 7ft and the advantage gained by being enabled to get, into a given sized hole, a stouter tool than otherwise could be done, and, as a result, to take deeper and more nearly parallel cuts (for such tools generally spring off their cut at the back end of the hole, leaving it taper unless several light cuts are taken out), more than compensates for the extra wear of the tool, consequent upon being able to grind it upon one part only. Boring tools for use on w rough t-iron, cast-iron, steel or copper, require very little side or bottom rake, only suffi- cient, in fact, to well clear the sides of the cut, and the straighter these side faces are kept the stronger the tool ; and the better the cutting edges are supported by the metal behind them, the longer will they stand without regrinding. When boring light brass work, it is well to hold a brush near the entrance of the hole, to prevent the turnings from flying about the shop ; while cutting tools for outside brass work may have a split-leather washer forced over the body near the cutting end for the same purpose. After a piece of brass or cast-iron work has been bored and taken out of the lathe, and is found on trial to fit a little too tight, it may, if it is difficult to chuck it true again, be eased by a half-round scraper, as follows : Take an old half-round, smooth file, and grind the teeth com- pletely out of the flat face ; then grind the edges to an angle sufficiently acute to cut freely, as a scraper ; then rechuck the work in the lathe as nearly true as possible, and revolve it at such a speed that the scraper will cut at about 380 feet per minute ; then apply the scraper edge to the bore of the hole at the bottom, moving it along the bore and holding it firmly. If the flat face and the bevelled edge of the scraper be ground true and even, and care is taken in using it to take out the metal only where required, this tool will perform excellent duty and cut very smoothly. It may also be used to advantage to ease out by hand the 80 COMPLETE PRACTICAL MACHINIST. narrow places of a hole that is oval, or the small end of one that is taper and requires to be made parallel. The smoothness of its work is much improved by smoothing its edge upon an oilstone. Here it may be well to state that the application of an oilstone to the cutting edges of a boring tool increases its tendency to chatter ; if, therefore, a hole requires to be made unusually smooth, the tool BORING TOOLS FOR LATHE WORK. 81 must be given less top rake and may then be oilstoned. In many cases a tool may be prevented from chattering by holding it with the fingers as near the entrance of the hole as possible. Fig. 75 represents a boring tool, composed of a piece of octagon steel lying in a holder or seat E, which may be so set in the tool-post as to support the tool as near to the cutting edge as the depth of the hole to be bored will permit. Fig. 76 represents a boring tool made of round steel, and clamped between two pieces 1 and 2, so that the tool Fig. 76. may be readily adjusted to the work by revolving it ou its axis, and placed to project through the clamps as far as necessary for the work, and to facilitate this the tool is sometimes separate and secured by a set screw. 82 COMPLETE PRACTICAL MACHINIST. BORING TOOL HOLDERS. For use on holes too small to admit of a bar having a sliding head, which are usually bored with a slide rest tool, a boring tool holder may be employed to great advantage. Such a holder may be made by squaring or flattening one end of a round bar of iron so that it will fit into the tool post of the lathe, and cutting into the opposite end a groove to receive a short boring tool, the latter being fastened to its place by set screws provided in the holder or by being wedged in with a small wedge. Various sizes of such holders should be made, the larger sizes being provided with set screws to hold the tool. For use in holes of from two to eight inches bore, such an appliance is invaluable, especially if the hole to be bored is of unusual depth ; because the bar may be made very stout in proportion to the size of the hole, and will, therefore, stand a depth of cut and a rate of feed totally impracticable with an ordi- nary boring tool, and will not spring away from its cut towards the back end of the hole, as boring tools are apt to do. Furthermore, the cutting tools, being small, are easily forged, ground up, and renewed when worn out ; and the bar maintains its original length, which may be made to suit the depth of hole required to be bored ; while a boring tool becomes shorter each time it requires reforging. For truing out broad recesses in large work, the slot in the end may be made large enough to receive two tools, one to turn the inside and the other the outside of the recess. For use upon holes of a very large bore, or upon outside work in which the tool requires to stand a long way out from the slide rest, as sometimes occurs when the diameter of the work is so near the full size, the lathe will swing ; that there is not sufficient room for the slide rest of the lathe to pass under the work, a square tool holder should SORING TOOLS FOR LATHE WORK. 83 be employed, such tool holder being a stout bar of square iron, say 2? inches square, and having a complete tool box on one end, the tool box being provided with two stout steel set screws. CHAPTEK IV. SCREW-CUTTING TOOLS. LATHE tools for cutting screws have necessarily, from the nature of their duty, a comparatively broad cutting surface, rendering them very subject to spring. Those used for V threads, being ground to fit the V of the thread, are, in consequence, weak and liable to break ; to avoid which they should only be given enough bottom rake to clear the thread well, and top rake sufficient to made them cut clean. They are used at a slow rate of cutting speed, and may therefore be lowered to a straw-colored temper (as reducing the temper strengthens a tool). Firmness and strength are of great importance to this class of tool, so that it should be fastened with the cutting edge as near to the tool post as is convenient. For use on wrought-iron, the V or thread-cutting tool is sometimes given side rake ; but this is not a necessity and is of doubtful utility, because the advantage gained by its tendency to assist in feeding itself is quite counterbalanced by its increased liability to break at the point. It should always be placed to cut at the centre of the work. If the pitch of the screw to be cut is very coarse, a tool nearly one-half of the width of the space between one thread and the next should be employed, so as to avoid the spring which a tool of the full width would undergo. After taking several cuts, the tool must be moved laterally to the amount of its width, and cuts taken off as before until the tool has cut somewhat deeper than it did before 84 SCREW-CUTTING TOOLS. 85 being moved, when it must be placed back again in its first position, and the process repeated until the required depth of thread is attained. Fig. 77. Fig. 77 represents a thread or screw during the above described process of cutting, a a a is the groove or space taken out by the cuts before the tool was moved ; B B represents the first cut taken after it was moved ; c is the point to which the cut B is supposed (for the purpose of this illustration) to have travelled. The tool used having been a little less than one-half the proper width of the space of the thread, it becomes evident that the thread will be left with rather more than its proper thickness, which is done to allow finishing cuts to be taken upon its sides, for which purpose the side tool (given in Fig. 36) is brought into requisition, care being taken that it be placed true, so as to cut both sides of the thread of an equal angle to the centre line of the screw. In cutting V threads of a coarse pitch, the tool may be made less in width than the required space between the threads demands, so that it may be moved a little laterally in order to hike a cut off one side of the thread only at a time, by which means a heavier cut may be taken with less liability for the tool to spring in ; but the finishing cut is better if taken by a tool of the full width or shape of the thread. The most accurate method of cutting small V threads 8 8G COMPLETE PRACTICAL MACHINIST. is to use a stout chaser fastened in the tool post, and then feed it with the screw-cutting gear of the lathe, the same as with a common screw-cutting tool. Such a chattr should be made hollow in the length of the tooth, possess a minimum of top rake, and be placed to cut at the centre of the work ; and it should be so placed in the tool post that the teeth stand exactly parallel to the line of the cut Fig 78. Fig. 78 represents a tool for cutting an outside V thread in brass work. When, however, the tool point must, of necessity, stand far out from the tool post, it must be given negative top rake, to make it cut smoothly and prevent its jarring. To adapt this tool to cutting V threads on iron, it is only necessary to give it top rake. Fig. 79. Fig. 79 represents a very stout tool, adapted to cutting coarse square threads on wrought-iron or steel. For cutting square threads on brass work, the tool shown in Fig. 80 should be used. Fig. 80. SCREWOUTTING TOOLS. 87 Fig. 81 represents a single pointed tool, for cutting an internal thread, and it is obvious that in order that it may cut a thread of cor- rect shape, it is necessary to grind the V to a gauge, to set it so that each cutting edge shall stand at an equal degree of angle to the work axis, and also that the cutting edges shall stand level with the centre of the work or line of lathe centres. There are three different shapes of V threads in use in the United States, viz.: first, the Fig. 82. sharp V thread, shown in Fig. 82, in which the thread 38 COMPLETE PRACTICAL MACHINIST. sides meet in a point both at the top and bottom, and these sides are at an angle of 60 degrees to one another. Second, the United States standard, whose form is shown in Fig. 83, which corre- Fig. 83. spends in shape to the above thread, with one-eighth of the top cut off, and one-eighth of the bottom filled in so as to leave a flat place at the top = and bottom of the : -- thread. And third, the Whitworth thread shown in Fig. 84, in which the angle of the sides of the thread, one to the other, is 55 degrees, and the tops and bottoms of the thread are rounded. Of these three threads, the sharp V or common V, as it is sometimes termed, is the easiest to produce, because Fig. 84 if the angles of the threading tool are correct the top and bottom will come correct of itself, whereas in the United States standard thread it is necessary to form the tool SCREW CUTTING TOOLS. 89 us in Fig. 85, the flat at the point requiring great care to make it of correct width. Either of these threads may, however, be originated more easily than the Fig.85. \Vhitworth or English standard thread, whose / \ rounded tops and bottoms are very difficult to / \ form correctly and exactly alike. On this account the Whitworth thread is usually cut by chasers cut from a standard hob, or master tap, the hob being revolved and the chaser pressed to it. When, however, a chaser is pro- duced, it possesses the advantage that the angles of the thread sides are more correct than is the case with single- pointed tools ground upon a grinding stone. But the common V and the United States standard thread may both be cut by chasers, and in fact the United States standard thread may be cut by a chaser having the com- mon V thread ; all that is necessary being to grind off the tops of the teeth, as in Fig. 86, because, when the chaser Fig. 86. has entered the work far enough to cut the flat at the thread bottom to the correct diameter, the flat at the thread top will be left of itself. 90 COMPLETE PRACTICAL MACHINIST. Fig. 87 represents a gauge for testing the angles of threading tools for the common V, and for the United States standard threads. It is not unusual, however, to Fig. 87. employ a short metal gauge, such as shown in Fig. 88, applying it direct to the work, which will test if the tool has been correctly set with relation to the work. But when it is known that the tool is correctly formed, and has been properly set in the lathe tool post and therefore Fig. 88. GAUGE. that the shape of the thread is correct, the thread diameter may be most correctly measured by callipers, applied as in Fig. 89, which is especially advantageous when there is at hand a correct thread to set the callipers by. SCEEW-CUTT1NO TOOLS. 91 To test the pitch of a thread, to find if its pitch is alike at various parts of the thread length, gauges such as at Fig. 89. G or G' in Fig. 90 may be employed ; the work and the Fig. 90. gauge being held up to the light, which will show very ciearly any error that may exist. 92 COMPLETE PRACTICAL MACHINIST. In cutting V threads upon either inside or outside work, great care should be taken to grind the V tool to the exact proper angle, and to also set it quite true in the lathe ; to accomplish both of which results, we have the gauge shown in Fig. 91, and sold at all tool stores. The above cuts show the various uses to which this gauge can be applied. In Fig. 1, at A, is shown the manner of gauging the SCREW-CUTTING TOOLS. 93 angle to which a lathe centre should be turned ; at B, the angle to which a screw-thread cutting tool should be ground, and at C, the correctness of the angle of a screw-thread already cut. In Fig. 2, the shaft with a screw-thread is supposed to be held on the centre of a lathe. By applying the gauge as shown at D, or E, the thread tool can be set at right angles to the shaft, and then fastened in place by the screw in tool post, thereby avoiding imperfect or leaning threads. In Fig. 3, the manner of setting the tool for cutting inside threads is illustrated. The angles used in this gauge are sixty degrees. The four divisions upon the gauge of 14, 20, 24 and 32 parts to the inch are very useful in measuring the number of threads to the inch of taps and screws. The following parts to the inch can be determined by them namely, 2, 3, 4, 5, 6, 7, 8, 10, 14, 16, 20, 24 and 32. If the tool is not ground to the correct V, or is not set true in the lathe, the result is, that the threads will bear upon each other upon one side, or a portion of one side only thus reducing the amount of wearing surface, and causing the threads to soon become a loose fit, as well as to be weaker than they should be. A V thread cut by a V tool in the lathe is not so strong as one cut by a chaser, because chasers cut a thread slightly rounded at the top and bottom ; whereas the V tool leaves a sharp corner. At the termination of the thread, it is necessary to cut a recess as deep as the thread, in order to give the chaser clearance, and prevent it from ripping into the shoulder, which would form the termination of the thread in the absence of a recess. It is a very common practice to cut this groove or recess with a V tool or graver point, instead of with a round-nosed tool, thus producing a recess having 94 COMPLETE PRACTICAL MACHINIST. a conical instead of a curved outline : the result being to very seriously impair the strength of the bolt, and cause it, under severe strains, to fracture across the section of the bottom of the groove. In a series of experiments made a few years ago, by the English government, upon targets representing ships' armor, the bolts were found to be unable to withstand the shock caused by the cannon shot striking the target ; and it being observed that the fracture nearly always occurred across the section above referred to, the clearance grooves were made with a hollow curve, which obviated the defect. To calculate the change gear wheels necessary to cut a given pitch. of thread in a lathe: The pitch of a thread is measured or denominated in two ways, first : by the number of threads there are in one inch of the length of the screw ; and, second, by the dis- tance of one thread from the next one. Thus, in Fig. 92, the thread may be expressed as one of four per inch, or as a thread, having a pitch of i inch. For tine threads the pitch is usually given in the number of threads per inch. What is called (as applied to its screw-cutting wheels) a single geared lathe is one in which the driving gear is either fastened upon and revolves with the man- SCREW-CUTTING TOOLS. 95 dril or spindle of the lathe, or else is driven by an inter- mediate gear-wheel of such a size that the driving gear, though not fast upon the lathe spindle or mandril, still makes the same number of revolutions per minute as does the mandril, while at the same time no two wheels (on such a lathe) of different diameters run side by side, making an equal number of revolutions in a given time. Thus in Fig. 93 we have the driving gear D, and intermediate wheel I, and the lead screw wheel S, the Fig. 93. arrangement constituting a simple or single geared screw cutting lathe. In such a lathe we have only to consider the driving wheel or gear and the gear upon the feed screw of the lathe, the others or intermediate wheels having no effect or influence (upon the thread to be cut) other than to make up the distance between the driving and feed screw gears, and thus to communicate the motion of the one to the other. Hence, having ascertained what sized wheel is required for the driving wheel and on the feed screw, 96 COMPLETE PRACTICAL MACHINIST. we may connect them together by any wheel or wheels that will answer irrespective of their sizes. It will be readily perceived, then, that if the driving gear and the feed screw gear contain respectively the same number of teeth, the lathe would be geared to cut a thread of the same pitch as the pitch of the thread on the feed screw of the lathe, because the feed screw would revolve at the same speed as the lathe did. Now, in exact proportion as the feed screw revolves, slower than does the lathe spindle or mandril, will the thread cut by the lathe tool be finer than that on the feed screw, and vice versa; hence we have whereby to find the wheels necessary to cut a thread of a required pitch in a single geared lathe the following rule : Put down the pitch of the lead screw, as the numerator of a fraction, and put beneath it the pitch of the thread you want to cut, and these figures will represent the re- quired number of teeth the wheels should have. For example, the pitch of a lead screw is 8 threads per inch, and we require to cut a pitch of 16. Then Pitch of lead screw 8 = number of teeth for the driving gear. Thread to be cut 16 = No. of teeth for the gear on the lead screw. Again : the pitch of a lead screw is 6, and we require to cut a thread whose pitch is 24. Then Pitch of lead screw 6 = number of teeth for driving gear. Pitch to be cut 24 = number of teeth for lead screw gear. If we have no wheels containing these respective num- bers of teeth, we multiply the fraction by any number we may choose, as by 2, 3, 4, 5 or 6. Thus 6 12 = number of teeth for driving gear. ~2 48 = number of. teeth for lead screw gear. Or 6 v o _ _!_ == nurober of teeth for driving gear. 24~ 72 = number of teeth for lead screw gear. Or 6 _ 24 = number of teeth for driving gear. 24 ' 96 T = number of teeth for lead screw gear. SCREW-CUTTING 97 Let us now suppose that we require to cut a fractional thread, as, say, the lead screw being 4 per inch, we wish to cut a pitch of 4i threads per inch, and all we have to do is to put down the lead screw pitch expressed in quarter inches and the pitch to be cut in quarter inches. Thus there are 16 quarters in 4 and 17 quarters in 4}. Hence, the fraction becomes 16 = number of teeth for driving gear. 17 = number of teeth for lead screw gear. If we have not these gears, we multiply by any number as before. Thus *6 32 == num her of teeth for driving gear. 17 ~~ 34 = number of teeth for lead screw gear. Or 16 o 48 = number of teeth for driving gear. 17 ~ 51 = number of teeth for lead screw gear. Or 16 64 = number of teeth for driving gear. 17 68 = number of teeth for lead screw gear. The term Compound or double geared, as applied to the screw-cutting gear of a lathe, means that there exists, between the gear wheel which is fastened to, and revolves with, the lathe spindle, and the feed screw, two gear wheels of different diameters and revolving side by side, at the same number of revolutions, by reason of being fixed upon the same sleeve or axis. The object of this arrangement is to make, between the speed at which the lathe mandril or spindle will run, and the speed or rev- olutions at which the feed screw will run, a greater amount of difference than is possible in a single geared lathe, and thus to be able to cut threads of a coarser pitch than could be cut in the latter. This is usually accom- plished by providing two intermediate wheels of different diameters, both being held by a feather to a sleeve re- volving upon an adjustable pin provided for the purpose. Thus Fig. 94 represents an arrangement of compounded gear, in which A is the driving gear, C and D the com- pounded pair of wheels carried on a stud in the swing frame F, and S the lead screw gear. In this arrange- 9 98 COMPLETE PRACTICAL MACHINIST. ineut, the driving gear A is fixed and cannot readily be taken off; hence it must in many cases be taken into account in finding the gears, all the changes being made in the wheels C, D and S. Sometimes, however, only the wheel upon the lead screw need be changed, since a wide range of pitch may be obtained without disturbing any other wheel. Suppose, for example, that the driving gear or gear on the latho mandril or spindle has 32 teeth, and that the compounded pair is arranged to reduce the motion one-half, and tho effect is the same as if the driving gear had 16 teeth and there was no compound gears employed. Fig. 94. To find the number of teeth in the wheel required to be placed on the feed screw, we have the following rule: Divide the pitch to be cut by the pitch of the feed screw, and the product will be the proportional number. Then multiply the number of teeth on the lathe mandril gear by the number of teeth on the smallest gear of t he com- SCREW-CUTTING. 99 pounded pair, and the product by the proportional num- ber, and divide the last product by the number of teeth in the largest wheel of the compounded pair, and the product is the number of teeth for the wheel on the feed screw. Suppose, for example, the gear on the lathe mandril contains 40 teeth running into the largest of the com- pounded gears which contains 50 teeth, and that the smnll gear of the compounded pair contains 15 teeth ; what wheel will be required for the feed screw its pitch being 2, and the thread requiring to be cut being 20? Pi;ch Pitch or Proportional required. feed screw. number. 20 -4- 2 = 10 Then Mandril Small com- Proportional Large corn- gear teeth. pound gear. number. pound gear. 40 X 15 X 10 H- 50 = 120 = the num- ber of teeth required upon the wheel for the feed screw. In the above example, however, all the necessary wheels except one are given ; and since it is often required to find the necessary sizes of two of the wheels, the following rule may be used : Divide the number of threads you wish to cut by the pitch of the feed screw, and multiply the quotient by the number of teeth on one of the driving wheels, and the product by the number of teeth on the other of the driving wheels ; then any divisor that leaves no remainder to the last product is the number of teeth for one of the wheels driven, and the quotient is the number of teeth for the other wheel driven. [In this rule the term "wheel driven" means a wheel which has motion imparted to it, while its teeth do not drive or revolve any other wheel ; hence the large wheel of the compounded pair is one of the wheels driven, while the wheel on the feed screw is the other of the wheels driven.] Example. It is required to cut 20 threads to the inch, the pitch of the feed screw being 2, one of the driving wheels contains 40 teeth and the other 15 : 100 COMPLETE PRACTICAL MACHINIST. Pitch required Pitch of Teeth in one Teeth in other to be cut. feed screw. driving wheel. driving wheel. 20 -=-2 X 40 X 15 = 6000. Then, 6000 -h 50 = 120; and hence one of the gears will require to contain 50 and the other 120 teeth ; if we have not two of such wheels, we may divide by some other number instead of 50. Thus: 6000 -=- 60 = 100; and the wheels will re- quire to have, respectively, 60 and 100 teeth. If there are no wheels on the lathe we proceed as fol- lows : Divide the pitch required by the pitch of the feed screw ; the quotient is the proportion between the revolutions of the first driving gear and the feed screw gear. Example. Required the gears to cut a pitch of 20, the feed screw pitcli being 4 ; here 20 -f- 4 = 5 ; that is to say, the feed screw must revolve five times as slowly as the first driving gear; we now find two numbers which, multiplied together, make five: as 2i X 2 = 5; hence one pair of wheels must be geared 2 1 to 1 and the other pair 2 to 1, the small wheel of each pair being used as drivers, because the thread required is finer than the feed screw. Fig. 95 represents an arrangement of compound gears Fig. 95. SCREW-CUTTISQ. 101 common in small American lathes. A is the actual driv- ing gear, B an intermediate, and C D are the compound pair. In this case the wheels A, B and C are fixed and Fig. 96. 102 COMPETE 'PRACTICAL MACHINIST. cannot be changed ; hence all we have to consider is the sizes of D, and of the lead screw gear S. Suppose, now, that the wheel D has the same number of teeth as wheel C, and we may neglect C and calculate the change gears the same as if D was on the lathe spindle, and A, B and C were not used. But in a majority of cases D will have to be changed as well as S, and then the size of C must be taken into account. In this case we proceed precisely as before, finding the proportion that must exist between the revolution of the mandril and of the lead screw, and arranging the wheels accordingly. The wheels necessary to cut a left-hand thread are obviously the same as those necessary for a right-hand one of the same pitch. The pitches of threads used in France are given in terms of the centimeter, and the method of finding the necessary change gears are as follows : An inch equals f J of a centimeter, or in other words 1 inch bears the same proportion to a centimeter as 254 does to 100, and we may take the fraction ?^J and re- duce it by any number that will divide both terms of the fraction without leaving a remainder. Thus fg - 2 = W- If then we take a pair of gears, having respectively 127 and 50 teeth, they will form a compound pair that will enable the cutting of threads in terms of the centimeter instead of in terms of the inch. It is obvious that as a centimeter is more than an inch, this compound pair must be used to reduce the revolutions of the lead screw, or arranged as in Fig. 96, the changes of wheels for any given number of threads per centimeter being made at D and at S only. TO CUT A DOUBLE THREAD. A double thread is one formed by two spiral grooves instead of one. Thus in Fig. 97 we have one spiral at A SCREW-CUTTING. 103 and another at B, the latter being carried as far as C only. The true pitch of the thread is in this case the pitch of one spiral, or twice the apparent pitch. To cut such a thread, we arrange the change wheels for the true pitch A and cut that spiral first. Then we stop the lathe and taking off the lead screw gear of the change wheels, and move the lathe so that the driving gear makes one-half revolution ; then we put the lead screw gear back and the lathe is adjusted to cut the second thread. Suppose, for example, that the wheels used are a 36 and a 72. as in Fig. 98 ; then we make a mark atS on the driving gear, and a corresponding one on the lead screw gear, and then take the lathe off the lead screw; we then count 18 teeth on the driving gear, make a mark on the eighteenth tooth and pull the lathe round so that the mark on the lead screw gear will engage with the eigh- teenth tooth on the lead screw gear. For a treble screw we would require to divide the driv- ing gear by three, thus, 36 -i- 3 = 12, and we must count 12 teeth from S and proceed as before ; for a quad- ruple thread we divide the 36 by 4 and proceed as before, and so on. 104 COMPLETE PRACTICAL MACHINIST. Fig. 98. LEAD -SCREW GEAR 72 TEETH HAND CHASING. To cut a screw by baud in the lathe we proceed as fol- lows: The work is turned up to the required size, and then on the outside of the work we employ' the V tool SCREW-CUTTING TOOLS. 105 shown in Fig. 99 ; which tool is made of a piece of steel about fV or i inch thick, and inch deep, the holding end being fitted into a handle. The point A is the cutting edge; the point B being formed so that when the tool is pressed firmly to the lathe rest face, it will not slip but will hold fast ; and the top face being given a little top rake when the tool is used upon wrought-iron or steel, whereas negative top rake is necessary for use upon brass work. The end of the work from which the thread starts should be filed smooth, and all the turning tool marks effaced before the attempt is made to start the thread, because the "lightest obstruction will cause the motion of the starting tool to be irregular, and this will prevent the chaser from Fig. 99. SIDE VIEW TOP VIEW readily picking up the thread, which is a delicate opera- tion, requiring great care, even from an experienced hand. When the thread starts from the end of the work, it is necessary to round off the corner, because (assuming the thread to be a right hand one) it is easier to start the thread at the right hand end, and carry it forward with the chaser, than it is to start it at the left hand end and carry it back to the right. Similarly for a left hand thread, it must be started at the left hand end, and carried to the right, and in this case the corner may be rounded off, either before or after chasing the thread at pleasure. To start the thread, the lathe should be run at a fast ppeed ; and the heel of the tool being pressed firmly to the 106 COMPLETE PRACTICAL MACHINIST. face of the lathe-rest, the point of the V of the tool being brought firmly into, contact with the work, while the handle of the tool must be twisted from right to left at the same time as it is moved bodily from the left to the right. It is the relative quickness with which these combined movements are performed which will determine the pitch of the thread. The results of these combined movements will be a fine groove cut upon the work, and of the same distance from one groove to the next as the distance of one tooth of the chaser to the next. If the spiral groove so cut is only the proper pitch at one part, as, say, at the starting end, the chaser may be so held and applied as only to touch that end, when it will readily find the groove if applied lightly to it. Then several light cuts may be taken off that end, before attempting to carry the thread along. The chaser is applied by being pressed lightly against the work, and moved along the lathe-rest at as nearly the proper speed as can be judged. The chaser should be held so that its hind teeth press hardest against the work, which will keep them in the starting groove and act as a guide to the front teeth, while they extend Ihe groove, carrying the thread forward to the required distance on the work. The reason for running the lathe at a comparatively fast speed is, that the tool is then less likely to be checked in its movement by a seam or hard place in the metal of the bolt, and that, even if the metal is soft and uniform in its texture, it is easier to move the tool at a regular speed than it would be if the lathe ran comparatively slowly. If the tool is moved irregularly or becomes checked in its forward movement, the thread will become "drunken/* that is, it will not move forward at a uniform speed ; and if the thread is drunken when it is started, the chaser will not only fail to rectify it, but, if the drunken part occurs in a part of the iron either harder or softer than the rest SOU K W- CUTTING. 107 of the metal, the thread will become more drunken as the chaser proceeds. It is preferable, therefore, if the thread is not started truly, to try again, and, if there is not suffi- cient metal to permit of the starting groove first struck being turned out, to make another further along the bolt. It takes much time and patience to learn to strike the requisite pitch at the first trial ; and it is therefore requi- site for a beginner to leave the end of the work larger in diameter than the required finished size, so as to have metal sufficient to turn out the first few starting grooves, should they not be true or of the correct pitch. If, how- ever, a correct starting groove is struck at the first attempt, the chaser may be applied sufficiently to cut the thread down to and along the body of the bolt; then the projec- tion may be turned down with the graver to the required size, and the chasing proceeded with. After the thread is struck, and before the chaser is ap- plied to it, the top face of the rest should be lightly filed to remove any burrs which may have been made by the heel of the V tool or graver; or such burrs, by checking the even movement of the chaser, will cause it to make the thread drunken. Where the length of the thread ter- minates, a hollow curved groove should be cut, its depth being even with the bottom of the thread ; the object of this groove is to give the chaser clearance, and to enable you to cut the thread parallel from end to end and not to leave the last thread or two larger in diameter than the rest. Another object is to prevent the front tooth of the chaser from ripping in and breaking off, as it would be very apt to do in the absence of the groove. TO MAKE A CHASER. Chasers are cut frnm a hub, that is to say, a cutter formed by cutting a thread upon a piece of round steel, and then forming cutting edges by cutting a series of grooves along the length of the hub. These grooves 108 COMPLETE PRACTICAL MACHINIST. should be V-shaped, the cutting side of the groove having its face pointing radially towards the centre of the hub. Hubs should be tempered to a brown color. A chaser is made from a piece of flat steel whose width and thickness increases with the pitch of the thread ; the following pro- portions will, however, be found correct: NUMBER OF THREADS PER INCH. NUMBER OF TEETH IN THE CHASER. THICKNESS OF THE CHASER. 24 to 20 18 to 14 12 to 8 6 to 4 12 to 14 10 9 to 6 7 to 6 i inch. 5 " 'f " The end face of the chaser should be filed level and at an angle with both the top face and the front edge of the steel, both top and bottom rounded off so that at the top it will not dig into the shoulder at the end of the thread, and at the bottom it will not strike against a burr or other obstruction or the face of the lathe rest, and thus be re- tarded in its forward movement while being cut. The hub is then driven in the lathe between the centres, the chaser being held in a handle sufficiently long to enable the operator to hold it with one hand, and press the shoulder against the end so as to force the end of the chaser against the hub, which will of itself carry the chaser along the rest. During the operation of cutting the chaser by the hub, the former will be upside down, its cutting face (when finished) being that which during this operation is resting on the face of the lathe-rest, which latter should be placed a short distance from, and not close up to the hub. After the chaser has passed once down the hub, special attention should be paid as to whether the front tooth will become a full one ; if not, the marks cut by the hub should be filed out again, and a new trial essayed. It must be borne in mind that, the chaser being held upside down, the back tooth, while cutting the chaser, becomes the front SCREW-CUTTING TOOLS. 109 one when the chaser is reversed and ready for use. The hub should be run at a comparatively slow speed, and kept freely supplied with oil, it being an expensive tool to make, and this method of using preserves it. In Fig. 100, A is a chaser whose front tooth is not a full one; B is a chaser with a full front tooth; and it is obvious that the half tooth at A would break. Fig. 100. A vvvvx 1 KAAA The cutting operation of the hub upon the chaser is continued until the thread upon the latter is cut full, when it is taken to the vise and filed as follows : The top and bottom edges immediately behind the front tooth are rounded off as already directed. Then along the bottom of the chaser the teeth are rounded off to prevent them from catching against any burr on the face of the lathe rest. An outside chaser for cutting wrought-iron by hand should be made hollow in the length of the tooth, and have top rake, to enable it to cut easily; for the strain required to bend the shaving out of the straight line will hold the teeth to their cut. Top rake may, in fact, be applied to such an extent that the chaser will cut well of itself without having any force applied to it except suffi- cient to keep it level, but if made so keen, it soon loses its edge and is very apt to break. For use on cast-iron or brass, an outside chaser must be 10 no COMPLETE PRACTICAL MACHINIST. Fig. 101 made less keen by giving the top face of the teeth no rake, or else negative top rake and cutting the teeth less hollow in their lengths. The latter object is obtained by moving the handle, in which the chaser is fixed, up and down while the hub is cutting it. The lathe rest should be so adjusted that the chaser teeth cut above the horizontal centre of the work. The teeth of the chaser should fit the thread on the bolt along all their length when the body of the chaser is horizontal, and then the least raising of the handle end of the chaser will present the teeth to the work in position to cut, while the teeth behind the cutting edge will fit the thread being cut, sufficiently close to form a guide to steady the chaser. This method of using will not only keep the thread true, but will preserve the cutting edge of the chaser. If a chaser has top rake, and the handle end is held too high and so that the back of the teeth are clear of the thread, it will cut a thread deeper than are its own teeth ; if, on the other hand, the top face is beveled off, and the handle is held too high, it will cut a thread shal- lower than the chaser teeth. Fig. 101 represents a chaser in use on wrought-iron. It will be observed that the tops of the teeth do not stand at a right angle to the side edges of the chaser; the object of this is to make the front edge of the chaser clear the driver or dog driving the work. An inside chaser, that is, one for cutting threads in a hole or bore, should be, if to be used for cutting a right- handed thread, cut off a left-handed hub, otherwise the chaser will have its thread sloping in the opposite direc- tion to the thread to be cut. This is shown as follows : SCREW-GUTTING TOOLS. Ill In Fig. 102 is shown a top view of an inside chaser applied to a piece of work represented to be cut in half so as to expose the chaser to view. Now in order to en- Fig. 102. able the cutting of the chaser from the hob it must be bent as shown in Fig. 103, in which C represents the chaser, R the lathe band rest and H the hob. 112 COMPLETE PRACTICAL MACHINIST. An end view is shown in Fig. 104, and it is seen that the chaser teeth will slant in the direction of the dotted Fig. 104. liue B B. But when we come to straighten the chaser and turn it around as we must, to apply it to the work, we shall find that the teeth slant in the wrong direction, as .SCREW-CUTTING TOOLS. 113 is shown in Fig. 105, in which the dotted line B B corresponds to the same line in Fig. 104 ; whereas the teeth should slant in the direction of the dotted line A A, in order to match the threads in the work. An inside chaser cut from a hob having a right-hand thread can be used to cut a right-hand one, but only by so tilting the teeth that only their edges have contact with the bore of the work. Now since an inside chaser would be too keen and would hence rip into the work if it pos- sessed any top rake, and since it usually requires to have a slight degree of negative top rake, tilting it causes it to cut a thread shallower than the depth of its own teeth. In the absence of a hob an inside chaser may be cut by a piece of wrought-iron having a hole and a slot cut in the side of the hole. If then the chaser is forged straight ready for use and fastened into the slot, and the hole is tapped out, the tap will at the same time cut the teeth upon the chaser, a right-hand tap cutting a right-hand chaser. In adopting this plan, however, it is proper to use a tap of a diameter large in proportion to the pitch of the thread, otherwise the teeth of the chaser will be hol- lowed too much in the direction of their length, and will in consequence jar or chatter when cutting, especially when in use upon long bores, in which cases the teeth cut at a long distance out from the lathe rest. It is a good 1 Ian to bore a quarter-inch hole in the top face of the lathe rest, and to insert therein a small pin, against which the edge of the chaser opposite to the teeth may be pressed, so that the pin will act as a fulcrum to force the teeth into their cut. Inside threads are started by pressing the teeth lightly against the bore of the work, and moving the chaser for- ward at about the requisite speed. The corner of the bore of the work should be slightly rounded off (as should also the corner on the end of work to be chased with an outside thread) to prevent the chaser teeth from catching ngainst it. 10- 114 COMPLETE PRACTICAL MACHINIST. Either an inside or an outside chaser may be employed to cut a double or even a triple thread. A double thread is one in which the distance from one thread to the next is only one-half the actual pitch of the thread. Thus sup- posing a thread of five to an inch to be started in a screw- cutting lathe, and that the tool point is then moved later- ally so as to cut another groove between the grooves first cut, there will be two threads each of a pitch of five to an inch, and yet the distance from one thread to the next will only be one-tenth of an inch, hence a chaser of the latter pitch may be used to cut up the two threads, thus producing a double thread whose actual is twice that of. its apparent pitch. Beginners should always stop the lathe and examine a single inside thread as soon as it is struck, for it is an easy matter to cut a double female thread in consequence of moving the chaser too fast, nor will the error be dis- covered until the thread is finished. Double outside or male threads, to be cut by hand, can be most easily started by the chaser, moving it twice as fast as would be required for a single thread, rounding off the corner of the bolt end, and taking care to cut princi- pally with the hindermost teeth. The proper temper for the teeth is a deep brown, or, for unusually hard metal, a straw color. For chasing wrought- iron, the lathe may be run so that the teeth will perform about 40 feet, for steel about 30 feet, for cast-iron 50 feet, and for brass about 80 feet, of cutting per minute. The quickest way to cut a number of threads upon bolts requiring to have a true thread and of an ordinarily good fit, is to take about two good cuts with a screw tool in the lathe, and then fastening a solid die in the vise to screw the bolt through the solid die by the aid of a wrench on the bolt head. The cuts taken in the lathe will make the bolt enter the die easily and true, while the die will insure Correctness of size in the thread; bolts threaded thus may SCREW- CUTTING TOOLS. 115 be screwed at least four times as quick us by finishing them entirely in the lathe. In making a hob or master-tap for use to tap solid dies, cut in it as many flutes as will leave sufficient strength to the teeth, and let the number be an odd one. To clean rusted threads ou studs in their places, or to remove burrs from them, make a steel nut and file two slots through it after the manner of a solid die ; and, after tempering it to a light straw color, screw it along the threads requiring to be cleaned, applying a little oil. It must not be forgotten, that as steel shrinks in hardening, the tap used for this purpose should be a little above the standard size, or else worked sufficiently in the nut to cut it out larger than the normal size. CHAPTER V. LATHE DOGS, CARRIERS OR DRIVERS. The simplest form of carrier or dog for lathe work is the bent-tailed dog, shown Fig. 106. i n Fig. 106, its bent end pro- jecting into a slot in the face plate. It is objectionable, how- ever, inasmuch as it is driven at the leverage A from the work it exerts a strain tending to bend it. This may be to some extent obviated by leaving its end straight and driving it with a pin projecting from the face plate, as in Fig. 107. The driv- ing strain may be further equal- ized by employing two pins, as in Fig. 108, but it is difficult to bring both the driving pins to bear upon the dog. This may, however, be accomplished by the means shown in Fig. 109, which represents a face plate with the two pins thread into nuts in a T groove provided on the face plate. The pins are screwed up moderately tight upon the work and the cut is put on. If one pin only meets the dog it will slip in the groove and cause the other pin also to drive, and both pins may then be screwed firmly home to their nuts. A more perfect method of equalizing the driving strain is by means of the Clements driver, which is self-adjus:ing (116; LATHE DOGS, CARRIERS OR DRIVERS. 117 Fig. 107. 118 COMPLETE PRACTICAL MACHINIST. and is constructed as shown in Fig. 110. The plate F has four slots as A B, and through these and the face plate pass bolts C D, on which are small sliding blocks fitting into the slots in F. The work driving pins P P arc threaded into nuts that are iw T grooves, pro- Fig. 110. vided in F. When the pins meet the work driver the plate F moves upon the face plate, giving both pins an equal degree of driving pressure. When the work requires to be driven backwards as well as forward, as in the case of screw-cutting, the dog may be secured by a set screw, such as E in Fig. 111. Fig. 111. LATHE DOGS, CARRIERS OR DRIVERS. 119 For taper threads, however, the set screw must allow the dog end to move in the slot. For driving bolts the driver may be formed as in Fig. 112 and bolted to the face plate, which saves the trouble Fig. 112. Fig. 113. of fastening the driver to each bolt. Fig. 113, which 1*3 taken from "jThe American Machinist," represents an adjustable driver of this kind. One of the jaws, it will be observed, fits into a dove-tailed slide- way, and a screw is provided whereby the width of opening between the jaws may be adjusted to suit the size of the work. Drivers of this kind are es- pecially suitable for small work, as they project less and are therefore less in the way than ordinary drivers, and may also be made thinner so as to accommodate thin bolt heads. Fig. 114 represents tlie wood turner's spur centre, the wings being straight 120 COMPLETE PRACTICAL MACHINIST. on the outside and coned within, so as to compress the wood around the central point and thus keep it true while at the same time obviating the liability to split the work. Fig. 114. A For short work the wood worker uses the screw chuck shown in Fig. 115, the work being centred and driven by the conical screw. For work that is true, the face A Fig. 115. A may be made hollow as shown, which tends to true the work. Mandrils or arbors, as the smaller sizes are usually termed, should have their centres formed as in Fig. 116, the countersink being double, or else there should be a flat recess turned about the countersink, the object being LATHE A R 110 US. 121 in botli cases to prevent the blows given to drive the man- dril into the work from bruising the centres and causing them to run out of true. Mandrils should be made Fig. 116. slightly taper, and made of wrought-irou, or what is better, hardened steel. Fig. 117 represents an adjustable arbor or mandril. Fig. 117. Fig. 118. The body A is coned and the sleeve is split, as JB shown in Fig. 118, so that by means of the nut the sleeve may be forced up the arbor and its diameter made to unscrew to fit the bore of the work. Expanding man- 122 COMPLETE PRACTICAL MACHINIST. drils are especially useful for holes that are reamed, because as the reamer wears, the size of hole it produces diminishes and will not fit a solid standard parallel arbor. Fig. 119 represents a threaded arbor for work that is tapped, and it is seen that if the hole is not tapped quite true with the face the work will cant over and the facing Fig. 119. Fig. 120. c M T will not be true with the thread axis. This may he avoided by using the arbor shown in Fig. 120, a ring being interposed between the work and the arbor shoulder. This ring has two diametrically opposite projections, A on one side and two B on the other, which balances the work and permits it to become locked true with the thread. CENTRING LATHE WORK. The centres of a lathe should both be of the same degree of cone so that the work will not wear to different o shapes when turned end for end in the lathe. The live centre should be tempered to a blue, which will preserve it, while leaving it quite soft enough to enable it to be turned up to true it with a fully hardened cutting tool. If a centre grinding device is at hand the centre may also be hardened to a straw color. Fig. 121 represents a centre grinding device for attachment to the lathe slide-rest in connection with the tool post. It con- sists simply of a countershaft above, driven from a pulley on the lathe live spindle. LATHE CENTRE GRINDING. 123 The countershaft drives an emery wheel spindle below, which has end motion through its bearings, so that it may be fed to and fro along the cone of the lathe centre. The Fig. 121. emery wheel spindle is set at such an angle that the wheel operates a rear side of the lathe centre, so that the wheel and the centre revolve in opposite directions. The quickest method of centring lathe work is by 124 COMPLETE PRACTICAL MACHINIST. means of a centring machine, such as in Fig. 122, which consists of a live spindle to drive the drill, and counter- shaft and a universal chuck to hold the work which should be freely supplied with oil during the drilling process. Fig. 123 represents a centre-drilling attachment for )athe work. In the tail spindle T is a cup or coned chuck D to hold that end of the work W true. S is a standard bolted to the lathe shears and carrying two fixed pins P CENTRING LATHE WORK. 125 which are each enveloped by a spiral spring. G is a piece having arms fitting over the pins P, and is capped or covered to receive the other end of the work. A small hole through the centre of G admits the drill. It is ob- vious that when the tail spindle T is fed up, it will feed the work to the drill, the piece G moving with the work against the pressure of the springs or pins P. Fig. 123, Fig. 124 represents a combined drill and countersink for centre drilling, the drill and countersink being in one piece. Fig. 125 represents a combined drill and counter- Fig. 124. sink, in which a small twist-drill is let into the counter- sink and secured by a small set screw S so that the drill may be moved outward as it wears shorter. When very true work is required it is preferable to so shape the countersink that the lathe centre will first bear at the smallest part of the cone as is shown in Fig. 126. This will cause the countersink to wear and keep true with the hole. If the centre drilling is to be done by hand it is very 126 COMPLETE PRACTICAL MACHINIST. important to relax every few seconds the hold upon the work sufficiently to permit it to make about a third of a Fig. 126. Fig. 127. revolution, which may be done while the other hand is supplying oil to the drill. The object and effect of this is to cause the centre drilling to be true, which otherwise it would not be, especially if the work is compara- tively heavy, or heavier on one side than on an- other. If, however, the work requires to run very true, as in the case of recen- triug work which has once been turned, the square centre must be employed to cut the centre of the worl^ true to the circumference. A square centre is a centre fitted to the lathe in the same manner as the common centre, but having four flat sides ground upon its conical point, all four sides meeting at the point, and having sharp edges as shown in Fig. 127, the flutes serving to reduce the area of surface to be ground up when sharpening the cut- ting edges. To recentre work that has already been turned, the square centre is put in the tailstock spindle of the lathe, in the same way as the ordinary centre is placed, the work having a dog or driver placed on it, as if the inten- tion were to take a cut with the work placed in the lathe between the centres. A piece of iron or steel, hav- ing a hollow or flat end (as, for instance, the butt end of ti tool) must then be fastened in the tool post of the lathe ; then the lathe may be started and the tool end wound against the end of the work (close to the square centre) CENTRING LATHE WORK. 127 until it touches it and forces it to run truly, in which position the tool end is left, while the square centre is fed up and into the work until the latter is true, when the operation will be completed. Before any turning is done to the diameter of any lathe work which runs between the centres, the ends of such work should be made true; because if there be a projecting part on the end, or if the latter is not quite true, the centre gradually moves over to the lowest side, as shown in Fig. 128, it being obvious that the countersink would move over as it wore from the side C towards the side D of the work. All work which requires to be turned at both ends (and hence must be turned or placed end for end in the lathe) should be roughed out (that is, cut down to nearly the re- ^ 1 9- 128. quired size) all over before any part of it is finished, or, when turned end for end in the lathe, the part first turned up will run out of true with the part last turned up, though the lathe centres may be correctly placed. This may be caused by the centres of the work moving a little as they come to their bearings on the lathe centres, or in conse- quence of breaking the skin of the work ; for nearly all work alters in form as its outside skin is removed, especi- ally work in cast-iron. FINISHING LATHE WORK. The process to be adopted in finishing lathe work de- pends upon the degree of polish it is required to have. Small work may be given the highest degree of polish by the use of the file and emery paper. The finishing cut should be taken with a sharp tool and as smoothly as possible, so as to have as little work as posssible for the file to do, because much filing will make the work out of 128 COMPLETE PRACTICAL MACHINIST. round. Nothing coarser than a dead smooth file should be used, the work being run at a quick speed, or say at a circumferential speed of not less than about 170 feet per minute. The file should be applied lightly to the work and with quick strokes, for if the file is held stationary, the filings will become locked in the file teeth, forming pins, which will cut scratches. To prevent this we may apply either chalk or oil to the file and clean it a for one dozen strokes or so, so as not to permit it to clog. When chalk is use.!, simply brushing the hand over the file \\ill suffice. EMERY CLOTH AND PAPER. For ordinary work the common grades of emery paper and cloth may be employed, the finest being flour emery cloth or paper. The same grade of emery will cut coarser if placed on cloth than if on paper, because the surface of the cloth is not so smooth and even as that of the paper, and the consequence is that the grains of emery which are attached to the high spots on the cloth present a keener cutting edge and surface to the work than the rest of the surface. The main advantage of emery cloth lies in that it will wear longer because it is not so apt to tear. To fit emery cloth or paper for very fine work it should be used upon the work until the entire surface becomes worn even and glazed ; the more it is worn and glazed the finer it will finish, and this remark applies equally to all kinds of emery cloth and paper, or crocus cloth. There is, how- ever, an emery paper much finer than any other, its grades ranging from 1 to 0000, and it will produce a finish so fine as to give the work a finish and appearance equal to the finest silver or nickel-plating. The method of using to produce a really fine finish is to revolve the work very fast ill the lathe and to keep the EMERY POLISHING. 129 emery paper moving rapidly, endwise of the work, so that the marks shall cross each other at a very obtuse angle. The coarser grades of cloth should be applied first, each successive grade being used until it has entirely removed the marks left by the grade previously used. The final polish is given by number 0000 paper, moved laterally Fig. 129 Fig. 130. along the work very slowly, and under a very light pres- sure. To prepare the paper for the final finishing we must take the 0000 paper, and, giving the work a coating of oil barely sufficient to dull the polish, apply the paper, continually reversing its position in the hand so that all parts will become worn, the effects of the slight oiling being to cause the particles of metal cut off the work to 130 COMPLETE PRACTICAL MACHINIST. Fig. 131. adhere to and form a glaze upon the surface of the emery paper, and all metals polish best by being rubbed with a glazed surface composed of minute particles of the same metal as themselves ; it follows, then, that the more emery paper or cloth becomes worn the finer it will polish. For larger and rougher work the filing may be done by an ordinary smooth file and suc- ceeded by a polishing clamp consisting of two pieces of soft -wood hinged by leather and containing holes to receive dif- ferent sizes of work. The work is supplied with grain emery and oil, and is run at a quick speed, the clamp being closed firmly upon it and gradually moved to and fro. Towards the last of the process no fresh emery is applied, which makes the polish more perfect. Grinding clamps for finish- ing work to gauge diameters are made as in Fig. 129, the two hinged halves being made of cast-iron recessed so as to receive a lining of babbitt metal, and held together by a screw D and pin A. In the small sizes a split bush, such as in Fig. 130, will serve. For grinding out bores an arbor, A A, Fig. 131, is em- ployed, having in it a groove C. B is a babbitt metal bush cast on its projection into the groove C serving as a driving key. As the diameter of B decreases, it may be driven further up the arbor or mandril, which, being taper, will expand with B. TWO JAWED LATHE CHUCKS. 131 132. LATUE CHUCKS. Lathe chucks may be divided into three classes, as follows : 1st. Those in which the jaws are actuated simultaneous- ly, winch are called universal chucks. 2d. Those in which the jaws are actuated separately, which are called independent chucks, and 3d. Those in which the mechanism is so devised that the jaws may be oper- ated either separately or independently at will, which are termed com hi nation chucks. Figs. 132 and 133 repre- sent the Horton two-jawed chuck, with false or slip faces which are removable, so that jaws, having grip- ping surfaces of various Chapes to suit the shape of the work, may be em- ployed. The slips are dove- tailed into the jaws and further secured by pins. Fig. 134 represents what is called a box-body chuck, which is used to hold the brass turner's work. In some of these chucks the jaws are operated simultaneously by a right and left-hand screw, while in others, each jaw has its own separate screw. In the larger sizes of chucks, there are usually either three or four jaws. In a three-jawed chuck the work will be held with equal pressure by each jaw, because the fulcrum of Fig. 133. 132 COMPLETE PRACTICAL MACHINIST. the bite of each jaw is taken off the other two jaws, while in a four-jawed chuck, two opposite jaws may take all the strain, leaving the other two free from contact with the work. It is obvious, therefore, that for rough work, or work Fig. 134. that is not cylindrical, three jaws are preferable to four, but if the work is true, then the four jaws are preferable, inasmuch as they hold the work at four points instead of at three. CHUCKS. 133 Fig. 135 represents the Sweetland Chuck, which may be used as an independent or as a universal chuck. Each of the screws lor operating the jaws is provided with 11 bevel pinion, and behind these pinions is a ring provided with teeth, and which may be caused to engage with or disengage from the pinions as follows: The width of the rack has a beveled step, the outer being thicker than the inner diameter. Between this ring or rack and the face of the chuck is placed, beneath each jaw, a cam block Fig. 135. beveled to correspond with the beveled edge of the ring step. Each cam block stem passes through radial slots in the face of the chuck, so that it may be moved towards or away from the centre of the chuck. When it is moved in, its cam-head passes into the recess or thin part of the ring- rack which then falls back out of gear with the jaw-screw pinion. But when it is moved outward the cam-head slides 12 134 COMPLETE PRACTICAL MACHINIST. (on account of the beveled edge) under the ring-rack and places it in gear with the jaw-screw pinion. Thus to change the chuck from an independent one to a universal one all that is necessary is to push outwards the bolt-head of the cam-block stems, said heads being outside the chuck. The washers beneath these heads are dished to give them elas- ticity and enable them to steady the cams without undue friction. To enable the jaws to be set true for using the chuck as a universal one, a circle is marked on the chuck face, and to this circle the edges of all the jaws must be set before operating the cams to put the rack ring in gear. Fig. 136. Fig. 136, represents a new drill chuck by the Russell Tool Co., of Boston, Mass., the object of which is to pre- vent the slipping common to small chucks. The jaws A are placed in the line of strain so as to drive rather than pull the work, and are serrated to increase the grip. The piece B moves out with the jaws to support them, and the jaws are provided with lugs E, which afford them ex- tra support. As a result of these features, the chuck will hold sufficiently firmly to permit of its being used to drive work (having a diameter equal to the full capacity of the chuck) to be turned with the lathe tools. CHUCKS. 135 Chuck dogs are detached dogs which fit into the square holes of the chuck plate or face plate, being held to the plate by a nut and washer. These dogs are movable to any part of the plate, their position being regulated to conform to the shape of the work, which renders possible their employment in cases where a dog chuck would be of no service ; such, for instance, as holding a triangular or irregular shaped piece of work. The centre line of the screw should stand exactly parallel to the face of the face plate, or tightening the screws, which in this case grip the work, will force the latter towards or away from the face of the plate, according to the direction in which the screws are out of true. The screws should have their ends turned down below the thread, and should be hard- ened as directed for bell chuck screws, since these screws may be also reversed in the dog for some kinds of work. The dog should be screwed very firmly against the face plate, so as to avoid their springing. Universal or scroll chucks, containing screws or gear wheels which are enclosed, should be occasionally very freely supplied with oil, and the chuck worked so as to move the jaws back and forth to the extreme end of their movement, so as to wash out any particles of metal or dust which may have lodged or collected in them ; for proper cleaning will reduce the natural wear to a min- imum, and prevent the internal parts from cutting, as they are otherwise apt to do. When the work is liable to spring, from the pressure of the jaws of a chuck, those jaws may be slacked back a little previous to taking the finishing cut, during whicn the work ne^d not be held so tightly. From what has been already said it will be obvious that it is of great importance that, in addition to the jaws of a chuck being well fitted to the plate, there should be a large amount of wearing surface, so as to prevent as far as possible the jaws wearing loose in their slides. CHAPTER VI. TURNING ECCENTRICS. IF an eccentric has a hub or boss on one side only of its bore (as in the case of those for engines having link motions, where it is desirable to keep the eccen cries as close together as possible in order to avoid offset either in the bodies or double eyes of the eccentric rods), the first opera- tion to be performed in turning it up is to chuck it with the hub side towards the face plate of the lathe, setting it true with its outside diameter (irrespective of the hole and hub running out of true), and to then face up the outside face. It must next be chucked so that the face already turned will be clamped against the face plate, setting the eccentric true to bore the hole out, and clamping balance weights on the face plate, opposite to the overhanging part of the eccentric. The hole, the face of the hub, the hub itself (if it is circular), and the face of the eccentric must be roughed out before any of them are finished, when the whole of them may be finished, to the requisite sizes and thicknesses. The eccentric must then be turned about and held to the chuck-plate by a plate or plates clamping the hub or boss only, the diameter of the eccen- tric being set true to the lines marked to set it by ; then the diameter of the eccentric may be turned to fit the strap, the latter having been taken apart for that purpose. The reason for turning the strap before the eccentric is turned is (as may be inferred by the above) that the strap can be fitted to the eccentric while the latter is in the lathe, whereas the eccentric cannot be got into the strap while 136 TURNING ECCENTRICS. 137 the strap is in the lathe. By this method, the outside of the eccentric will be turned true with a face that lias been turned at the same chucking at which the hole was bored ; while the eccentric will stand sufficiently far from the chuck to permit of the strap being tried on when it is necessary. And, moreover, the skin of the metal will have been removed on three out of the four faces before either of the working parts (the bore and the outside diameter) is finished; and as a consequence, the work will remain true, and not warp in consaquence of the removal of the skin. Furthermore, upon the truth of the last chucking only will the truth of the whole job depend ; and if the face plate of the lathe is a trifle out of true, the eccentric will only be out to an equal amount. It is not an un- common practice (but a very reprehensible one). to face off the plain side of the eccentric, and to then bore the hole and turn the outside diameter, with the plain face clamped in both cases to the face plate. The fallacy of this method lies in the fact that, by such a procedure, the eccentric will be, when finished, out of true to twice the amount that the face plate is out of true. The strap should have a piece of thin sheet tin placed between the joint of the two halves before it is turned out, which tin should be taken out when the turning is com- pleted, and the strap bolted together again. The size for the eccentric will then be from crown to crown of each half of the strap. The object of inserting the tin is to make each half of the eccentric bed well upon the crown, and to prevent it from bearing too hard upon the points, as all straps do if the joint is not kept a little apart during the boring pro- cess. If the eccentric is already turned, an allowance may be made for the thickness of the sheet tin between the strap joint by placing a piece of the same tin beneath one of the caliper points when gauging the eccentric to take the size for the strap. 12 138 COMPLETE PRACTICAL MACHINIST. Eccentrics having a proportionally large amount of throw upon them are sometimes difficult to hold firmly, while their outside diameters are being turned to fit the strap, because the hub which is bolted against the face plate is so far from the centre of the work that, when the tool is cutting on the side of the eccentric opposite to the hub, the force of the cut is at a considerable leverage to the plates clamping the eccentrics ; and the latter are, in consequence, very apt to move if a heavy cut is taken by the tool. Such an eccentric, however, usually has open spaces in its throw, which spaces are placed there to lighten it; the method of chucking may, under such cir- cumstances, be varied as follows : The outside diameter of the eccentric may be gripped by the dog chuck, if the dogs of the chuck project far enough out to reach it (otherwise the dogs may grip the hub of the eccentric), while the hole is bored and the plain face of the eccentric turned. The eccentric must then be reversed in the lathe, and the hub and the face on that side must be turned. Then the plain face of the eccentric must be bolted to the face plate by plates placed across the spaces which are made to lighten the eccentric, and by a plate across the face of the hub. The eccentric being set true to the lines may then be turned on its outside diameter to fit the strap ; to facilitate which fitting, thin parallel s rips may be placed between the face plate and the plain face of the eccentric at this last chucking. It will be observed that, in either, method of chucking, the outside diameter of the eccentric (that is to say, the part on which the strap fits) is turned with the face which was turned at the same chucking at which the hole was bored, clamped to the face plate. In cases where a number of eccentrics having the same size of bore and the same amount of throw are turned, there may be fitted to the face plate of the lathe a disk of sufficient diameter to fit the hole of the eccentric, said disk being fastened to the face plate at the required distance from the centre of TURNING ECCENTRICS. 153 the lathe to give the necessary amount of throw to the eccentric. The best method of fastening such a disk to the face plate is to provide it with a plain pin turned true with the disk, and let iL fit a hole (bored in the face plate to receive it) sufficiently tightly to be just able to be taken in and out by the baud, the pin being provided with a screw at the end so that it can be screwed tight, by a nut, to the Fig. 137. Fig. 138. face plate. The last chucking of the eccentric is then per- formed by placing the hole of the eccentric on the disk, which will insure the correctness of the throw without the aid of any lines on the eccentric which may be set as true as the diameter of the casting will permit, and then turned to fit the strap. A similar disk, used in the same manner, may be employed on cranks, to insure exactness in their throw. 140 COMPLETE PRACTICAL MACHINIST. TURNING CRANKS. A crauk having a plain surface on its back should have such surface planed true. The large hole should be bored Fig. 139. first, the crank being clamped with its planed surface to the chuck plate of the lathe, when the hole mny be bored CHUCKING CROSSHEADS. 141 and the face of the hub trued up. To bore the hole for the crank pin, clamp the face of the hub of the crank, which has been trued up, against the plate of the lathe (the crank pin end of the crank being as it were sus- pended) ; then bolt two plates to the chuck plate, one on each side of the crank at the end to be bored, and place th' j m so that their ends just come in contact with the crank end. TO CHUCK A CROSSHEAD. The bores of a crosshead must be at a right angle with the axes intersecting, and to accomplish this great care is necessary in marking the lines that are to be used in Fig. 140. Fig. 141. chucking it in the lathe. When the forging is true enough, it is the best plan to let the crosshead cheeks rest upon the marking-off table or plate, without any paper or other 142 COMPLETE PRACTICAL MACHINIST. packing beneath them, as shown in Fig. 137, so that th6 square may be set against these two edges in the subse- quent chuckings. If the edges are out of true, so that the work will not be true if marked out by them, they Fig. 142. should be made true. This being done, the crosshend should be laid upon a plate, as in Fig 138, and the centre line A A marked around it. The centre line B B is next to be marked at a right angle to A A, and to do this the CHUCKING CROSSHEADS. 143 Fig. 143. crosshead should be turned over oil the table, as ill Fig. 137, and squared by the edges C C of the cheeks, the line A A standing vertical. When B B is drawn, we may mark off the holes from the intersection of A A with B B, and the thickness of the cheeks from line B B, and the crosshead is ready to chuck. The first chucking should be as in Fig. 139, one cheek being laid upon and bolted to an angle plate, the cross- head being set to the dotted circle on the end face of the hub and tested with a square applied to the dotted line F in Fig. 140, and also to the centre line A in Fig. 141, so that the crosshead may be set square, as well as having the circle run true. At this chucking the hole for the piston-rod would be bored, and the hub would be faced and turned. The second chu< king would be as in Fig. 142, the faced end of the hub being bolted to the angle plate, and a square being applied to the edges C C, as in Fig. 143, while the dotted face of the circle on the face of the hub is set to run true, when the cheeks may be bored and faced inside and out, with the assurance that the work will be true and the holes at right angles to one another. COUNTERBALANCING WORK. When work is to be counterbalanced, the weight should be such as will effect the counterbalance when placed at a distance from the line of centres equal to the distance from that line of the heaviest part to be counterbalanced, and 144 COMPLETE PRACTICAL MACHINIST. when the counterbalancing is to be done on work held between the centres, for example in the case of crank shafts, it is preferable to bolt the weight to the work itself aud not to the faceplate of the lathe. In the absence of proper counterbalancing the work is apt to be turned elliptical. BORING LINKS OR LEVERS. In boring a number of lever arms or other work having holes requiring to be of precisely the same distance apart, we bore and finish one with great exactitude. Then after that one is bored, and the faces of the hub are faced off true with the hole, a pin, as shown in Fig. 144, should be made, the diameter of the part A being made to neatly fit one of the holes in the end of the arms or levers, and being made longer in length than is the length of the lever hole into which it fits. B is a washer, turned to fit easily to the diameter of A, and C is a collar, solid with A. D is a stem, turned parallel and true ; and it is a little Fig. 144. less in length than the thickness of the chuck plate upon which the arm is to be held while the holes are being bored. Upon each end a screw is provided to receive d nut. The use of this stud is as follows : Upon the chuck plate of the lathe or boring machine, and at the requisite distance from the centre, is bored a hole to receive at a close fit the plain pait D, of the stud ; and into this hole that end of the stud is fastened by means of a nut. One TURNING LEVERS. 145 end of the lever or arm (being bored to fit the part A of the stud) is placed thereon, the stud being bolted to the chuck plate while the hole at the opposite end is being bored : thus insuring that the holes are exactly the same distance apart in all the levers. The manner of chucking is shown in Fig. 145 in which A represents a portion of the chuck, B the lever or arm to be bored, C the stud, and D D the plates bolted against the chuck so that their ends contact with the stem of the work to prevent it from Fig. 145. moving sideways during the operation of boring. The use of this stud, modified in shape to suit the work, is also applied to the turning of cranks, eccentrics, and other similar work, requiring unusual exactitude in the position of a hole or holes, or of a diameter in its position relative to a hole. TURNING PISTONS AND RODS. A piston should first be bored to receive the piston rod. The next operation is to rough out the body of the piston 13 146 COMPLETE PRACTICAL MACHINIST. rod and to then fit it to the piston. The piston is then made fast to the rod, by the key, the nut, or by riveting, as the case may be, and the piston and rod should then be turned between the centres. By this means, the piston is sure to be true with the rod, which would not be the case if the piston and rod were turned separately. In turning the piston follower, that is, the disk which bolts to the piston head to retain the rings in their places, slack back the dogs or jaws of the chuck after the roughing out is complete, taking the finishing cuts with the jaws clamped as lightly as possible upon the work ; because when the jaws of a chuck are screwed upon the work with great force, they spring it out of its natural shape. PISTON RINGS. The rings of metal from which piston rings are turned should have feet cast upon one end, which feet must be faced up true by taking a cut over them. The ring should then be chucked by bolting the faced feet against the chuck plate, so that the ring shall not be sprung in chuck- ing, as it would be if it were held upon its inside or out- side diameter by the jaws of a chuck. The inside and outside diameters of the ring may then be turned to their required dimensions, and the end face may be trued up, when the piston rings may be cut off as follows: First introduce the parting tool, leaving the ring suf- ficiently wide to allow of a finishing cut after cutting the ring nearly off; introduce a side tool, shown in Fig. 36, and take a light finishing cut off the side of the ring, and then cut it off. The end face of the ring in the lathe may then be trued up by a finishing cut being taken over it, when the parting tool may be introduced and the process repeated for the next ring. Piston rings are sometimes made thick on one side and thin on the other side of the diameter, the split of the ring being afterwards cut at its thinnest part, so that, when the TURNING PISTON RINGS. 147 ring is sprung into the cylinder (which is done to make the ring fit the cylinder tight and to cause it to expand as it wears, thus compensating for the wear), its spring will be equal all over and not mainly on the part of the diameter at right angles to the split, as it otherwise would be. The process of turning such rings is to face the feet of the ring from which they are to be cut, and then turn up the outside diameter to its required size. Then move the ring on the face plate sufficiently to cause it to revolve eccentrically to the amount of the required difference between the thickest and thinnest parts of the ring, when the inside diameter should be trued out, and the rings cut off as before directed. The object of turning the inside bore after and not before the outside diameter of the ring is turned, is that, during the process of cutting off the individual piston rings, the bore of the ring will be true, so that the parting tool will not come through the ring at one side sooner than at the other; for if this were the case, the parting tool, from its liability to spring and its broad cutting surface (parallel to the diameter of its cut), would be apt to spring in, rendering the cutting off process very difficult to perform ; because if the piston ring is cut completely through on one side and not on the other, it will probably bend and spring from the pressure of the parting tool, and in most cases break off before being cut through at all parts by the tool. The inside diameter (or bore) of pic ton rings is fre- quently left rough, that is to say, not turned out at all ; but whenever this is the case, the splitting of the ring will in all probability cause one end of the ring (where it is split) to move laterally one way and the other end to move the opposite way, causing the vise hand a great deal of labor to file and scrape the sides of the ring true again. The cause of this spring is that there is a tension on the 148 COMPLETE PRACTICAL MACHINIST. inside of the ring (where it has not been bored), tending to twist it, which tendency is overcome by the strength of the ring so long as it is solid ; but when it is split, the tension releases itself by twisting the ring as stated. The tension referred to is, in all probability, caused, to a certain extent, by the unequal cooling of the ring after it is cast. Iron and brass moulders generally extract castings from the mould as soon as they are cool enough to permit of being removed, and then sprinkle the sand with water to cool and save it as much as possible. The consequence is that the part of the casting exposed to the air cools more rapidly than the part covered or partly covered by the sand, which creates a tension of the skin or outside of the casting. The same effect is produced, and to a greater extent, if water is sprinkled on one part of the casting and not on the other, or even on one part more than on another. It has already been stated that brasses contract a little, sideways, in the process of boring, and that work of cast metal alters its form from the skin of the metal being removed ; this alteration of form, in both cases, arises in the case of a piston ring from the release of the tension. It sometimes occurs that a piece of work that is finished true in all its parts may unexpectedly require a cut to be taken off an unfinished part (to allow clear- ance or for other cause), and that the removal of the rough skin throws the work out of true in its various parts, as, for instance : a saddle of a lathe being scraped to fit the lathe bed, and its slides finely scraped to a surface plate; or the rest itself being fitted and adjusted to the cross slide of the saddle. If, when the nut and screw of the cross slide are placed in position, the nut is discovered to bind against the groove (of the saddle) along which it moves (the nut being too thin to permit of any more being taken off it), there is no alternative but to plane the groove in TURNING PJSTON RINGS. 149 the saddle deeper, which operation will cause the saddle to warp, destroying its fit upon the lathe bed, and the true- ness of the V's of the cross slide, and that to such an extent as to sometimes require them to be refitted. The evil effects of this tension may be reduced to a minimum by letting the casting cool in the mould, or if they are taken from the mould while still red hot, by placing them in a heap in some convenient part of the foundry, and covering them with sand kept in that place Fig. 146. for the purpose ; and by roughing out all the parts of the work which are to be cut at one chucking before finishing any one part. Piston rings are turned larger than the bore of the cylinder which they are intended to fit, and, as before stated, sprung into the cylinder. The amount to which they are turned larger depends upon the form of split intended to be given to the ring; if it be a straight one, cut at an angle to the face of the ring, which is the form commonly employed, the diameter of the ring may be 13* 150 COMPLETE PRACTICAL MACHINIST. made in the proportion of one-quarter inch per foot larger than the bore of the cylinder, sufficient being cut out of the ring, on one side of the split, to permit the ring to spring into the diameter of the cylinder, when the ring may be placed in the cylinder and filed to fit, taking care to keep the ring true in the cylinder while revolving it to mark it. Fig. 146 represents an expanding chuck for holding piston rings or similar work. It consists of an arbor or mandril A, upon which is the body B of the chuck, whose hub is coned. C is a disk bored to fit the coned hub of B, and having four splits, one of which, Z, extends to its circumference. E is a ring to receive the pressure of nut D, and it is obvious that if the latter be screwed up upon A, then disk C will be forced up the cone, and its diameter will enlarge and grip the bore of the ring or work R. The range of an expansion chuck of this kind is obviously small, hence it is suitable mainly for special work. CHAPTER VII. HAND-TURNING. TURNING work in the lathe with a tool held or guided by hand, or, as it is commonly termed, hand-turning, is ab once one of the most delicate and instructive branches of the machinist's art, imparting a knowledge of the nature and quantity of the resistance of metals to being cut, of the qualifications of various forms of cutting tools, and of the changes made in those qualifications consequent upon the relative position or angle of the cutting edge of the tool to the work ; and this knowledge is to be obtained in no other way than by the practice of hand-turning. It is the work of an instant only to vary the relative height and angle of a hand tool to the work, converting it from a roughing to a finishing tool or even to a scraper, which operations are difficult and sometimes impracticable, if not impossible, of accomplishment with a tool held in a slide rest. The experience gained from the use of slide rest tools is imparted mainly through the medium of the eyesight, whereas in the case of a hand tool the sense of feeling becomes an active agent in imparting, at one and the same time, a knowledge of the nature of the work and the tool; so much so, indeed, that an excess in any of the requisite qualifications of a hand tool may be readily perceived from the sense of feeling, irrespective of any assistance from the eye ; and in this fact lies the chief value of the experience gained by learning to turn by hand. 151 152 COMPLETE PRACTICAL MACHINIST. For instance, there is no method known to practice whereby to ascertain how much power it requires to force a slide rest tool into its cut, or to prevent its ripping in; so that a wide variation, in the tendency of such a tool to perform its allotted duty easily and without an unnecessary expenditure of power, may exist without becoming manifest to any save the experienced workman ; whereas the amount of power required to keep the cutting edge of a hand tool to its work, to hold it steadily, or to prevent it from ripping, is communicated instantly to the understanding through the medium of the sense of feeling. Nor is this all, for even the sense of smell becomes a valuable assistant to the hand-turner. Several metals, especially wrought-iron. steel and brass, emit (when cut at a high speed) a peculiar smell, which becomes stronger with the increase in the speed at which they are cut and the comparative dul- ness of the edge of the tool employed to cut them, more especially when the cutting edge of the tool is supplied with oil during the operation of cutting. The reason that this sense of smell becomes more appreciable during the operation of hand than during that of slide rest turning, is because the face of the operator is nearer to the work, and because hand-turning is performed at a higher rate of cutting speed. If a tool for use in a slide rest is too keen for its allotted duty, the only result under ordinary circumstances is, that it will jar or chatter (that is, tremble and cut numerous indentations in the work), or that it will loose its cutting edge unnecessarily soon. But a hand tool possessing this defect will in many instances rip into the work, because the power, required to prevent the strain, placed by the cut upon the tool, from forcing the tool deeper into its cut than is intended, is too great to be sustained by the hand ; and the tool, getting beyond the manipulator's control, rips into the work, cutting a gap or groove in it, and perhaps forcing it from between the centres of the HAND- TURNING. 153 lathe. If, on the other hand, a tool is of such a form that it requires a pressure to keep it to its duty, the amount of such pressure, when the tool is held at any relative height and angle to the horizontal centre line of the work, and the variation in that amount, due to the slightest altera- tion of the shape of the tool, are readily appreciated by sensitiveness of the hand ; when they would be scarcely, if at all, perceived were the same tool, under like conditions, used in a slide rest. These considerations, together with the great advan- tage in the relative rapidity with which the form and applied position of a hand tool may be varied, render hand-turning far more instructive to a beginner than any other branch of the machinist's art. It is a common practice to centre one end of the work only, and to fasten the other end in a chuck, thus making the chuck serve as a driver, and obviating the necessity of centre-punching more than one end of the work. This method will, it is true, save a little time, but is objec- tionable for the following reasons: Chucks will run quite true while they are new, and indeed for some little time, but they do in time get out of true ; and as a result, if the work requires to be reversed in the lathe so as to be turned from end to end, the part of the work turned during the second chucking will be eccentric to that part turned during the first chucking. If one end only of the work requires to be turned, and needs be true only of itself, and irrespective of the part held in the chuck, the latter may be employed; this subject will, however, be treated hereafter. Our first operation, that is, truing the end of the work, is performed with a side tool, of which there are two kinds, both being made of three-cornered (or three-square, as it is generally termed) steel, the only point of difference being in the manner of grinding them. A worn-out saw file is an excellent thing to make a side tool of, because 154 COMPLETE PRACTICAL MACHINIST. the teeth grip the rest and prevent the tool from slipping. It is not necessary to soften the file at all, but (for either kind) merely to grind it so as to make one edge a cutting one, and not make the point too thin, by grinding the end off a trifle. If the cutting edges are smoothed by the application of an oilstone, they will give a very clean and smooth polish to the work. The rest should be set at such a height that the cutting edge of the tool is slightly above the horizontal centre of the work ; and the tool should be so held that its side face stands nearly parallel with the end face of the work, the cutting edge being held slightly inclined towards the work, which will give to the tool edge the necessary clearance. Any excess of this inclination renders the tool liable to turn out of true, and destroys its cutting edge very rapidly. ROUGHING OUT. Our work, being countersunk, is now ready to be turned down to nearly the required size all over, before any one part is made to the finished size. From what has been said in another place, the impor- tance (in work which requires to be kept very true) of roughing the work out all over before any one part is finished will be obvious, since the breaking of the skin in any one part releases the tension on that part, whatever be the temperature it is under when in operation. It is not practicable, on lathe work, to at all times rough the work out all over before finishing any part ; but in our present operation, of turning down a plain piece of iron held between the lathe centres, we are enabled to pursue that course, and we will therefore commence the roughing-out process with a graver. THE GRAVER is formed by grinding the end of a piece of square steel at an angle across the end, giving it a diamond-shaped appearance. HAND-TURNING. 155 The graver is the most useful of all hand tools used upon metals. It can be applied to either rough out or finish steel, w rough t-iron, cast-iron, brass, copper or other metal, and will turn work to almost any desired shape. Held with a heel pressed firmly against the hand rest (the point being used to cut, as shown in Fig. 147, A being the work, B the graver, and C the lathe rest), it turns very true, and cuts easily and freely. This, therefore, is the position in which the graver is held to rough out the work. Fig. 147. THE The heel of the graver, which rests upon the hand rest, should be pressed firmly to the rest, so as to serve as a fulcrum and at the same time as a pivotal point upon which it may turn to follow up the cut as it proceeds. The cutting point of the graver is held at first as much as convenient toward the dead centre, the handle in which the graver is fixed being held lightly by both hands, and slightly revolved from the right towards the left, at the same time that the handle is moved bodily from the left towards the right. By this combination of the two move- ments, if properly performed, the point of the graver will move in a line parallel to the centres of the lathe, because, while the twisting of the graver handle causes the graver point to move away from the centre of the diameter of the work, the moving of the handle bodily from 356 COMPLETE PRACTICAL MACHINIST. left to right causes the point of the graver to approach the centre of that diameter ; hence the one movement counteracts the other, producing a parallel movement, and at the same time enables the graver point to follow up the cut, using the heel as a pivotal fulcrum, and hence obviating the necessity of an inconveniently fre- quent moving of the heel of the tool along the rest. The most desirable range of these two movements will be very readily observed by the operator, because an excess in either of them destroys the efficacy of the heel of the graver as a fulcrum, and gives it less power to cut, and the operator has lesc control of the tool. The handle in which the graver is held should be suf- ficiently long to enable the operator to grasp it with both hands and thus to hold it steadily, even though the work may run very much out of true. To cut smoothly, as is required in finishing work, Fig. 148.- the graver is held as shown in Fig. 148, moving it from place to place along the work, and testing it for parallel- with the calipers. For finishing curves, however, ism HAND-TURNING. 157 the end face of the graver should be ground, curved from the heel to the point, but of less curvature than the work. Even parallel work should be finished by being filed with a smooth file while the lathe is running at a high speed. As little as possible should, however, be left for the file to do, because it cuts the softer veins of the metal more readily than the rest, and therefore makes the work out of true. For use on brass and other soft metals, the two top flat sides of the graver should be ground away so as to have a negative top rake. The strain on the tool, when cutting soft metals, is comparatively slight, so that the graver is rarely applied to such metals in the position shown iij Fig. 147. THE HEEL TOOL. In those exceptional cases in which, for want of a lathe having a slide rest, it becomes necessary to perform com- paratively heavy work in a hand lathe, the heel tool should be employed. This tool was formerly held in great repute, but has become less useful by reason of the advent and universal application of the slide rest. It is an excellent one for roughing work out, and will take a very heavy cut for a hand tool, because of the great leverage it possesses, by reason of its shape and handle, over the work. A heel tool is shown in Fig. 149, A being the tool, which is a piece of square bar steel forged at the end to form the cutting edge. The body of the square part is held (in a groove formed in the wooden handle B) by an iron strap C, which is tightened by screwing up the under handle D, which contains a nut into which the spindle of the strap js screwed as the handle D is revolved. The heel F of the tool is tapered, so that it will firmly grip the face of the lathe rest, the cutting edge E being rounded as shown in Fig. 149. The tool is held by grasping the handle B at about the point G, with the left 14 158 COMPLETE PRACTICAL MACHINIST. hand, and by holding the under handle D in the right hand, the extreme end H of the handle being placed firmly against the right shoulder of the operator. The heel F of the tool must be placed directly under the part of the work it is intended to turn, the cutting edge E of the tool being kept up to the cut by using the handle D as a lever, and the heel F of the tool as a fulcrum. Not much lateral movement must, however, be allowed to the cutting edge of the tool to make it follow the cut, as it will get completely beyond the manipulator's control and rip into the work. Until some knowledge of the use of this tool has been acquired, it is better not to forge the top of Fig. 149. IDE VIEW the cutting edge E too high from the body of the tool ; since the lower it is the easier the tool is to handle. The heel tool should, like the graver, be hardened right out; but in dipping it, allow the heel F to be a little the softer by plunging the end E into the water about half way to F; and then, after holding it in that position for about four seconds, immerse the heel F also. After again holding the tool still for about six seconds, withdraw it from the water and hold it until the water has dried off the point E ; dip the tool again, and quickly withdraw it, repeating this latter part of the operation until the tool is quite cold. The object of the transient dippings is to pre- HAND-TURNING. 159 vent the junction of the hard and soft metal from being a narrow strip of metal, in which case the tool is very liable to break at that junction. The tool should be so placed in the handle that there is only sufficient room between the cutting edge and the end of the handle to well clear the lathe rest, and should be so held that the handle stands with the end H raised slightly above a horizontal position, the necessary rake being given by the angle of the top face at E. It is only applicable to wrought-iron and steel ; but for use on those metals, especially the latter, it is a superior and valuable hand tool. For cutting out a round corner, a round-nosed tool of the same description as the V tool given for starting threads by hand, but having the cutting edge ground round instead of a V shape, is the most effective ; it will either rough out or finish, and may be used with or with- out water, but it is always preferable to use water for finishing wrought-iron and steel. This is a sample of a large class, applicable to steel and wrought-iron, the metal behind the cutting edge being ground away so as to give to the latter the keenness or rake necessary to enable it to cut freely, and the metal behind the heel being ground away to enable it to grip the rest firmly. HAND-TURNING BRASS WORK. For roughing out brass work, the best and most univer- sally applicable tool is that shown in Fig. 150, which is to Fig. 150. 10t> VIEW Ji brass work what the graver is to wrought-iron or steel. The cutting point A is round-nosed. The hand rest 160 COMPLETE PRACTICAL MACHINIST. should be set a little above the horizontal centre of the work, and need not be close up to the work, because com- paratively little power is required to cut brass and other soft metals, and therefore complete control can be had over the tool, even though its point of contact with the rest be some little distance from its cutting point, which allows a greater range of movement of the tool from a fixed point. The best method of holding and guiding is to place the forefinger of the left hand under the jaw of the hand rest, and to press the tool firmly to the face of the rest by the thumb, regulating the height so that the cut- ting is performed at or a little below the horizontal centre of the work. The tool point may thus be guided with comparative ease to turn parallel, taper, or round or hol- low curves, or any other desirable shape, except it be a square corner. Nor will it require much moving upon the face of the lathe rest, because its point of contact, being somewhat removed from the rest, gives to the tool point a comparatively wide range of movement. The exact requis- ite distance for the rest to be from the work must, in each case, be determined by the depth of the cut and the degree of hardness of the metal ; but as a general rule, it should be as distant as is compatible with a thorough control of the tool. The cutting end of this tool should be tempered to a light straw color. SCRAPERS. To finish brass work, various shaped tools, termed scrapers, are employed. The term scraper, however, applies as much to the manner in which the tool is applied to the work as to its shape, since the same tool may, without alteration, be employed either as a scraping or a cutting tool, according to the angle of the top face (that is, the face which meets the shavings or cuttings) to a line drawn from the point of contact of the tool with the work to the centre line of the work, and altogether irre- spective of the angles of the two faces of the tool whose HAND-TURNING. 161 junction forms the cutting edge. To give, then, the degree of angle necessary to a cutting tool, irrespective of the position in which it is held, is altogether valueless, as will be readily perceived. Scrapers will cut more freely if applied to the work with the edges as left by the grindstone; but if they are smoothed, after grinding, by the application of an oilstone, they will give to the work a much smoother and higher degree of finish. They should be hardened right out for use on cast-iron, and tempered to a straw color for brass work. If the scraper jars or chatters, as it will sometimes, by reason of its having an excess of angle or bottom rake, or from the cutting end being ground too thin, a piece of leather, placed between the tool and the face of the rest, will obviate the difficulty. Round or hollow curves may be finished truly and smoothly by simply scraping ; but parts that are parallel or straight upon their outer surfaces should, subsequent to the scraping, be lightly filed with a smooth file, the lathe running at a very high speed to prevent the file from cut- ting the work out of true. The file should, however, be kept clean of the cuttings by either using a file card or cleaner, or by brushing the hand back and forth on the file, and then striking the latter lightly upon a block of wood or a piece of lead, the latter operation being much the more rapid, and sufficiently effective for all save the Very finest of work. If the filings are not cleaned from the file, they are apt to get locked in the file teeth and to cut scratches in the work. To prevent this the file may be rubbed with chalk after every eight or ten strokes, and then cleaned as described. After filing the work, it may be polished with emery paper or emery cloth. The finer the paper and the more worn it is, the better and finer will be the finish it will give to the work ; for all metals polish best by being rubbed at a high speed with a thin film composed of fine particles of their own nature, as ivory is 162 COMPLETE PRACTICAL MACHINIST. best polished by ivory powder, and wood by shavings cut from itself. To facilitate obtaining the film of metal upon the emery paper, the latter may be oiled to a very slight extent, by rubbing a greasy rag over it, which will cause the particles it at first cuts to adhere to its surface. Crocus cloth is the best for highly finishing pur- poses, because it will wear longer without becoming torn. It should be pressed hard against the work, and reversed in all directions upon it, so as to wear all parts of its sur- face equally, and to distribute the metal film all over; and the work should be revolved at as high a speed as possible, while the crocus cloth, during the first part of the polishing, is kept in rapid motion upon the work back- ward and forward, so that the marks made upon the work by the emery cloth will cross and recross each other. When fine finishing is to be performed, the crocus cloth should be pressed very lightly against the work and moved laterally very slowly. Kouud or hollow corners, or side faces of flanges, of either wrought or cast-iron or brass, may be polished with grain emery and oil. applied to the work on the end of a piece of soft wood, the operation being as follows: The end of the wood to which the oil and emery is to be applied should be slightly disintegrated by being bruised with a hammer; this will permit the oil and emery to enter into and be detained in the wood instead of passing away at the sides, as it otherwise would do, thus saving a large proportionate amount of material. The wood, being bruised, will also conform itself much more readily to the shape of curves, grooves, or corners. The hand rest is then placed a short distance from the work, and the piece of wood rests upon it, using it as a fulcrum. The end of the wood should bear upon the work below the horizontal level of the centre of the latter, so that depressing the end of the wood held in the hand employs it as a lever, placing considerable pressure against the work ; and the distance HAND-TURNING. 163 of the rest from the work allows the end of the piece of wood to have a reasonable range of lateral movement, without being moved upon the face of the lathe rest. The method of using the wood is the same as that employed in using emery cloth, except that it must, during the earlier stage of its application, be kept in very continuous lateral movement, or the grain emery will lodge in any small hollow specks which may exist in the metal, and hence cut small grooves in the work. Another exception is that the finishing must be performed with only such emery as may be embedded in the wood, and without the application of any oil ; especially are these directions necessary for cast- iron or brass work. The work may then be wiped dry, and an extra polish imparted to it by the application of fine or worn and glazed emery cloth, moved slowly over its surfaces. CHAPTER VIII. DRILLING IN THE LATHE. WE have next to consider drilling tools as they are em- ployed in the lathe. For boring very small holes, as in centre-drilling, it is usual and advisable to revolve the drill and use the dead centre and its gear as a feed motion. For small lathes, a small chuck or face plate is made, it having a conical stem so as to fit into the hole into which the dead centre fits. It is obvious that, as a lathe possesses no facilities for chucking work upon the tail stock, work which requires chucking, or is too heavy to be held conveniently in the hand, can only be drilled in the lathe by being chucked and revolved, the drill remaining stationary, and fitted into the socket in the tail stock spindle, or else suspended by being held by the work at the cutting end, and by the dead centre at the other end, and prevented from revolving by the aid of a drilling rest or a wrench. If the work revolves, it must of course be set to run true ; and eince the setting involves more work than would be required to hold it upon a drilling machine table, it fol- lows that the lathe is only resorted to for drilling purposes in cases in which it is imperative to use it. These instances may be classified as follows : 1. Those in which very straight and true holes are required, and in which the point of ingress and egress may be centre-punched, in which cases (the back centre of the lathe being placed in the centre punch mark, and the point of the drill in the other) the drilling is sure to be true. 164 DRILLING IN THE LATHE. 165 2. Those in which the work being very long, can be got into the lathe in consequence of the movable tail stock, when it could not be got into the drilling machine. 3. Those in which, there being turning to be done besides the boring or drilling, the whole may be performed in the lathe. 4. Those in which the holes require to be very true, the work being chucked in the lathe. The class first mentioned refers to small and light work only, and requires no comment, save that the work should be slowly revolved on the lathe centre while the drilling is progressing, so that the work will not drill out of true in consequence of its weight. The second was referred to under the heading of the cone plate, or cone chuck, as it is sometimes termed ; and the third (which usually com- prises the fourth) we will proceed to discuss. The spindle in the tail stocks of lathes are usually pre- vented from revolving by having a narrow groove along them, into which a small lug, stationary with, and pro- jecting through, the bearing of the spindle, fits. If, there- fore, a heavy strain, tending to twist the socket (as would be the case if a drill of a comparatively large size were held by it), is placed upon it, the groove, from its compar- atively small wearing surface, soon gets worn as well as the lug, and the edge of the groove bulges^ causing the socket to bind in its guide. Tail stock spindles are not, in fact, usually designed to perform such heavy duty ; hence it is an error to assign it to them, unless, as is the case in some special lathes, the tail stock spindles, and hence their bearings, are made square to suit the spindles to carry drills for heavy duty. For ordinary drilling in the lathe the twist drill is employed, but since it is used in the drill- ing machine also, it will be considered in connection with other drilling tools, and we may therefore pass to such tools as are used more exclusively on lathe work, whether for drilling holes out of the solid metal, or for enlarging 166 COMPLETE PRACTICAL MACHINIST. holes that have been cast or forged in the work and which are used upon work that is chucked upon the face plate or in other chucking devices. HALF ROUND BITS. For drilling or boring holes very true and parallel in the lathe, the half round bit shown in Fig. 151 is unsur- passed. Fig. 151. SIDE VIEW The cutting edge A is made by backing off the end, as denoted by the space between the lower end of the tool and the dotted line B, and performing its duty along the radius, as denoted by the dotted line in the end and top views. It is only necessary to start the half round bit true, to insure its boring a hole of any depth, true, parallel, and very smooth. To start it, the face of the work should, if DRILLING IN THE LATHE. 1(V7' the centre upou which the tool has been turned, which line will form a guide for filing the top face down to make the tool of the required thickness of one-half of its diam- eter. The edge A should be perfectly square with the side or diametrical edges C C. The circumference of the turned part should have the turning marks effaced with a very smooth file, by draw-filing the work lengthwise, care being taken to remove an even quantity all over. The rake of the tool, as denoted at the dotted line B, should not be greater in proportion than is there shown. This tool should be tempered to a straw color and em- ployed at a cutting speed of about fifteen feet per minute, and fed at a coarse feed by hand. For use on parallel holes, no part should be ground save the end face; whereas, in the case of taper ones, the top face may be ground, taking a little off as will answer the purpose. It should be borne in mind that, as the steel expands (and therefore becomes larger in diameter) by the process of hardening, the necessary allowance, which is about the one-fiftieth of an inch per inch of diameter, should be made when turning it in the lathe. Tools of this descrip- tion, which have a turned part to guide them, or those which depend upon the trueness of their outline or cutting edges to make them perform their duty, and which are apt, in the process of hardening, to get out of true (for all steel alters more or less during the operation of harden- ing), may be made true after the hardening or tempering by a process to be described in our future remarks on reamers, since it applies more directly to those tools than to half round bits. Fig. 152. Fig. 152 represents a bit in which a segment A is 168 COMPLETE PRACTICAL MACHINIST. cut out to admit a cutter C, which may be adjusted to size by slips of paper put in at C. Figs. 153 and 154 represent a side and an end view of a Fig, 153. Fig. 154. Fig. 155. Cutter cutter and bar (and Fig. 155 a side view of the cutter removed from the bar), especially designed for piercing holes out of the solid, and of great depth. The cutting edges C and D form a radial line, and the latter does not extend to the centre. As a result, there is formed a slightly projecting edge to the work, which acts as a guide to keep the cutter true. The end A of the cutter fits into the bore of the bar, and the latter is provided with longitudinal grooves G H, so that water forced th rough the bore of the bar will wash the cuttings out through the grooves G H. To enlarge holes and true them out, the flat drill (Fig. 156) is employed. It' is an ordinary drill made out of flat steel, having pieces of hard wood fastened to the cutting end, A being the steel, and B B pieces of wood, held on by screws. When the drill has entered the hole far enough to make it of the diameter of the drill, the DRILLING IN THE LATHE. 169 pieces of wood enter and fit the hole, steadying the drill and tending to keep it true. It is necessary, however, to true out the hole at the outer end before inserting the drill ; for if the drill enters out of true, it will get worse as the work proceeds. The drill is fed to its duty by the back lathe centre, placed in the centre upon which the drill has been turned up. The pieces of wood should be affixed before the drill is turned up, and so trued up with the drill, which should then be lightly draw-filed on the sides; and the cutting end having the necessary rake filed upon it, should be Fig. 156. tempered to a straw color, the pieces of wood being, of course, temporarily removed. For use on conical holes, the sides must be made of the requisite cone and the cutting speed in that case reduced (in consequence of the broad cutting surface) to about 10 feet per minute. (This speed will also serve in boring conical holes with a half round bit.) Such a drill is an excellent tool for ordinary work, such as pulleys, etc., because it will perform its duty very rapidly and maintain its standard size ; and it re- quires but little skill in handling. It is more applicable, however, to cast-iron than to any other metal. After the outer end of the hole has been turned true and of the required size, to receive the drill, and when the latter is 15 170 COMPLETE PRACTICAL MACHINIST. inserted for operation, it is an excellent plan to fasten a piece of metal, such as a lathe tool, into the tool post, and adjust the rest so that the end of the tool has light contact with the drill, so as to steady it. The lathe should be started, and the tool end wound in by the screw of the rest, until, the drill being true, the tool end just touches it, and having its end bevelled so as to have contact with the drill as close to the entrance of the hole as possible, in which position it is most effective. In all cases, when a drill is used in the lathe and remains stationary while the work revolves, this steadying implement should be employed, since it operates greatly to correct any tendency of the drill to spring out of true. To hold flat drills, or those having square ends, and prevent them from revolving, a drill holder may be Fig. 157. employed, either at the front end of the drill immedi- ately behind the wood, or at the other end near the dead DRILLING IN THE LATHE. 171 centre, the shape of the holder being as shown in Fig. 157, which shows five sizes. The angle of the eye to the body of the bar being so that the slide Fig. 158. rest will stand off and not be close up to the chuck plate or the end of the work. It is well to keep the eye of the drill holder close to the entrance of the hole being drilled. REAMERS. The reamer consists of a hardened piece of steel, fluted as shown in Fig. 158, so as to produce cutting edges at the tops of the flutes. It is revolved and forced endways into the work. The reamer owes its present state of per- fection to the emery-wheel, which grinds it true after the hardening process, and the main considerations in determining its form are as follows : 1. The number of its cutting edges. 2. The spacing of the teeth. 3. The angles of the faces forming the cut- ting edges. 4. Its maintenance to standard diameter. As to the first, it is obvious that the greater the number of cutting edges the more lines of contact there are to steady it on the walls of the hole; but in any case there should be more than three teeth, for if three teeth are used, and one of them is either re- lieved of its cut, or takes an excess of cut by reason of imperfections in the roundness of the hole, the other two are similarly af- fected and the hole is thus made out of round. As to the spacing of the teeth, it is determined to a great 172 COMPLETE PRACTICAL MACHINIST. extent by the size of the reamer and the facilities that size affords for grinding the reamer. The method employed to grind a reamer is shown in Fig. 159, in which is represented a rapidly revolving emery-wheel, a reamer, and also a gauge against which the front face of each tooth is held while its top or cir- cumferential face is being sharpened. The reamer is held true to its axis, and is pushed endways beneath the revolving emery-wheel. In order that the wheel may leave the right-hand or cutting edge the highest (as it must be to enable it to cut), the centre of the emery-wheel Fig. 159. REAMER must be on the left hand of that of the reamer, and the spacing of the teeth must be such that the periphery of the emery-wheel will escape tooth B, for otherwise it would grind away its cutting edge. It is obvious, how- ever, that the less the diameter of the emery-wheel, the closer the teeth may be spaced ; but there is an objection to this, inasmuch as that the top of the tooth is naturally ground to the curvature of the wheel, as is shown in Fig. 160, in which two different-sized emery-wheels are repre- sented, operating on the same diameter of reamer. The cutting edge of A has the most clearance, and is therefore the weakest and least durable; hence it is desirable to 173 GRINDING REAMERS. employ as large a wheel as the spacing of the teeth allow, there being at least four teeth, and preferably six, on small reamers, and their number increasing with the diameter of the reamer. Fig. 160, Concerning the angles of the faces forming the cutting edges, it is found that the front faces, as A and B in Fig. Fig. 161. 161, should be a radial line, for, if given rake as at C, the tooth will spring off the centre at point E in the direction of D, and cause the reamer to cut a hole of larger diameter r>* 174 COMPLETE PRACTICAL MACHINIST. than itself, an action that is found to occur to some extent even where the front face is a radial line. As this spring augments with any increase of cut-pressure, it is obvious that if a number of holes are to be reamed to the same diameter, it is essential that the reamer take the same depth of cut in each, so that the tooth-spring may be equal for each. The clearance at the top of the teeth is obviously governed by the position of the reamer with re- lation to the wheel, and the diameter of the wheel, being less in proportion as the reamer is placed farther beneath the wheel, and the wheel diameter is increased. In some forms of reamer the teeth are formed by circular flutes, such as at H in Fig. 161, and but three flutes are used. This leaves the teeth so strong and broad at the base that the teeth are not so liable to spring; but, on the other hand, the clearance is much more difficult to produce and to grind in the resharpening; hence such reamers have not found favor in the United States. As to the maintenance of the reamer to standard diam- eter, it is a matter of great importance, for the following reasons : The great advantage of the standard reamer is to enable holes to be made and pieces to be turned to fit in them without requiring any particular piece to be fitted to some particular hole, and in order to accomplish this it is necessary that all the holes and all the pieces be exactly alike in diameter. But the cutting edges of the reamer begin to wear and the reamer diameter, therefore, to reduce from the very first hole it reams, and it is only a question of time when the holes will become too small for the turned pieces to enter or fit properly. In all pieces that are made a sliding or a working fit, as it is termed when one piece moves upon the other, there must he allowed a certain latitude of wear before the one piece must be renewed. One course is to make the reamer, when new, enough larger than the proper size, to bore the holes as muHi ADJUSTABLE REAMERS. 175 larger as this limit of wear, and to restore Fig. 162. it to size when it has worn down so that the holes fit too tightly to the pieces that fit them. But this plan has the great disad- vantage that the pieces generally require to have other cutting operations performed on them after the reaming, and to hold them for these operations it is necessary to insert in them tightly fitting plugs, or arbors, as they are termed. If, therefore, the holes are not of equal diameter, the arbor must be fitted to the holes, whereas the arbor should be to standard diameter to save the necessity of fitting, which would be almost as costly as fitting each turned piece to its own hole. It follows, therefore, that the holes and arbors should both be made to a certain standard, and the only way to do this is to so construct the reamer that it may be readily adjusted to size by moving its teeth, a reamer so con- structed being shown in Fig. 162. The stock is, it will be seen, provided with dove- tail grooves that are deepest towards the point, so, that by moving the teeth towards the shank, their diameter is increased. Fig. 163 represents an adjustable reamer for very small work. It is pierced with a tapped hole and countersunk, and is split through at the end. A small plug P is in- serted, and a screw S, and it is obvious that by screwing in the plug, and then the screw, the diameter of the reamer is enlarged. The pressure between the plug P and screw S serves to lock the latter in its adjusted posi- tion. It is obvious that the split weakens the reamer, hence it is only suitable for finishing to size. 176 COMPLETE PRACTICAL MACHINIST. SHELL REAMERS. Shell reamers, such as shown in Fig. 164, are excellent tools for sizing purposes; that is, for taking a very light cut intended merely to smooth out the hole, and insure correctness in iis bore or size. The notch fits a pin in the mandril and prevents it from slipping upon the mandril as it is otherwise very apt to do. In the adjustable reamer, shown in Fig. 165, A repre- sents the stock and D the cutter, C being a regulating washer, and D and E the tightening nut and washer. Each of the cutters B fits into a dovetail and taper Fig. 163. groove in the stock, the shallow end of the groove being at the cutting end ; so that if the regulating washer C is reduced in width, the cutters will slide forward and en- large in diameter. The washer C is thus a means of adjusting the diameter Ftg. 1 64. O f the cutters ; and when the same is once adjusted, the nut D will lock it always to that precise diameter. If, therefore, several sets of cutters of different heights are fitted to one stock, and turned up while in the stock to the requisite diameter with the washer C in its place, we have a set of standard cutters which mav always be placed in position ADJUSTABLE REAMERS. 177 and locked up by the nut D, without measurement, since their sizes cannot vary. By providing another washer, very slightly thicker than the standard, the reamer will, in the case of each set of cutters, bore a hole to a driving fit, while a washer a trifle thinner will cause the cutters to bore a hole of an easily working fit. Thus the sizes of the cutters are regulated by the washer C, and not by measurement by the workman ; they are therefore at all Fig. 165. times positive and equal. The cutters are backed off on the ends only, their tops being merely lightly draw-filed after being turned up, or they may be left one thirty- second of an inch too large, and ground ofT after harden- ing, by the grinding process already described. The cutters should be forged of the best cast-steel and tem- nered to a straw color. CHAPTER IX. BOKING BARS. THE boring bar is one of the most important tools to be found in a machine shop, because the work it has to per- form requires to be very accurately done ; and since it is a somewhat expensive tool to make, and occupies a large amount of shop room, it is necessary to make one size of boring bar answer for as many sizes of hole as possible, \vhich end can only be attained by making it thoroughly stiff and rigid. To this end a large amount of bearing and close fitting, using cast-iron as the material, are necessary, because cast-iron does not spring or deflect so easily as wrought-iron ; but the centres into which the lathe centres fit are, if of cast-iron, very liable to cut and shift their position, thus throwing the bar out of true. It is, therefore, always preferable to bore and tap the ends of such bars, and to screw in a wrought-iron plug, taking care to screw it in very tightly, so that it shall not at any time become loose. The centres should be well drilled and of a comparatively large size, so as to have surface enough to suffer little from wear, and to well sustain the weight of the bar. The end surface surrounding the centres should be turned off quite true to keep the latter from wearing away from the high side, as they would do were one side higher than the other. The smaller sizes of boring bars are usually simple par- allel mandrils, having slots running through them, into which slots or key ways the cutters are fitted, being fast- ened by means of wedges. The backs of the cutters are tapered to the same degree as is the wedge, so that the key 178 SORING BAPS. 179 will bear evenly along both the edge of the keyway and the cutter. It is obvious that, if the cutter is turned up in the bar, and is of the exact size of the hole to be bored, it will require to stand true in the bar, and will therefore be able to cut on both ends, in which case the work may be fed up to it twice as fast as though only one edge were performing duty. To facilitate setting the cutter quite true, a flat and slightly taper surface should be filed on the bar at each end of the keyway, and the cutter should have a recess filed in it to fit the diameter of the bar so filed, so that after passing the cutter through the slot, it may be pushed forward in the manner of a jib, and then locked by the wedge. Such cutters not being adjustable, their diamet- rical edges need not have any clearance or rake on them, but the cutting corners should be rounded off, and the rake put on the end face of the cutter and carried around the round corner, the advantage being that the diametrical edge of the cutter will bear lightly against the bore of the work, and prevent the bar from springing. Boring bar cutters, required to be adjustable, must not be provided with a recess, but must be left plain, so that they may be made to extend out on one side of the bar to cut any requisite size of bore; it is far preferable, however, to employ the recess and have a sufficient number of cut- ters to suit any size of hole, since, as already stated (there being in that case two cutting edges performing duty), the work may be fed up twice as fast as in the former case, in which only one cutting edge operates. This description of bar for use on small holes or bores is simply a mandril, and may be provided with several slots or keyways in its length, to facilitate facing off the ends of work which requires it. Since the work is fed to the cutter, it is obvious that the bar must be at least twice the length of the work, because the work is all on one side of the cut- ter at the commencement, and all on the other side at the conclusion of the boring operation. The excessive 3.80 COMPLETE PRACTICAL MACHINIST. length of bar, thus rendered necessary, is the principal objection to this form of boring bar, because of its liability to spring. There should always be a key way, slot, or cutter way in the exact centre of the length of the bar, so as to enable it to bore a hole as long as possible in pro- portion to the length of the boring bar, and a keyway or cutter-way at each end of the bar, for use in facing off. If, however, a boring bar is to be used for a job which does not require to be faced off at the ends, the keyway should be placed in such a position in the length of the bar as will best accommodate the work, and should then be made tapering in diameter from the keyway to the ends, a short piece at one end of the bar being made parallel to receive the driving clamp. A lug, however, by which to drive the bar, is sometimes cast on one end. This form of bar is stronger in proportion to its weight, and therefore less liable to spring from the cut or to deflect than is a parallel bar. The deflection of a bar, the length of which is exces- sive in proportion to its diameter, is sufficient to cause it to bore a hole out of straight in the direction of the length of the bore, providing that the cutter is not recessed and does not cut on both sides that is to say, when the cutter has the diametrical bearing against the diameter of the hole, they serve to steady the bar and prevent it from either springing away from the cut, or from deflecting in consequence of its own weight. The question of spring affects all boring bars ; but in those which are used verti- cally, the deflection is of course obviated. Here it may be mentioned that no machine using a boring bar should be allowed to stop while the finishing cut is being taken, for the following reasons : The friction, due to the severance of the metal being cut, causes it to heat to a slight degree, and to therefore expand to an appreciable extent; so that when the cutter makes its first revolution, it is operating upon metal at its normal tem- perature, but the heat created has expanded the bore of BORING BARS. 18i the work, and hence the cut taken by the second revolu- tion of the cutter will be slightly less in diameter. This heating and expanding process continues as the cutting proceeds, so that if (after the cutter has made any num- ber of revolutions) the bar is stopped and the cylinder or other work being bored becomes cool, when the cutter makes the next revolution it will be operating upon the bore unexpanded by the heat, and hence will cut deeper into the metal, until the metal, being reheated by the cut during the revolution, the boring proceeds upon expanded metal as before the stoppage ; thus arresting the continu- ous progress of the cutter will have caused the cutting of a groove in the bore. Boring bars, for use in bores of a large diameter, are made with a head of increased diam- eter, the body of the bar being turned along its length and provided with a slot or key groove from end to end, the sliding head is bored to fit the bar, and is provided with a keyway. Thus the head may be keyed to the bar at any part of the length of the latter. Several cutters may be provided to the head, so that the work may be fed up rapidly; in such case, however, great exactitude is required in setting them, because there is no practical method of making them with a recess to insure their even projection from the bar, since the cutters are narrow, and generally cut across the whole diametrical face, so that each grinding affects their distance from the bar, and hence the size they bore. A rude form of head may be made by simply cutting a slot or slots across it, and fastening the tool or tools therein, by means of wedges, and packing pieces, if neces- sary. The only advantage possessed by this kind of bar is that it will bore a round hole, even though the bar may run out of true, by reason of either or both of the centres being misplaced, or even though the bar itself may have become bent in its length. In addition, however, to its disadvantage as to excessive length, it possesses the further 16 182 COMPLETE PRACTICAL MACHINIST. one that, unless a line drawn from the two centres upon whicli it revolves is parallel both perpendicularly and horizontally to the lathe bed, the hole bored will be oval and not round ; or if the bar is not parallel horizontally with the shears, the hole will be widest perpendicularly, and vice versa. To remedy these defects, we have the boring bar with the feeding head, which is similar to that described, save that the work remains stationary while the cutters are fed to the work by operating the head along the bar, which is accomplished as follows: either along the keyway or groove, or else through and along the centre of the boring bar, there is provided a feeding screw, pass- ing through a nut which is attached to the sliding head. As the bar revolves upon its axis, the screw is, by means of suitable gearing, caused to revolve upon its own axis, as well as around the axis of the bar, thus winding the head along the length of the bar, and thus feeding it to the cut. If the screw runs along the centre of the bar, it is usually operated by gear wheels, the movement of the feed being continuous at all parts of the revolution ; but if the screw is contained in a groove cut in the circumference of the bar, a common star feed may be attached to the end of the bar, in which case the feed of the whole revolution is given to the sliding head during that portion only of the revo- lution in which the outer arm of the star is moved by the projecting bolt or arm which operates it. From these directions, it will be readily perceived that a bar of the lat- ter form, but having the screw in its centre, is the most preferable. Care must be taken, however, to keep these bars running quite true ; for should either centre run out of true, the hole bored will be larger in diameter at that end ; while on the o*her hand, should the bar become bent so as to run out of true in the middle of its length, the hole bored will be large in the middle if the work was chucked in the middle of the length of the bar; and otherwise it will be larger at one end. BORING BAES. 183 A very important consideration with reference to boring bars is the position which the cutters should occupy towards the head or the body of the bar. We have already been over the same ground with reference to part- ing or grooving tools for lathe work, cutting tools for planing work, and cutters for cutting out holes of a large diameter in boiler plates ; but there are so many principles involved in the shape and holding position of cutting tools, so many variations, and so many instances in which the reasons for the adoption or variation of a principle are not obvious, that it is of vital importance to specify, in the case of each tool, its precise shape and position of applica- tion, together with the reasons therefor, the field of appli- cation being so extensive that the memory can hardly be relied upon. A careful survey of all the tools thus far treated upon will disclose that, in each case wherein the cutting edge stands in advance (in the direction in which the tool is moving, or, if the work move, in the direction of the metal to be cut) of the fulcrum upon which the tool is held, the springing of the tool causes it to dig into the work, deepening the cut, and in most cases causing the tool point or cutting edge to break; while in every instance this defect has been cured (upon tools liable to spring) by so bending or placing the tool that the fulcrum upon which it was held stood in advance of the cutting edge; and these rules are so universal that it may be said that pushing a tool renders it liable to spring into the work, and pulling it or dragging it enables it to take a greater cut and to spring away from excessive duty ; and thus the latter prevents breakage and excessive spring, because, when the spring deepens the cut, it increases proportion- ally the causes of the spring, and creates a contention between the strength of the tool and the driving power of the machine, resulting in a victory for the one or the other, unless the work itself should give way, either by springing away from the tool and bending, or forcing it from the lathe centres or from the clampi which hold it. 184 COMPLETE PRACTICAL MACHINIST. For instance, in Fig. 166 is shown A, a boring bar; B B is the sliding head ; C C is the bore of the cylinder, and 1, 2, and 3 are tools in the positions shown. D D D are pro- jections in the bore of the cylinder, causing an excessive amount of duty to be placed upon the cutters, as sometimes occurs when a cut of medium depth has been started. Such a cut increases on one side of the bore of the work until, becoming excessive, it causes the bar to tremble and Fig '.166. the cutters to chatter. In such a case, tool and position No. 1 would not be relieved of any duty, though it spring to a considerable degree ; because the bar would spring in the direction denoted by the dotted line and arrow E, while the spring of the tool itself would be in the direction of the dotted line F. The tendency of the spring of the bar is to force the tool deeper into the cut instead of relieving it; while the tendency of the spring of the tool will scarcely affect the depth of the cut. Tool and position No. 2 would cause the bar to spring in the direction of the dotted line and arrow G, and the tool itself to spring in the direction of H, the spring of the bar being in a direc- BORING BARS. 185 tion to increase, and that of the tool to diminish, the cut. Tool and position No. 3 would, however, place the spring of the bar in a direction which would scarcely affect the depth of the cut, while the spring of the tool itself would be in a direction to give decided relief by springing away from its excessive duty. It must be borne in mind that even a stout bar of medium length will spring consider- ably from an ordinary roughing-out cut, though the latter Fig. 167. be of an equal depth all round the bore and from end to end of the work. Position No. 3, in Fig. 166, then is decidedly preferable for the roughiug-out cuts. In the finishing cuts, which should be very light ones, neither the bar nor the tool are so much affected by springing; but even here position No. 3 maintains its superiority, because, the tool being pulled, it operates somewhat as a scraper (though it may be as keen in shape as the other tools) and hence it cuts more smoothly. 16* 186 COMPLETE PRACTICAL MACHINIST. Fig. 167 represents a boring bar, the cutters standing to one side of the bar axis so as to carry out the principle explained with reference to figure 166. Fig. 168 represents a boring bar having three cutters, and it will be seen that if one cutter, as A, leaves its cut. the pressure of the cut on the other two will spring the bar towards A, and the whole will not be round. To obt lin the very best and most rapid result, them should be but little space between the sliding head and Fig. 168. the bore of the work ; the bar itself should be as stout as is practicable, leaving the sliding head of sufficient strength ; and if the bar revolves in journals, these should be of large diameter and with ample facilities for taking up both the diametrical and end play of the boxes, since the one steadies the bar while it is performing boring duty, and the other while it is facing off end faces, as for cylin- der cover joints. The feed of a boring bar, which is slight in comparison to its duty, will rang,? at from twenty to BORING BARS. 187 thirty revolutions to an inch of travel : while that of a stout bar, held in large and closely-fitting journals, may be about sixteen revolutions per inch of tool travel for roughing-out cuts, and four revolutions per inch of travel for finishing cuts, which may be made to leave the work very smooth indeed. The tools employed for the roughing cuts should not have a broad cutting surface, and should have a little front rake. For the finishing cuts, the same tool may be employed, the end being ground to have, for use on cast- iron, a broad, level cutting surface along the cutting edge, so that, while the front edge of the tool is cutting, the behind part will scrape and thus smooth the cut. These tools should be made of the best quality of steel, and hard- ened right out, that is to say, not tempered at all. The lip or top rake must, in case the bar should tremble during the finishing cut, be ground off, leaving the face level ; and if, from the bar being too slight for its duty, it should still either chatter or jar, it will pay best to reduce the revolutions per minute of the bar, keeping the feed as coarse as possible, which will give the best results in a given time. In cases where, frrni the excessive length and smallness of the bar, it is difficult to prevent it from springing, the cutters must be made with no lip, and but a small amount of cutting surface; and the corner A should be bevelled off as shown. Under these conditions, the tool is the least likely to chatter or to spring into the cut, especially if held in position No. 3, in Fig. 166, for a tool which would jar violently in position No. 1 would cut smoothly and well if held in position No. 3. The shape of the cutting corner of a cutter depends entirely upon the position of its clearance or rake. If the edge forming the diameter has no clearance upon it, the cutting being performed by the end edges, the cutter may be left with a square, slightly rounded, or bevelled corner; but if the cutter have clearance on its outside or diamet- 188 COMPLETE PRACTICAL MACHINIST. rical edge, as shown on the cutters in Fig. 166, the cutting corner should be bevelled or rounded off, otherwise it will jar in taking a roughing cut, and chatter in taking a moderate cut. The principle is, that bevelling off the front edge of the cutter tends greatly to counteract a dis- position to either jarring or chattering, especially as applied to brass work. The only other precaution which can be taken to pre- vent, in exceptional cases, the spring of a boring bar is to provide a bearing at each end of the work, as, for instance, by bolting to the end of the work four iron plates, the ends being hollowed to fit the bar, and being so adjusted as to barely touch it ; so that, while the bar will not be sprung by the plates, yet, if it tends to spring out of true, it will be prevented from doing so by contact with the hollow ends of the plates, which latter should have a wide bearing and be kept well lubricated. It sometimes happens that from play in the journals of the machine, or from other causes, a boring bar will jar or chatter at the commencement of a bore, and will gradually cease to do so as the cut proceeds and the cutter gets a broader bearing on the work. Especially is this liable to occur in using cutters having no clearance on the diamet- rical edge ; because, so soon as such a cutter has entered the bore for a short distance, the diametrical edge (fitting closely to the bore) acts as a guide to steady the cutter. If, however, the cutter has such clearance, the only per- ceptible reason is that the chattering ceases as soon as the cutting edge of the tool or cutter has lost its fibrous edges. The natural remedy for this would appear to be to apply the oil-stone; this, however, will either have no effect or make matters worse. It is, indeed, a far better plan to take the tool (after grinding) and rub the cutting edge into a piece of soft wood, and to apply oil to the tool during its first two or three cutting revolutions. The application of oil will often remedy a slight existing chattering of a boring bar, BORING BARS. 189 but it is an expedient to be avoided, if possible, since the diameter or "bore cut with oil will vary i'rom that cut dry, the latter being a trifle the larger. The considerations, therefore, which determine the shape of a cutter to he employed are as follows : Cutters for use on a certain and unvarying size of bore should have no clearance on the diametrical edges, the cutting being per- formed by the end edge only. Cutters intended to be adjusted to suit bores of varying diameter should have clearance on the end and on the diametrical edges. For use on brass work, the cutting corner should be rounded off, and there should be no lip given to the cutting edge. For wrought-iron the cutter should be lipped, and oil or soapy water should be supplied to it during the operation. A slight lip should be given to cutters for use on cast-iron, unless, from slightness in the bar or other causes, there is a tendency to jarring, in which case no lip or front rake should be given. SMALL BORING BARS. In boring work chucked and revolved in the lathe, such, for instance, r,s axle boxes for locomotives, the device shown in Fig. 169 is an excellent tool. A represents a . 169. cutter head, which slides along, at a close working fit, upon the bar D D, and is provided with the cutters B B B, which are fastened into slots provided in the head A, by 190 COMPLETE PRACTICAL MACHINIST. the keys shown. The bar D D has a thread cut upon part of its length, the remainder being plain, to fit the sliding head. One end is squared to receive a wrench, which, resting against the bed of the lathe, prevents the bar from revolving upon the lathe centres F F, by which the bar is held in the lathe. G G G are plain washers, provided to make up the distance between the thread and plain part of the bar, in cases where the sliding head A requires consid- erable lateral movement, there being more or fewer washers employed according to the distance along which the sliding head is required to move. The edges of these washers are chamfered off to prevent them from burring easily. To feed the cutters, the nut H is screwed up with a wrench. The cutter head A is provided in its bore with two feathers, which slide in grooves provided in the bar D D, thus preventing the head from revolving upon the bar. It is obvious that this bar will, in consequence of its rigidity, take out a much heavier cut than would be pos- sible with any boring tool, and furthermore that, there being four cutters, they can be fed up four times as fast as would be possible with a single tool or cutter. Care must, however, be exercised to so set the cutters that they will all project true radially, so that the depth of cut taken by each will be equal, or practically so ; otherwise the feeding cannot progress any faster than if one cutter only were employed. For use on bores of a standard size, the cutters may be made with a projecting feather, fitting into a groove pro- vided in the head to receive them. The cutters should be fitted to their places, and each marked to its place; so that, if the keyways should vary a little in their radius from the centre of the bar, they will nevertheless be true when in use, if always placed in the slot in which they were turned up when made. By fitting in several sets of cutters and turning them up to standard sizes, correctness in the size of bore may be at all times insured, and the feeding may be performed very fast indeed. CHAPTER X. SLOTTING MACHINE TOOLS. TOOLS for use in slotting machines are divided into two classes : those used by themselves, for holes in which there is not sufficient room to admit a tool-post or bar ; and short tools, held in a tool-post on the bar, and fastened by a set screw or screws thereon provided. Referring to the first class, it is advantageous to let the cutting edge of the tool stand below the level of the bottom of the tool steel, so that in springing or deflecting from the pressure of the cut, which it is sure to do in some degree, the tool point will enter deeper into its cut, and will not, therefore, rub against it during the back or return stroke of the tool, as it is apt to do if the tool edge is level with the bottom of the tool steel. If the tool edge is level with the middle of the tool steel, the spring or deflection, due to the strain or pressure of the cut, causes the cutting edge to spring away from the work, and, therefore, lessen the depth of the cut ; hence during the back stroke the tool, being relieved of strain, rubs against the side of the cut, aud the abrasion rapidly dulls the cutting edge. Similarly by giving the front face side rake, the tool will move slightly in the direction of the feed during the cutting stroke, and be correspondingly relieved during its return stroke. When the tool is slight and stands far out from the slide or ram of the machine, it will spring enough to make the work a straight taper ; hence key ways cut in small bores will get some of their taper from this spring. (191) COMPLETE PRACTICAL MACHINIST. For cutting out a half round groove, the tool shown in Fig. 170rfhould be employed. The outline A is made as denoted by the dotted line B in cases where, from the narrowness of the tool, it is very liable to spring from the pressure of the cut, as, say, when the thickness, at Fl 9' 170< C is less than three-eighths inch, in which case the cutting edge should be lowered to a straw color ; whereas, if thicker, the edge may be hardened right out. It is well here to note that ifc is advan- tageous that the tool should have a barely per- ceptible amount of spring, in the direction of its cut, because otherwise the edge of the tool will rub against the work during the back stroke, and thus become rapidly dulled. Whenever the nature of the work to be done will admit, a holding bar and short tool, such as shown in Fig. 171 may be used. By using such a bar, short tools, such as have been already described for use in the lathe or planer, may be employed, their shortness rendering their grinding and forging much easier of accomplishment. Many of these holding bars have small pivoted boxes, similar to that shown in Fig. 171, provided to receive the tool. A is a sectional view of the bar, B is the box, pivoted at C, D is the tool, and E the set screw for holding the same. It will be observed that the set screw E screws into the pivoted box, and not into the end of the bar, and that the LJ SLOTTING TOOLS. 193 hole, provided in the end of the- bar 'to admit the set screw, is large enough to permit the set screw to have plenty of play or movement. The object of this and simi- larly designed devices is to allow the tool to move, in the direction of D, off the pivot C, and thus to prevent the tool edge from rubbing against the sides of its cut during the up stroke of the bar, the spiral spring shown being made sufficiently strong to support the box B in the position shown, but not sufficiently strong to resist much force exerted upon the tool and in the direction of D. For small or even medium sized work these devices are Fig. 171. ^- \ very efficient ; but for large, heavy, outside work, the ban themselves are too slight, and it is usual to employ a similar device (on a large scale) provided in the tool end of the slide itself. Under these conditions the slotting machine will perform as heavy duty as either the lathe or planing machine. The writer has in his possession a cut- ting taken off the outside of a crank at the Morgan Iron Works, which cutting was taken at a cut 2| inches deep, and is a full | of an inch in thickness, the tool employed being 17 194 COMPLETE PRACTICAL MACHINIST. a knife tool, ground as shown in Fig. 172. B represents the tool end of the slide of the slotting machine, A the knife tool, C the work, and from D to JE the depth of the cut. The face of the tool is ground off at an angle, in the direction of I, so that the point of the tool shall not break off when it strikes the work, and so that the strain upon the tool and working parts of the machine shall not come upon them too suddenly, and cause them to break, as would be the case were the cutting edge of the tool te strike the cut along its whole length simultaneously. As Fig. 172. shown in the engraving, the tool would strike the work at F on the edge only, which would for an instant of time exert only enough resistance to bring all the working parts of the machine to a bearing; and as the tool de- scended, the strain would gradually increase until the point of the tool reached the work. When the tool is near the end of the stroke, and therefore leaves the cut, it will do so at F first, thus leaving the cut gradually, and greatly modifying the jump due to the recoil of the working parts of the machine when relieved of the heavy strain necessary to drive such a deep and thick cut. The enormous strain SLOTTING TOOLS. 195 placed upon the tool would inevitably break it were it left very hard ; it is therefore tempered to a purple. No other tool can well be used for taking such heavy cuts, because grinding off the face, F, of any other tool would not leave the tool edge sufficiently keen to sever the metal without an excessive amount of driving power; and further, because the breadth of the face F, which sustains the force necessary to bend the cutting, is narrower in the kiiife tool than in any other, and therefore bends the cut- ting less, experiencing a corresponding decrease of strain. Cuts of such great depth and thickness cannot be well taken in slotting machines whose slides are operated by a connecting rod or link, because the excessive strain would be apt to force the connecting rod along the slot provided to alter the stroke of the machine; the eliding head is therefore provided with a strong rack on each side, oper- ated by pinions, with suitable reversing gearing attached for varying the stroke. When operating the feed of a slotting machine by hand, the work should be fed to the cut while the tool is revers- ing its motion at the top of the stroke, and not while the tool is cutting or at the bottom of the stroke, because, in either of the latter cases, the tool edge would grind against the sides of the cut during the up stroke, which would soon impair the cutting qualifications of the tool. Tool-holding bars of sizes below about 1| inches in thickness should be made of steel so as to be strong enough to resist the tendency to spring. For sizes above that they may be made of wrought-irou. CHAPTER XI. TWIST DRILLS. TWMST drills are not, as is usually supposed, of the same diameter from end to end of the twist, but are slightly taper, diminishing towards the shank end. The taper is usually, however, so slight as to be of little consequence in actual prac- tice. Neither are twist drills round, the diameter being eased away from a short distance behind the advance or cutting edge of the flute, backward to the next flute, so as to reduce the friction of the sides of the drill upon the hole and give the sides of the drill as much clearance as possible. The advance edges of the flutes are left of a full circle, which maintains the diameter of the drill and steadies it in the hole. If, from excessive duty, that part left a full circle should wear away at the cutting end of the drill, leaving the corner of the drill rounded, the drill must be ground sufficiently to cut away entirely the worn part, otherwise it will totally impair the value of the drill, causing it to ; grind against the metal, and no amount of pres- sure will cause it to cut. The advantage over other drills possessed by the twist drill is that the cuttings can find free egress, which effects a gre^it saving of time, for plain drills have to be frequently withdrawn from the 'hole to extract the cuttings, which would jamb between the sides of the hole and the sides of the drill, and the pressure will frequently become so great as to cwist or break the shank of the drill, especially in small 196 TWIST DRILLS. 197 holes. In point of fact, the advent of twist drills has rendered the employment of the flat drill for use in small holes (that is to say, from t inch downwards) totally inexcusable, except it be for metal so hard as to require a drill tempered to suit the work. Other advantages of the twist drill are, that it always runs true, requires no reforging or tempering, and, by reason of its shape, fits closely to the hole, and hence drills a straight and parallel hole, providing it is ground true. The cutting edges are usualTy ground to an angle of 60 degrees to the centre line of the drill, as shown in Fig. 177, but will be found to work more satisfactorily if ground to an angle of 50 degrees when used on brass work. The line shown along the centre of the flutes, in Fig. 173, is to serve as a guide in grinding the point central when the drill is ground by hand, but more duty and more accurate work may be ob- tained if the drill is ground in a twist drill grinding machine, so that the cutting edges may be ground true, and both cutting edges may perform equal duty. In Fig. 174 is shown a twist drill, having an edge e ground longer than the other, and the effect of this is that if the drill feed is T -J 222 COMPLETE PRACTICAL MACHINIST. to English tool steel, the former requiring to be heated to a much higher temperature for forging, and to a less tem- perature for hardening, than the latter. \^ . TOOL HARDENING AND TEMPERING. Steel is said to be hardened when it is as hard as it is practicable to make it, and to be tempered when, after having been hardened, it is subjected to a less degree of heat, which partly but not altogether destroys or removes the hardness. The degree to which this tempering is per- formed, or in other words the degree of the temper, is made perceptible and estimated as follows : By heating a piece of steel to a red heat (not so hot as to cause it to scale), and then plunging it into cold water and allowing it to remain there until it is cold, it will be hardened right out, as it is termed, that is, it will be made hard to the greatest practicable degree. If it is then slowly reheated, its outer surface will, as the temperature increases, assume various shades of color, commencing with a very light straw color, which deepens successively to a deep yellow, red, brown, purple, blue, and green, which latter fades away as the steel becomes heated to redness again, when the effects of the first hardening will have been entirely removed. It becomes apparent, then, that the colors which appear upon the surface of the steel denote the degree to which the tem- pering or resoftening operation has taken place. Having then by practice ascertained the color which denotes the particular degree of hardness requisite for any specified tool, we are enabled to always temper it to that degree, sufficiently near for all practical purposes. It is un- doubtedly true that, if the conditions of tempering which will be laid down in all our instructions are (for want of sufficient experience in the operator) varied, the colors will not present, to positive exactitude, the precise degree of temper : the difference being that, if the color forms very rapidly, the tool may be left of a lighter color; and that if TOOL TEMPERING. 223 the colors form very slowly, the tool may be left of a slightly deeper hue. The difference in temper, however, as compared to the color, will in no case be sufficient to be perceptible in ordinary tool practice, and need not, save under circumstances requiring great minuteness in the degree of temper, be paid any attention to. When a tool such as a drill requires to be tempered at and near the cutting edge only, and it is desirable to leave the other part or parts soft, the tempering is performed by heating the steel for some little distance back from the cutting edge, and then immersing the cutting edge and about one-half of the rest of the steel, which is heated to as high a degree as a red heat, in the water until it is cold ; then withdraw the tool and brighten the surface which has been immersed by rubbing it with a piece of soft stone (such as a piece of a worn-out grindstone) or a piece of coarse emery cloth, the object of brightening the surface being to cause the colors to show themselves distinctly. The instant this operation has been performed the bright- ened surface should be lightly brushed by switching the finger rapidly over it ; for unless this is done, the colors appearing will be false colors, as will be found by neglect- ing this latter operation, in which case the steel after quenching will be of one color ; and if then wiped, will appear of a different hue. A piece of w-aste or other material may of course be used in place of the hand. The heat of that part of the tool which has not been immersed will become imparted to that part which was hardened, and, by the deepening of the colors, denote the point of time at which it is necessary to again immerse the tool and quench it altogether cold. The operation of the first dipping requires some little judgment and care ; for if the tool is dipped a certain dis- tance and held in that position without being moved till the end dipped is cold, and the tempering process is pro- ceeded with, the colors from yellow to green will appear in 224 COMPLETE PRACTICAL MACHINIST. a narrow band, and it will be impossible to directly per- ceive when the cutting edge is at the exact shade of color required ; then again, the breadth of metal of any one degree of color will be so small that once grinding the tool will remove it and give us a cutting edge having a different degree of temper or of hardness. The first dipping should be performed thus : Lower the tool vertically into the water to about one-third of the distance to which it is red hot, hold it still for about sufficient time to cool the end immersed, then suddenly plunge it another third of the distance to which it is heated red, and withdraw it before it has had time to become more than half cooled. By this means the body of metal between the cutting edge and the part behind, which is still red hot, will be sufficiently long to cause the variation in the temperature of the tool end to be extended in a broad band, so that the band of yellow will extend some little distance before it deepens into a red ; hence it will be easy to ascertain when the precise degree of color and of temper is obtained, when the tool may be entirely quenched. A further advantage to the credit of this plan of dipping is that the required degree of hardness will vary but very little in consequence of grinding the tool ; and if the operation is carefully per- formed, the tool can b-3 so tempered that, by the time the tool has lost the required degree of temper from being ground back, it will also require reforging or reforming. As a rula a tool should be made to a red heat to a distance about twice the diameter of the tool steel of which it is made. The degree to which a tool may be hardened is dependent in a great measure upon its shape. The only reason for tempering any lathe tool is to stre-ngthen it, for steel har- dened right out is comparatively weak and gains strength by being tempered. The lower the temper the greater the strength. A straw color is well adapted to ordinary light tools, but very slight tools, such as say a parting tool ^ TOOL TEMPERING. 225 inch wide, may be lowered to a deep brown or almost to a purple. Stout tools, such as are shown in Fig. 2, may be made as hard as fire and water will make them ; so also may the tools presented in Figs. 8, 9, 18, 19, 28, and 34 ; while slight tools, such as are given in Figs. 29 and 30, should be lowered in temper to a light straw color. The practice of lowering stout tools to a straw color is sometimes resorted to, but it is certainly an error, for it is undoubtedly advantageous to make the tool as hard as it can be made, so long as it will bear the strain of the cut, which is possible and easy of accomplishment with Jes- sop's, Moss', Sanderson's, or other similar grades of tool steel. If a tool so hardened is found to break, it is in conse- quence either of its being bad steel or else it has been heated to too great a temperature in the process of forging or hardening, unless it has been given too much rake for the duty to which it has been allotted. Tool steel may be forged at such a temperature that it is not positively burned, and yet has lost part of its virtue ; and while under such circumstances it would break if hardened right out, it will cut and stand moderately well if the temper be lowered to a straw color. This is simply sacrificing the degree of hardness to cover the blunder committed by overheating, and it is from such causes that the variation of cutting speed employed by mechanics arises ; for a youth who has learned his trade in a shop where the tools were overheated, and consequently underhardened, settles down to the rate of cutting speed attainable under those circumstances and adheres to it; while he who has been accustomed to the use of tools prop- erly forged and hardened right out, upon entering another shop where the tools are overheated in forging and under- hardened to compensate for it, finding he cannot get the cutting speed up to his customary rate, breaks off* the tool point to see if it has been burned, and, finding that the 226 COMPLETE PRACTICAL MACHINIST. grain of the metal does not appear granulated, sparkling, and coarse, as it would do if positively burned, condemns the quality of the steel. The grain of properly forged and hardened tool steel appears, when fractured, close and fine, and of a dull, whitish tint, the fracture being even on its surface. American chrome tool steel may be made unusually hard by using very clean w r ater and adding a piece of fuller's earth and a piece of common soda, each of the size of a hazel nut, to a pailful of water. In all cases where a tool can be ground to sharpen it, it should be hardened before grinding, for steel hardened with the forged skin on is stronger and better than that in which the skin is removed before hardening. When it is intended to harden a tool right out, heat it to a cherry red to the distance that it is necessary to harden it, and plunge it into the water suddenly to the distance it requires hardening ; hold it still a moment, then dip it a little deeper, and with- draw it again to the amount of the last dipping, repeating this latter operation until the tool is cold ; for by this means the junction of the hard and soft steel in the tool is gradu- ated and not sharply defined, the result being that the tool is less liable to fracture either in hardening or in using. If the tool to be hardened has a thick part to it, let that part enter the water first and immerse the tool slowly, so that it will be cooled as nearly equally as possible and thus be prevented from cracking in hardening. Tools heated by charcoal are much superior to those heated by common coal, and need not be made quite so hot to harden. To harden steel, never get it hot enough to cause it to scale. Thin pieces of steel, and taps, dies, reamers, drifts, and similarly shaped tools, should be dip] KM! endways ; for if dipped otherwise, they are sure to warp in hardening. Very slight tools may be prevented from crack- ing by making the water quite warm before immcirin^ them, and then holding them still in the water ; in fact, all HARDENING SPRINGS. 22" water for hardening purposes should have the chill off it by heating, before being used, or the articles hardened in it are very liable to crack. If the article requires to be hardened all over, immerse it (suspended on a wire hook) so that the water may have free and equal access to the whole surface of the steel, which is not possible with tongs in consequence of their jaws covering part of the steel. HARDENING. All work to be hardened should be heated according to its shape, the work being so manipulated in the fire that the thin parts do not get to the required heat before the thick parts do. Then in quenching them in the water the thick parts should be immersed first, and the operation be performed slowly. The work should be lowered perpen- dicularly in the water and immersed deeply, and not under any circumstances moved sideways. Uneven heating warps the work in the fire, careless dipping warps and cracks it in the hardening. Always use water that is at least luke- warm, and if the article has one part much thinner than another, or is very slight, and hence liable to warp or crack, make the water a:3 hot as the hand will bear it, and dip the work edgeways, the heaviest side being downwards. Very small articles to be hardened in quantities may be heated in a piece of wrought-iron pipe, having one end closed, the pipe being revolved in the fire during the heat- ing process to equalize the heating of the work. TO HARDEN SPRINGS. Small springs, which should be made of spring-steel or double-shear steel, may be hardened as follows: Heat them to a bright cherry-red, and quench them in water having the cold chill taken off it. If, on being taken from the water, they are white, or mottled with white and a light gray, they are hard enough, but if they are dark- colored, they are not hard enough, and must be rchard- 228 COMPLETE PRACTICAL MACHINIST. erred. After 'being hardened, they may be tempered as follows : String them, if possible, on a wire, and fry them over the fire in a pan or tray containing enough lard oil to well cover them, -and heat the oil until it will blaze all over the surface, then turn the springs over and over in the blazing oil, letting them blaze long enough to be sure that the thick parts of the spring are equally heated with the thin parts. If a single spring requires tempering, it may be tempered by fastening it to a wire, and just above it put a small roll of wire to retain the oil. Heat the spring over a very slow fire, and apply oil, letting it run down the wire to the spring. Keep the spring supplied with oil, and let it blaze a minute or so. If it has a light or thin part to it, pour cold oil on that part of it during the early part of the blazing process. Large springs are first hardened, and then blazed off in whale oil, containing 2 Ibs. of tallow and \ Ib. of beeswax (or, instead of the latter, \ Ib. of black resin) to every gallon of whale oil. If a spring is made of cast-steel it must, after blazing off, be left to cool of itself without being quenched off. Springs that have the forged skin on are stronger and more elastic than those which are brightened, and all springs are reduced in elasticity by grinding off the sur- face after they are tempered ; especially, however, is this the case with those having the forged or rolled skin on. To harden machine-steel, or make cast-steel very hard, put a pound of salt to a gallon of rain-water. The longer water or a tempering liquid is used the better it becomes, but either of them are wholly spoiled if any greasy substance gets in them. All steel, as well as iron, swells by hardening, so that holes become smaller, and outside surfaces larger, in conse- quence of hardening, and this fact is often taken advantage of to refit iron or steel work that has become worn. For instance, suppose a bolt has worn loose : the bolt may be CASE HARDENING. 229 hardened by the common prussiate of potash process, which will cause it to increase in size, both in length and diam- eter. The hole may be also hardened in the same way, which will decrease its diameter ; and if the decrease is more than necessary, the hole may be ground or "lapped" out by means of a lap. Only about g V of an inch of shrinkage can be obtained on a hole and bolt by harden- ing, which, however, is highly advantageous when it is suf- ficient, because both the hole and the bolt will wear longer for being hardened. CASE-HARDENING WROUGHT-IRON. Iron may be case-hardened, that is, the surface converted into steel and hardened, as follows : First, by the common prussiate of potash process, which is as follows : Crush the potash to a powder, being careful that there are no lumps left in it, then heat the iron as hot as possible without caus- ing it to scale ; and with a piece of rod iron, spoon-shaped at the end, apply the prussiate of potash to the surface of the iron, rub it with the spoon end of the rod uatil it fuses and runs all over the article, which must then be placed in the fire again and slightly reheated, and then plunged into water, observing the rules given for immersing steel so as not to warp the article. = Another method is to place the pieces to be hardened in an iron box, made air-tight by having all its seams covered well with fire clay, filling the box in with bone dust closely packed around the articles, or (what is better) with leather and hoofs cut into pieces about an inch in size, adding thin layers of salt in the proportion of about 4 Ibs. salt to 20 Ibs. of leather and 15 Ibs. of hoofs. In packing the articles in the box, be careful to so place them that when the hoofs, leather, etc., are burned away, and the pieces of iron in the box receive the weight of those above -them, they will not be likely to bend from the pressure. When the articles are packed and the box ready to be closed with the lid, pour 20 230 COMPLETE PRACTICAL MACHINIST. into it one gallon of urine to the above quantities of leather, etc. ; then fasten down the lid and seal the seams outside well with clay. The box is then placed in a furnace and allowed to remain there for about 12 hours, when the arti- cles are taken out and quickly immersed in water, care being taken to put them in the water endways to avoid warping them. Articles to be case-hardened in tha above manner should have pieces of sheet-iron fitted in them in all parts where they are required to fit well and are difficult to bend when cold, and the heaviest pieces of work should be put at the bottom of the box. THE WEAR OF METAL SURFACES. The wear of metal surfaces, such as cast-iron, wrought- iron, steel, and brass, is governed as much by the conditions under which that wear takes place as it is by the degree of hardness of the metal. It is a general rule, that motion in one continuous direc- tion causes more wear, under equal conditions, than does a reciprocating motion, and also that the harder the metal the less the wear. To this latter rule there are, however, exceptions in favor of cast-iron, which will wear better when surrounded by steam than will any other metal. Thus, for instance, experience has demonstrated that piston-rings of cast-iron will wear smoother, better, and equally as long as those of steel, and longer than those of either wrought-iron or brass, whether the cylinder in which it works be com- posed of brass, steel, wrought-iron, or cast-iron the latter being the more noteworthy, since two surfaces of the same metal do not, as a rule, wear or work well together. So also slide-valves of brass are not found to wear so long or so smoothly as those of cast-iron, let the metal of which the seating is composed be whatever it may ; while, on the other hand, a cast-iron slide-valve will wear longer of itself, and cause less wear to its scat, if the latter is of cast-iron, than THE WEAR OF METAL SURFACES. 231 if of steel, wrought-iron, or brass. The duty in each of these cases is light ; the pressure on the cast-iron, in the first in- stance cited, probably never exceeding a pressure of ten pounds per inch, while, in the latter case, two hundred pounds per square inch of area is probably the extreme limit under which slide-valves work ; and what the result under much heavier pressures would be is entirely proble- matical. Cast-iron in bearings or boxes is found to work exceed- ingly smoothly and well under light duty, provided the lubrication is perfect and the surfaces can be kept practi- cally free from grit and dust. The reason of this is, that cast-iron, especially that of American manufacture, forms a hard surface-skin, when rubbed under a light pressure, and so long as the pressure is not sufficient to abrade this hard skin, it will wear bright and very smooth, becoming so hard that a scraper made as hard as fire and water will make it will scarcely cut the skin referred to. Thus, in making cast-iron and wrought-irou surface-plates or plauometer.-", we may rub two such plates of cast-iron together under moderate pressure for an indefinite length of time, and tho tops of the scraper-marks will become bright and smooth, but will not wear off; while if we rub one of cast-iron and one of wrought-iron, or two of wrought-iron, well together, the wrought-iron surfaces will abrade so that the protruding scraper-marks will entirely disappear, while the slight amount of lubrication placed between such surfaces to pre- vent them from cutting will become, in consequence of the presence of the wrought-iron, thick and of a dark-blue color, and will cling to the surfaces, so that after a time it becomes difficult to move the one surface upon the other. If, however, the surfaces are pressed together sufficiently to abrade the hard skin from the cast-iron, a rapid cutting immediately takes place, which is very difficult to remove, the only remedy being to entirely remove the particles of metal due to the abrasion, and lubricate very freely. 232 COMPLETE PRACTICAL MACHINIST. Under a light duty, cast-iron, especially when working under steam pressure, will wear longer and better than brass, wrought-iron or steel, even if the motion be continu- ously in one direction ; thus, for revolving side-surfaces, such as discs, it retains its superiority over the harder metals, and there is no test so great as is involved under such conditions, for the following reasons : Suppose we have a piston revolving in a cylinder. The metal on the piston, at a distance of 2 inches from its cen- tre, will pass over a circle, in the cylinder, of 12,566 inches in circumference. The metal on the piston, however, at a distance of 4 inches from its centre, will pass over a circle or surface of a circumference of 25,132 inches. Thus, we find the one part of the piston to pass over twice as much metal as does the other in performing a revolution, making the wear on that account twice as great at the large radius as it is at the small one. But this is not all, for the metal at the large radius travelled over its wearing surface, that is to say, the surface it bears against, in making a revolu- tion, at a speed twice as great as did the metal at the small one over its wearing surface, since one travelled over six- teen inches in the same time that the other travelled over eight inches of surface ; this increase further doubles the wear at the large radius, making its wear fourfold that at the small one, and giving us the rule that the wear of a revolving disc increases (as does its area) in the ratio of the square of its diameter. The result of this inequality of wear was demonstrated in the early days of locomotive- engineering, at which time the throttle-valves were in nearly all engines semi-revolving discs, with radial open- ings, the wearing surfaces being on the side face, and the disc revolving reciprocally on a centre-pin. The result of the wear on such valves was found to be very unsatisfactory, because the metal at and near the extreme circumference would wear very rapidly away. The pressure of the steam, however, by springing the outer REVOLVING SURFACES. 233 surface of the disc to its seat, would prevent the faces from leaking, but the pressure of the outer diametrical surface to its seat would be diminished in proportion to the resistance of the metal to the spring referred to, and, as a consequence, the surface of the metal at and near the centre of the disc would have upon its bearing surface not only the pressure due to the steam acting upon its exposed surface, but an amount in excess equal to that to which the outer diameter was relieved in consequence of its resistance to spring. These conditions would continue until the wear of the larger diameter becoming greater, and the amount of spring required to keep it to its seat increasing in proportion, the resistance of the metal to so much spring partly relieves the pressure of the larger diameter to its seat, and since the pressure due to the force exerted by the steam upon the exposed surface of the disc will remain constant, to what- ever amount the outer diameter is relieved of the pressure to its seat, that at and near the centre, forcing it to its seat, will be augmented, until at last the excessive pressure will cause it to cut or abrade, which action will continue until the cutting at and about the centre will allow the larger diameter to bed with more force to its seat, by diminishing the amount of its spring, and hence its resistance to the steam-pressure immediately behind it, whereupon its exces- sive wear would recommence. If, however, the thickness of the disc were made such as to enable it to resist the steam -pressure without springing, the larger diameter would wear sufficiently away to cause the valve to leak ; whereas, if the disc were made suffi- ciently thin to enable it to spring easily, the outer diametei would wear to almost a feather-edge, while the metal about the centre would nearly maintain its original thickness. It is this inequality of wear in revolving, or side, or disc surfaces that is Irn stumbling-block to the success of rotary engines, nor has there as yet been suggested any method of overcoming or compensating for it. It is difficult, indeed, 20 234 COMPLETE PRACTICAL MACHINIST. to perceive in what direction such a remedy can lay, unless it be in making the disc of hardened steel and tempering it, so that being at the outer diameter as hard as fire and water will make it, it is so tempered that it shall be gradu- ally softer as the diameter decreases, until at the centre it is quite soft. Thus the degree of hardness of the metal will be as far as possible in proportion to its liability to wear. In an experiment made by me, I revolved two cast-iron disc-surfaces, of three inches diameter, under a pressure of steam of 20, 35, and 70 Ibs. alternately, per square inch, the surface being pressed together under a pressure of about 7 Ibs. per square inch, and the discs making three thousand revolutions per minute. I found that, in conse- quence of the light pressure, forcing the faces together, a cast-iron surface showed but very little signs of wear not sufficient, indeed, after running ten hours a day for ten days, to efface the scraper-marks from the surfaces, which had become polished and glazed, as it were. Several small holes were then drilled in the contacting surfaces, and plugs of Babbitt metal, brass, wrought-iron, and steel, were inserted, the fr.ces being rescraped all over, and the discs then run as before, the result being that, after two days of running, the cast-iron appeared smooth and bright as before, while the brass, wrought-iron, steel, and Babbitt metal were found to be worn positively below the surface of the cast- iron, several repetitions of the last experiment giving, in each case, a like result. The reason that the liability to cut is found in practice to be much greater in revolving than in reciprocating surfaces is that, when a revolving surface commences to cut, the particles of metal being cut are forced into and add them- selves, in a great measure, to the particles performing the cutting, increasing its size and the strain of contact of the surfaces, causing them to cut deeper and deeper until at least an entire revolution has been made, when the severed DEVOLVING SURFACES. 235 particles of metal release themselves, ami are for the most part forced iiito the grooves made by the cutting. In reciprocating surfaces, when any part commences to cut, the edge of the protruding cutting part is abraded by the return stroke, which fact is clearly demonstrated in either fitting or grinding in the plugs of cocks, in which operation it is found absolutely necessary to revolve the plugs back and forth, to prevent the cutting which inevita- bly and invariably takes place if the plug is revolved in a continuous direction. Furthermore, when a surface revolves in a continuous direction, any grit that may lodge in a speck, hollow spot, or soft place in the metal, will cut a groove and not easily work its way out, as is demonstrated in polishing work in a lathe ; for be the polishing material as fine as it may, it will not polish so smoothly unless kept in rapid motion back and forth. Grain emery used upon a side-face, such as tho outer face of a cylinder-cover, will lodge in any small, hollow spots in the metal and cut grooves, unless the polishing stick be moved rapidly back and forth between the centre and the outer diameter. If a revolving surface abrades so much as to seize and come to a standstill, it will be found very difficult to force it for- ward, while it will be comparatively easy to move it back- ward, which will not only release the particles of metal already severed from the main body, and permit them te lodge in the grooves due to the cutting, but will also dislodge the projecting particles which are performing the cutting, so that a few reciprocating movements and ample lubrica- tion will, in most cases, stop the cutting and wash out the particles already cut from the surfaces of the metal. It is held by many that fast-running bearings filled with Babbitt metal will wear better than brass bearings. Such, however, is not the case, if the bearings are properly fitted ; the only advantage possessed by Babbitt metal bearings is that they are more easily fitted ; because the Babbitt will run so as to make an even and equal bearing upon the ways, the bolt holes (if there are any), the holes for the set screws, the oil holes, etc., so as to have the drilling com- pleted before the straps or rod ends are filed up, because drills leave a burr where they come through the metal, and because the clamps, w r hich hold the work while it is being drilled, are apt to leave marks upon it. The holes should then be tapped, when the rod will be ready for the file. The faces of the rod whereon the straps fit should then be sur- faced with a surface plate, and made quite square with the broad faces of the rod, parallel crosswise with each other, and a little taper with each other in the length. The strap should be made narrower between its jaws than the width of the rod end, so as to require to spring open when placed upon the rod end if the brasses are not in their places. The inside faces of the jaws of the strap must be made quite square with the side faces, so that, when the strap is placed upon the rod end, the latter faces of the strap will not spring out true with the broad faces of the rod end. The rod end must have a light coating of marking rubbed over it, and the strap moved back and forth on it, so that the rod end serves as a gauge and surfacing-block to the strap. If, when the strap is on its place, its side faces are uneven with the side faces of the rod end, as shown in Fig. 255 (which is a sectional view of a strap and rod end, a being the rod end, and B B the jaws of the strap), either one or 314 FITTING CONNECTING RODS. 315 both of the inside side faces of the strap require filing in the direction denoted by the dotted lines, because it is only in consequence of the inside faces not being square with the outside faces that this twist occurs. The key ways in the strap and rod end should be filed out together, that is, while the strap is on its place and secured by being clamped or bolted. If the strap is one held to the rod by a gib and key, the width, from the end of the rod to the crown of the strap when it is placed in position to cut or file out the keyway, should be that of the extreme width of the brasses when the joint of the brasses is close, less the amount of taper there is on the key. The strap, after being fitted to the rod, should be clamped to the rod end, the keyway in the strap and in the rod being placed fair with each other, before the clamp is tightened, for moving the strap after it is clamped will spring it out of true, so that, when the clamp is taken off, the keyways will not be true with each other though they were filed true. In driving in the keys and gibs to fit them, be careful to put a light coat of marking on them, not only to show where they bind but to prevent them from seizing in the keyway. The key and gib placed edgewise together should be parallel on the outside edges, and the keyway should b3 parallel both edgewise and across its width. A thin sheet-iron gauge is better to measure the thickness of the keyway than inside calipers are, and the same gauge will do to plane the key and gib, leaving them a little full in the thickness. The keyways should be surfaced with a surface plate, its breadth being equal to that of the gib and key together when the head of the key is even with the head of the gib ; then when the keyway is finished, and the strap is placed in its intended position on the end of the rod, the strap will have moved back from off the rod end for a distance equal to the amount of the taper on the key, 316 COMPLETE PRACTICAL MACHINIST. so that there will be the requisite amount of draw on the key way of the strap on the one side and on the keyway of the rod on the other side, while the key will at the same time come through the strap to its required distance. The faces of the rod end, whereon the jaws of the strap fit, having been made (as directed) a little taper, and the strap allowed (as described) a little spring, the rod end will enter the strap somewhat easily, and tighten as it passes up the strap, so that, when quite up, the strap will fit a little tighter than it is intended, when finished, to do. When the strap is fitted and keyed to the rod, a light cut should be taken off the faces of the rod and strap while they are together, the bolts of a bolt rod being sufficient to hold the strap for that purpose ; but in the case of a gib and key, a piece of wood should be placed between the rod end and the crown of the strap, that is, in the space intended to be filled by the brasses, .and the wood keyed up so as to lock the strap on . the rod while the faces of the rod and strap are planed. This being complete, the strap is rcaay to receive the brasses. The bottom or back brass must be made to a tight fit, so as to spring the strap open sufficiently to make it fit the rod end as easily as required ; thus both the brass and the strap will be closely fitted. The top brass must be fitted to the strap while the bottom brass is in its place in the strap, and must be made to fit the strap without being so tight as to spring it open. The corners of both brasses where they fit the corners of the strap should be eased away with the edge of a half-round file, so that they will not de- stroy the corners of the strap (when the brasses are being driven in and out to fit), which would make the strap appear to be a bad fit on the rod. While fitting the top brass, it is necessary to try the strap on the rod end (the brasses being in their places) at inter- vals, so as not to take any more off the top brass than is necessary to let the strap fit the rod end. As a guide, when fitting the brasses to the strap, the calipers may be set ti FITTING CONNECTING RODS. 317 the width of the rod end where the strap fits, aiid applied to the strap when the brasses are driven in to fit. The gib and key must, when placed together edgeways, be quite parallel in their total breadth, so that they will fit properly against each other and against the keyway in the rod end and the strap. When setting the gauge for the size to which the brasses are to be planed, place the strap on the rod end to get the correct size, for the strap is narrower (between its jaws) when it is off than when it is on the rod, because of the spring. In bedding the back brass to the strap, let Fig. 256. Fig. 257. it bear the hardest, if anything, upon the crown, for if the bevels of the brass should keep the crown from bedding, the strap would spring away from the rod end, in spite of the gib (or the bolts, if there are any), when the key is driven home, as illustrated in Fig. 256. If the back brass does not bed down upon the crown a of the strap, the latter will spring away from the block end of the rod and from the brasses on the sides, and will assume the shape denoted by the dotted lines. Should the top brass 27 : " 318 COMPLETE PRACTICAL MACHINIST. not bed properly against the rod end, the strap will spring as described in Fig. 257. The dotted line a is the back of the brass, supposed to bed improperly against the rod end, as shown ; the -p. ~ro dotted lines B B denote the manner in which the strap would, in consequence, spring away from the rod end when the key was driven home. If the brasses fail to fit properly against the rod end or strap, in the direction of the breadth of the strap, it will spring out of line, as described in Fig. 258. which is a sectional view of a connecting rod end. C is the strap, D is the rod end, and B B are the brasses, the top one of which, if it did not fit square against the rod end (but on one side only), as represented by the line a, would spring the strap out of true with the rod end, in the direction of the dotted lines. The strap is, by reason of its shape, very susceptible to spring ; and unless the brasses, or even the gib and key, are quite square and fit well, it is certain to spring out of true. The brasses should be a fit on the journal when they are " brass and brass," that is, the joint of the two brasses close together, so as to take the pressure of the key, which thus locks the strap and brasses to the rod end, and prevents them from moving, or working, as it is called, when the rod is in action ; especially is this necessary in straps having a gib and key to hold them to their places, because, if the joint of the brasses is not close, the key cannot be driven home tightly, and hence there is nothing to lock the strap firmly to its place. If, however, the strap is held to its place by bolts, it is not so imperative to keep the joint of the brasses close together, although it is far preferable to do so, especially in the case of fast-running engines, not only on account of the assistance lent by the key to hold the strap firmly, but also because it holds the brasses firmly, and the key cannot bind the brasses too tightly to the journal, even though the key be driven tightly FITTING CONNECTING RODS. 319 home, so as to assist the set screw in preventing it from slacking back. The brasses should be left a little too tight in the strap before boring, because they invariably shrink or go in a little sideways from being bored, as do all brasses, large or small, even if bored before any other work has been done on them. For driving the brasses in and out of the strap to fit them, use a piece of hard wood to strike on so as not to stretch the skin of the brass and alter its form, as already explained in the remarks on pen ing. The brasses should be of equal thickness from the face forming the joint to the back of the brass, so that the joint will be in the centre of the bore of the brasses. The respective faces forming the joint should be quite square with both the faces and sides of the brass, so that they will not spring the strap when they are keyed up, and so that, when the brasses are let together in consequence of the bore having worn, the faces may be kept square, and thus be known to fit properly together without having to put them together in the rod and on the journal to try them, which would entail a good deal of unnecessary labor. To get the length of a connecting rod, place the piston in the centre of its stroke, and the distance from the centre of the crosshead pin to the centre of the crank shaft is the length of the rod from centre to centre of the brasses. Another method is to place the piston at one end of its stroke and the crank on its dead centre corresponding ta the same end of the stroke, and the distance from the cen- tre of the crosshead pin to the centre of the crank pin is the length of the rod. To ascertain when the crank of a horizontal engine is upon its exact dead centre, strike upon the end face of the crank axle or engine shaft a circle true with the shaft, and of the same diameter as the crank- pin : then place a spirit level so that one end rests on the crank pin and the other 320 COMPLETE PRACTICAL MACHINIST. end is even with the outline of the circle ; and when the spirit level stands true, the crank will be upon its dead centre. The length of a connecting rod cannot be taken if the crank is placed in the position known as full power, because the position in which the piston would then be cannot practically be definitely ascertained ; for the angle at which the connecting rod stands causes the piston to have moved more or less than half the length of the stroke when the crank has moved from a dead centre to full power, according to which end of the cylinder the piston moved from. If it was the end nearest to the crank, the piston moved less, if the other end, it moved more, than half of its stroke ; so that in either case the piston stands nearer the crank than is the centre of the length of the cylinder when the crank is in the position referred to. This variation of piston movement to crank movement is greater in the case of short connecting rods than with long ones. To fit a connecting rod to an engine, first rub some marking on the crank pin, and put the crank pin end of the rod on its place, with the brasses in and keyed prop- erly up. The other end of the rod, being free, can be placed so as to touch against the crosshead pin, when the eye will detect if it will go into its place without any spring sideways ; if it will do so, the rod may be taken off the crank pin, and the brasses, if necessary, fitted to the pin sufficiently to allow each to bear on the crown. But if the rod end will not fall into the crosshead journal without being sprung sideways, then move it clear of the cross- head, placing a side pressure on it in the direction in which it wants to go to come fair with the crosshead journal, and move it back and forth under such side pressure, which process will cause the crank pin to mark where the con- necting rod brasses want filing and scraping to bring the rod true. The rod must then be taken off, and the brasses FITTING CONNECTING RODS. 321 eased where the marking and the knowledge of which way the rod ought to go determine, the rod being placed on the crank pin as before, and the whole operation repeated until the rod "leads" true with the crosshead journal. The crosshead end of the rod must be fitted in like manner to the crosshead journal until the crank piii end of the rod leads true to the crank pin journal. The rod must then be put on its place, with both journals keyed up, and, if it can easily be accomplished, the engine moved backwards and forwards, the brasses being then taken out and bedded, when the rod will be fitted complete. A connecting rod which has both straps held by gibs and keys gets shorter from centre to centre of the bore of the brasses as it wears, and that to half of the amount of the wear. This is, how- ever, generally rectified by lining up the brasses that is, placing pieces of metal behind them (they may be fastened to the brasses if it is desirable) which pieces are made of the required thickness to replace the amount of the wear of the brasses. A connecting rod whose crosshead end has a strap with a gib and key, or, what is better, two gibs and a key, to hold it, the crank pin end having its strap held by bolts, and the key between the bolts and the brass, would maintain its original length, providing the wear on the crosshead brasses was as great as is the wear on the crank pin brasses ; but since that on the latter is the greatest, the rod wears longer to half the amount of the difference of the wear between the crosshead and crank pin journals. If both the straps of a rod are held by bolts, the key of one end being between the brasses and the main body of the rod, and the key of the other end between the brasses and the crown of the strap, it would maintain its original length if the wear on both ends was equal ; but this not being so, it wears longer, as above stated. When mark- ing the length of the rod (that is, the circle on the brasses to set them by for boring), or when trammeling a j>.d *o try 322 COMPLETE PRACTICAL MACHINIST. its length, stand it on its edge ; because if it rests on its broad i'ace the rod will deflect, and appear to be shorter than it is ; this is especially liable to occur in coupling or side rods, which are generally longer and slighter in body than connecting rods. The oil hole of a strap for either a connecting or side rod should be in the exact centre of the space intended to be filled by the brasses. It will thus be central with the joint of the brasses, and from centre to centre of the oil holes, and will, therefore, represent the proper length of Fig. 259. the rod. If the oil hole of the strap has been drilled to give the rod length as already explained, and new brasses have been fitted in, the bore may be marked out as in Fig. 259, there being a piece of wood or metal driven in the bore, and the line E being carried down by a try- square, and marked at D ; lines A and B are obtained from the inside faces of the strap jaws, and from these the center is obtained, wherefrom to mark a circle to set the brasses by when chucking them to be bored . In some cases, however, the brasses do not abut one FITTING CONNECTING RODS. 323 against the other, but are left open as in Fig. 260, and in this event the piece of wood must be placed across the bore as denoted by D in Fig. 260, the line B representing the center of the oil hole or the length of the rod. The brasses should be so filed that lines as A in the Fig. 260. figure marked level with each face will be equidistant from B, and to accomplish this result, each brass must be laid upon a surface plate and tested with inside calipers, as in Fig. 261. In letting brasses together to take up the wear, we must Fig. 261. in brasses that abut against each other, or cone brass and brass, as it is termed, try them with calipers, applying the square both ways on the joint faces, for if the joint faces are at an angle instead of being square across, then driv- ing up the key will spring the brass faces out of level one with another. Or if the faces are out of square instead 324 COMPLETE PRACTICAL MACHINIST. of being square across, then driving home the key will spring the strap jaws open sideways. In lining up brasses to set the key up in such a rod end Fig. 262. as is shown in Fig. 262, the liner L will be the one that determines the rod length, that at E simply serving to regulate the key height and not affecting the rod length. Fig. 263. P But when the strap is bolted to the rod end, as in Fig. 263, the back liner at L determines the rod length, and that at E is the one that raises the key. VISE- WORK DRIFTS. 325 DRIFTS. Of drifts there are two kinds, one being a smooth round conical pin, employed by boiler makers to make the punched holes in boiler plates come fair, so that the rivets may enter, which may be aptly termed a stretching drift, and the other the toothed or" cutting drift. Of the first it is to be observed that in some modern practice the holes in boiler plates are drilled, and are therefore more accurately spaced than it is practicable to punch them, thus greatly reducing the necessity to drift them; fur- thermore in the best practice the drilling is done after the plates have been bent into shape, thus dispensing altogether with the use of the drift-pin, which in the case of the badly matched holes found in punched plates greatly impairs the strength of the rivetted joint. The punching of a plate considerably weakens its strength at the narrow- est section of metal, namely, between the hole and the edge of the plate, where the latter, being the weakest, gives way to the pressure of the punch. If one closely observes the surface of a piece of iron which is being punched, he will find that the scale on the surface of the iron round the hole, and especially between the hole and the edge of the plate, will be sensibly disturbed, showing a partial disinte- gration of the grain of the metal beneath, even if the punch is very sharp ; but if the punch is dull, or the edge is in the least rounded by wear, the scale will fly off the surface of the metal in small particles, evidencing a considerable disturbance of the metal beneath and an equivalent weak- ening of the substance between the edge of the hole and the edge of the plate. If, then, after punching, the holes do not come fair, and the plain drift is employed to still further stretch the metal, not only is the weakening pro- cess greatly augmented, but the holes are stretched oval, so that the rivets do not completely fill them, however well the riveting may be performed. The use of the plain drift is therefore totally incompatible with first-class work- 28 326 COMPLETE PRACTICAL MACHINIST. manship ; hence a description of this tool will be altogether omitted. Of cutting drift?, there are two kinds, the first being that shown in Fig. 264. A is the cutting edge, the width and thickness at C and B being reduced so that the sides of the drift may clear the sides of the hole. The drift is filed at A A, to suit the required hole, and tempered to a brown bordering upon a purple. The hole or key way is then cut Fig. 264. Fig. 265. out roughly, to nearly the required size, and the drift is then driven through with a hand hammer, cutting a clean and true hole. Care must, however, be taken to have the work rest evenly upon a solid block of iron or (for delicate work) lead, and to strike the punch fair and evenly, other* wise a foul blow may break the drift across the section at C. This class of drift is adapted to small and short holes VISE- WORK DRIFTS. 327 only, such as cotter ways in the ends of keys or oolts, for which purposes it is a very serviceable and strong tool. It must be freely supplied with oil when used upon wrought- iron or steel. For deeper holes, or those requiring to be very straight, true, and smooth, the drift represented by Fig. 265 is used. The breadth and thickness of the section at A is made to suit the shape of the keyvvay or slot required. The whole body of the drift is first filed up parallel and smooth, to the required size and shape; the serrations forming the teeth are then filed in on all lour sides, the object of cutting them diagonally being to preserve the strength of the cross section at A A. The teeth may be made finer, that is, closer together, for very fine work, their depth, however, being preserved so as to give room to the cuttings. To attain this object in dr if to of large size, the teeth should be made as shown in Fig. 265, which will give room for the cuttings, and still leave the teeth sufficiently strong that they do not break. The head B of the drift is tapered off, so that, when it swells from being struck by the ham- mer, it will still pass through the hole, since this drift is intended to pass clear through the work. The method of using this tool is as follows : The holo should be roughed out to very nearly the required size, leaving but a very little to be taken out by the drift, whose duty is, not to remove a mass of metal, but to cut a true and straight hole. To assist in roughing out the hole true, the drift may be driven lightly in once or twice, and then withdrawn, which will serve to mark where metal re- quires to be removed. When the hole is sufficiently near the size to admit of being drifted, the work should be bedded evenly upon a block of iron or lead, and oil sup- plied to both the hole and the drift ; the latter is then driven in, care being exercised that the drift is kept up- right in the hole. If, however, the hole is a long one, and the cuttings clog in the teeth, or the cut becomes too great, 328 COMPLETE PRACTICAL MACHINIST. which may be detected by the drift making but little progress, or by the blow on the drift sounding solid, the drift may be driven out again, the cuttings removed, the surplus metal (if any there be in the hole) cut away, the hole and drift again freely oiled, and the drift inserted and driven in as before, the operation being continued until the drift passes entirely through the hole; for the drift- will be sure to break if too much duty is placed upon it, After the drift has passed once through the hole, it should be turned a quarter revolution, and again driven through, and then twice more, so that each side of the drift will have contacted with each side of the hole (supposing it to be a square one), which is done to correct any variation in the size of the drift, and thus to cut the hole true. The great desideratum in using these drifts is to drive them true, and to strike fair blows, otherwise they will break. While the drift is first used, it should be examined for straightness at almost every blow; and if it requires drawing to one side, it should be done by altering the direc- tion in which the hammer travels, and not by tilting the hammer face (see Fig. 266). Suppose A to be a piece of work and B and C to be drifts which have entered the keyways out of plumb, as shown by the dotted lines D and E. If, to right the drift C, it was struck by the hammer F, in the position shown and travelling in the direction denoted by G, the drift C would be almost sure to break ; but if the drift B was struck by the hammer H, as shown, and travelling in the direction denoted by I, it would draw the drift B up- right without breaking it; or in other words, the hammer face should always strike the head of the drift level and true with it, the drawing of the drift, if any is required, being done by the direction in which the hammer travels. When it is desired to cut a very smooth hole, two or more drifts should be used, each successive one being a trifle larger in diameter than its predecessor. Drifts slight in REVERSE KEYS. 329 cross section, or slight in proportion to their lengths, should be tempered evenly all over to a purple blue, those of stout proportions being made of a deep brown bordering upon a bright purple. For cutting out long narrow holes, the drift has no equal, and for very true holes no substitute. /; It must, however, be very carefully used, in consequence of its liability to break from a jarring blow. REVERSE KEYS. Crossheads, pistons, and other pieces of work which are keyed to their places upon taper rod ends, and are therefore 28 330 COMPLETE PRACTICAL MACHINIST. apt to become locked very fast, are easily removed by nieaDS of reverse keys, which should always be employed for that purpose, because striking such work with a ham- mer, even supposing the work to be well supported under- neath and copper interposed between the hammer and the work, is liable to bend and otherwise damage it with every heavy blow. Reverse keys are simple pieces of steel, so shaped as to reverse the draft of a key way, and are made male and female, as shown in Fig. 267, A representing the male, and B the female. The manner of using them is to insert them into the keyway, as shown m Fig. 268, in which A Fig. 267. Fig. 268. B T A I represents a taper rod end, B the socket into which A is fitted or keyed, C the male and D the female reverse key, and E an ordinary key. It will be found, on examination, that the insertion of C and D have exactly reversed the position of the draft of the keyway, so that the pressure due to driving in the key will be brought to bear upon the rod on the side on which the pressure was previously on the socket, and on the socket on the side on which the pressure was on the rod ; so that driving in the key will key the socket out of instead of into its place. The keyway in Fig. 268 is shown to have draft ; that is, the proper key, when driven in, will bear one edge upon SETTING LINE-SHAFTING IN LINE. 331 the edge of the keyway in the rod only, and not on the edge of the keyway in the socket at the small end of the cone ; while at the large end, the natural key would bear against the edge of the keyway in the socket only. If however, this condition does not exist, and the edges of the key bear equally upon the cone and the socket (on both edges and all the way through), the keyway being a solid one, that is to say, having no draft, the reverse keys may be employed, providing that C is placed so as to bear upon the edge of the keyway on the large end of the cone only, and that D is placed to bear on the edge of the keyway at the small end of the cone on the socket only, thus pro- ducing a back draft, or clearance, as it may better be termed. The key E should be made long, and both it and the reverse keys should be made of steel and left soft. SETTING LINE-SHAFTING IN LINE. To set a length or line of shafting in line, first prepare a number of wooden frames or targets, such as in Fig. 1 <. ^ 7 r. 269. I 1 .! 1 Hfi 5 A 1 1 } '\ 'l / *'/ r^^^^i^^ 9 / ' ; ~^~'^^t== 269, the outer edge A being planed straight, and there being marked a line B parallel to A. Upon this frame hangs the plumb-bob, shown at B, so that when the plumb line is fair with the marked line the edge A will stand vertical. Having erected these targets at each end 332 COMPLETE PRACTICAL MACHINIST. of each length of shafting, we stretch a fine string or silk line beside the line of shafting, as in Fig. 270, fig. 270. placing it about 6 inches below and on one side of the shafting, and adjusting it at first as nearly parallel to the Fig. 271. shaft as can be judged by the eye. If the line of shafting is of equal diameter at each end, we may set the stretched SETTING LINE-SHAFTING IN LINE. 333 liiie equidistant from it at each end ; while if one end is of larger diameter than the other, we set the line parallel to the shafting axis, and horizontally true as near as it can be set by a spirit level. The targets must now be ad- justed as follows: the planed edge is brought up so as to just touch the stretched line, while its edge A is vertical, which will be known from the plumb line covering the line marked beneath it and parallel to edge A. Each target is set in this way and nailed fast or secured in any con- Fig. 272. veuient manner, as in Fig. 271. We have now in the planed edges A of the target a substitute for the stretched line, and forming a guide for the horizontal adjustment of the line of shafting. For the vertical adjustment we take a wooden straight-edge long enough to reach from one 'target to the next one, and beginning at one end of the shafting we place the flat side of the straight-edge against the planed edges of two of the targets at a distance of say 15 inches below the top of the shafting, and after levelling S34 COMPLETE PRACTICAL MACHINIST. i. the straight-edge with a spirit level, we mark even with the edge of the straight-edge a line on the planed edge A of both of the targets. We then move the straight-edge so as to embrace the next target, set one end even with the line already marked on the second target, and set it Fig, 273. true by a spirit level and mark a line on the edge of the third target, the straight-edge being shown in Fig. 272, in position to mark the line on the third target. By continuing this process we shall have marked a line across the edges of all the targets, and from this line the shafting may be set as follows : A square having its edges, A and B, at a right angle to one another has a line C marked upon it at a distance below the edge A of 15 inches (this being the distance we set the stretched line below the shafting axis), from line C on the square as a centre we mark below it a line F, in Fig. 273, distant from C to an amount equal to half the diameter of the line shaft, and if the shafting is parallel in diameter we may rub out line C and leave line F only on the square. All that remains to do is to apply the square to the edge of each target, and to the shaft, and when the line on the square coincides with the line on the target, the shafting is set true and level. For the horizontal adjustment all we have to do is to place a straight-edge on the edge of the target, as in Fig. 274, and adjust the shaft by a distance-piece D. There are several points, however, during the latter part of the process at which consideration is required. Thus, after the horizontal line, marked on the targets by the straight-edge and used for the vertical adjustment, has been struck on all the targets, the distance from the Fig. 274. SETTING LINESHAFT1NG IN LIKE. 335 centre of the shafting to that line should be measured at each end of the shafting, and if it is found to be equal, we, may proceed with the adjustment. But if, on the other hand, it is not found to be equal we must determine whether it will be well to lift one end of the shaft and lower the other, or make the whole ad- justment at one end by lifting or lowering it as the case may be. In coming to this determination we must bear in mind what effect it will have on the various belts, in making them too long or too short, and when a decision is reached, we must mark the line C, in Fig. 273, on the gauge, accord- ingly, and not at the distance represented in our example by the 15 inches. The method of adjustment thus pursued possesses the advantage that it shows how much the whole line of shafting is out of true before any adjustment is made, and that without entailing any great trouble in ascertaining it; so that in making the adjustment the operator acts intelligently and does not commence at 6"ne end utterly ignorant of where the adjustment is going to lead him to when he arrives at the other. Then, again, it is a very correct method, nor does it make any difference if the shafting has sections of differ- ent diameters or not, for in that case we have but to measure the diameter of the shafting, and mark the adjusting line, represented in our example by C, in Fig. 273, accordingly, and when the adjustment is completed, the centre line of the whole length of the line of shafting will be true and level. This is not necessarily the case if the diameter of the shafting varies and a spirit level is used directly upon the shafting itself. In further explanation, however, it may be well to illustrate the method of applying the gauge shown in Fig. 273, and the straight-edge C and gauge D, shown in Fig. 274, in cases where there are in 336 COMPLETE PRACTICAL MACHINIST. the same line sections of shafting of different diame- ters. Suppose then that the line of shafting in our exam- ple has a mid-section of 2-J inches diameter, and is 2 inches at one, and 2 inches in diameter at the other end. All we have to do is to mark on the gauge, shown in Fig. 273, two extra lines denoted in the Fig. by D and F. If the line C was at the proper distance from A for the section of 2| inches in diameter, then the line D will be at the proper distance for the section of 2 inches, and Eat the proper distance for the section of 2^ inches diameter, the distance between C and D, and also between C and E, being \ inch ; in other words, half the amount of. the difference in diameters. In like manner, for the horizontal adjustment, the gauge piece shown at D, in Fig. 274, would require, when measur- ing the 2^ inches section, to be \ inch shorter than for the 2^ inches section, while for the 2 inches section would require to be | inch shorter than that used for the 2 inches section, the difference again being J the amount of the variation in the respective diameters. Thus the whole process is simple, easy of accomplishment, and very accurate. If the line of shafting is suspended from the posts of a ceiling instead of from uprights, the method of procedure is the same, the forms of the targets being varied to suit the conditions. The process only requires that the faced edges of the targets shall all stand plumb and true with the stretched line. It will be noted that the plumb lines (shown on the target in Fig. 269 at B) are provided simply as guides, whereby to set the targets, and are put at about | inch inside of the planed edge so as to be out of the way of the stretched line. It is of no con- sequence how long the stretched line is, since its sag does not in any manner disturb the correct adjustment; but in cases where it is a very long one it may be necessary to SETTING LINESHAFTING IN LINE. 337 place pins that will prevent it from swaying by reason of air currents or from jarring. The same system may be employed for setting the shaft- ing hangers, the bores of the boxes being used instead of the shafting itself. 29 CHAPTER XVI. MILLING-MACHINES AND MILLING-TOOLS. THE position occupied by the milling-machine in modern practical mechanics is almost as important as that occupied by the lathe or planing-machine. In getting out work by the aid of either of the latter, the size and uniformity of the work depend upon the accuracy in measurement, and hence upon the skill of the operating artisan, hence a skilled and expert workman is necessary to the use of each lathe or planer. In the case, however, of a milling- Flg. 275. machine, the skilled mechanic has but to properly set the machine and the chucks necessary to hold the work, and a less skilful operator may be assigned to continue the opera- tion of getting out any number of similar pieces of work, with the assurance that uniformity of size and form and equality of finish may be, with ordinary care, assured. Then, again, intricate forms and shapes of work may be exactly and easily duplicated by the employment of 338 MILLING MACHINES AND TOOLS, 339 milling-tools, which would be impracticable were the same work operated upon by a planing-machine ; especially is this the case in work of complicated form. Suppose, for instance, it were required to cut out a corrugated surface, such as shown in Fig. 275, it would be a difficult matter to produce, with a planing-machine, one such a piece of work 340 COMPLETE PRACTICAL MACHINIST. quite true and with a smooth and polished surface, because the tool would be liable to spring from the broadness of cutting surface, which would, in the case of wrought-iron and steel, cause the tool to spring into the softer and away from the harder parts of the metal ; and in the case of any metal it would be quite difficult to feed the tool so as to insure exactitude and avoid tool-marks at the junction of the cuts taken by the round-nosed and curved tools; whereas, with a milling-tool, properly made (and it is no difficult matter to make such a tool), the operation is so simple that it may be per- formed with comparatively Fig. 278. unskilled labor. One of the main advan- tages of milling-tools is that the work will, in nearly all cases, be true, even, and smooth, even though the tool itself be a little out of true. Suppose, for example, we require to mill the side faces of a rod, and we em- ploy for the purpose the milling-bar and cutters shown in Fig. 277, in which A represents the spindle of a milling-machine, and B B are milling-cutters with the distance washer C interposed between them to regulate their distance apart; D representing a piece of work being fed between the revolving cutters B B. Now, it is evident that even were the cutters out of true, the pieces of work would all be cut to one size, because the projecting teeth of the cutters will come into contact with and operate upon each part of the surface of the work being operated upon, the only difference being that the work will be cut nar- rower with the same thickness or length of washer than it would be were the washers true. MILLING MACHINES AND TOOLS. 341 In Fig. 276, E represents a view of the face of a milling- cutter, and F a sectional view of the same, while G repre- sents a piece of work passing under the cutter and not between the cutters, as shown in the case of the work B. The arrow H denotes the direction in which the cutter E would require to revolve, and the arrow I the direction in which, in that case, the work would require to travel ; from which it will be perceived that the lateral strain placed upon the work by the cut is in a direction to force the work back from the cutter, and this must always, in the use of milling-tools, be the case, and is a very import' ant consideration for the following reasons : From the breadth of cut taken by a milling-tool, and from the acute angle at which the teeth of the cutter strike the cut when the work passes below the circumference of the cutter, the strain due to the cut is immense ; and were this strain in a direction to drag or draw the work below or towards the cutter, the latter would, from the spring of the spindle, rip into the work and tear its own teeth off. Thus, in Fig. 278, suppose A to be a milling-cutter revolv- ing in the direction of the arrow B, and C to be a piece of work travelling in the direction of D, it will be readily perceived that there will be an enormous strain in a direction to force the work from its chuck or clamps and drag it under the cutter. The work being held sufficiently firm, cannot, it is true, move in that direction faster than the rate of feed will permit ; but the teeth grip the work, the cutter springs forward and attempts to ride like a spiked wheel over the work, and the cutter-teeth break from the undue pressure ; and therefore it is that in milling work of every kind whatsoever, the direction in which the work is fed should be such as to tend to force the work away from the cut ; or, in other words, the cutters should cut under the cut, not only because of the above imperative reasons, but for the tbl lowing additional ones : 29 1 - 842 COMPLETE PRACTICAL MACHINIST. The skin of iron or brass castings and of iron or steel forgings is considerably harder than is the interior of the metal, in addition to which there is frequently scale in the one case and sand in the other to contend with, so that if the cutting edge of a tool comes into contact with the outer skin of the work, the keenness, and hence the cutting value of the tool or cutter, becomes rapidly impaired ; and milling-cutters being expensive tools to make, it is desirable that their cutting edges and qualifications be preserved as long as possible. Suppose, therefore, that in Fig. 270, from A to B represents the depth of cut on two Fig. 279. J) pieces of work, one travelling beneath the cutter in the direction of the arrow C, and the other in the direction of the arrow I), and that the upper surfaces B, in each case, have a hard surface-skin upon them : it becomes apparent then that in the case of the piece represented at 1, the cutter- MILLING MACHINES AND TOOLS. 343 teeth will, after the cut has once started, meet the soft metal and cut under the skin till the cut has ended, so that, save at the very commencement of the cut, the cutter- teeth would never meet or come into contact with the hard surface-skin ; while in the case of the piece of work 2 the teeth would in every instance strike the hard skin first. If the piece of work E were held in the position shown, it would strike the scale, whichever way the cutters ran or the work was fed ; and the same remark applies to the piece of work F. There is this difference, however, between the two latter positions : with the cutter revolving in the direction shown, the strain of the cut would be in a direc- lion to lift E from the machine-table, rendering it very liable to spring and difficult to cut ; while the strain on F would tend to force it down upon the table, which would be far preferable. When the side faces of the cutters operate, they must be made right and left that is to say, the teeth of one cutter must slope in the opposite direction to those on the other cutter, so that when the two are placed opposite to one another, as shown in Fig. 277, the teeth of both will stand in a direction to accommodate the direction in which the cutters revolve. To cut side faces of any required width, we have only to vary the width apart of the cutters by the washer C, in Fig. 277; while, to cut curves and shoulders, the periphery only of the cutters can be used. Thus, sup- pose it were required to cut out the form shown in Fig. 280, the outline of the cutter would require to be as shown in Fig. 281, but it would be a tedious and difficult matter to get up a solid cutter of such a fhape on account of the difficulty of cutting the teeth; hence, all such compound forms are produced by making separate cutters, each of its requisite form, size and width, and then placing them together to make up the whole. Thus the figures from 1 to 8 each represent a separate cutter. It is obvious then that there is scarcely a limit to the forms cnpible of being 344 COMPLETE PRACTICAL MACHINIST. .Ffy.281. smoothly cut and uniformly reproduced by such cutters. The Morse Twist Drill Company cut the threads upon their taps, and give the sides of threads a slight amount of clearance back from the cutting edges by the use of mil ling- tools, producing a tap equal in every respect to those producible in the lathe, and being re- p ig 280 . markable for uniform- ity of size and finish. Milling-cutters of small size are made of solid cast-steel ; for larger sizes, the body is made of wrought-iron, while the faces whereon the cutting-teeth are to be formed have steel welded on them. After the cutters are bored and turned to the requisite size and shape, the spaces neces- sary to the formation of the teeth may be cut by a milling-cutter ; and here it may be well to note that it is advisable to keep the teeth sufficiently wide apart to give plenty of room for the cuttings to escape; even in cutters for gear-wheels, coarse teeth that is, those wide apart will cut quicker and smoother than fine ones, and have the advantage that they entail much less labor in both the manufacture when new and resharpening when dull. After the spaces are cut out and MILLING MACHINES AND TOOLS. 345 the teeth formed, the cutter must be carefully hardened and tempered to a straw color. Very long toothed cutters, such as reamers, are apt to warp in the hardening, getting out of round as well as out of straight. They may of course be made true again, by the ordinary grinding process, or the following plan may be adopted to straighten them previous to sharpening them in the usual manner: The reamer, after being hardened, should be revolved rapidly in the lathe in one direction, while an emery- wheel revolves at a high speed in the opposite direction, as shown in Fig. 282, A representing the reamer and B the emery-wheel ; the emery- Fi(j. 282. wheel should be fed to the reamer just sufficient to true the cutting edges. For ordinary cutters clearance and sharpening may be given to the teeth as follows : Beneath a re- volving emery-wheel, and quite parallel and true with the spindle on which the emery-wheel revolves, there is provided a stationary adjustable mandril of such a size as to neatly fit the centre hole in the cutter to be operated upon ; which mandril is of a sufficient length to permit the cutter to slide along it and stand wholly on either side of the emery-wheel. The height of the mandril is adjusted so that the emery-wheel will, when brought into contact with the cutter Awhile the latter is upon the mandril), take off just sufficient to sharpen and give clearance to the teeth. Some guide is necessary to insure that the teeth of the cutter shall pass under the emery-wheel in an exactly uniform position, which is accomplished by providing an adjustable stationary guide or gauge, against which the radial or front face of the tooth is held while it is being 346 COMPLETE PRACTICAL MACHINIST. ground. The operation is thus to place the cutter on the mandril and adjust the latter to the requisite height, tc then adjust the guide so that when the cutter is moved forward it will first come into contact with the guide, against which the cutter is held by the hand, while it is at the same time passed under the emery-wheel. It is obvi- ous that by this means either circumferential or side face teeth may be sharpened and maintained true if the bear- ing of the cutter upon the mandril is sufficiently long and of sufficiently accurate fit to keep the cutter steady. There are other devices for taper cutters in which the latter are stationary and the emery-wheel traverses along the teeth, which plan is for taper cutters preferable to that first described ; the principles involved are, however, the same in both cases. It must be remembered that, in using the emery-wheel for this purpose, it must run under its cut for the reasons already explained by Fig. 278 and its accompanying ex- planation. It is obvious that in the case of long cutters having cir- cumferential teeth, the excessive strain due to each tooth striking the cut will cause the mandril carrying the work to spring away from the cut, the effect being that the fin- ished surface of the work will be slightly waved. To remedy this defect, the teeth of the cutter should be made to run slightly spiralled, and not straight across the length of the cutter, so that the cutting edges will be taking and leaving the work continuously, and hence the spring above referred to will be at all times equal. The same object is obtained in compound cutters, such as shown in Fig. 281, by cutting the key or feather-ways in the cutters, so that their teeth will not stand in a line one with the other. CHAPTER XVII. GRINDSTONE AND TOOL GRINDING. GRINDSTONES are employed for three purposes: to smooth surfaces, to reduce metal to a given thickness, ana to sharpen edge tools. The following are the various kinds of grindstones, and the uses for which they are best suited : Ohio, Nova Scotia and English stones are,those princi- pally n?ed, and each of these are cut to various sizes, and have different degrees of coarseness and fineness of grit. New Casile stones have a yellow color and sharp grit, the fine sofc ones for grinding saws to gauge thickness, and the coarser for rougher work, as grinding sad-irons and springs, for face stones in nail works, and for castings (dry grinding). Wickersly, grayish-yellow color, for saws and cullers' work generally, having a very soft grit and hence not liable to heat the work and draw its temper. Liverpool (or Melling"), of a red color and very sharp grit, for edge tools generally. Nova Scotia, blue or yellowish gray color, being of all grits from the finest and hardest to the coarsest and softest, used for general grinding as well as for machinist tool grinding. Bay Chaleur (N. B.), of a uniform blue color and soft sharp grit, for cutler)' and for fine edge tools. Independence, grayish white color, soft loose grit, for edge tools requiring a fine edge, and for the dry grinding of castings. Huron (Michigan), of a uniform blue color and fine sharp grit, best suited for tools requir- ing a fine sharp edge as carpenters' tools. It is desirable that the fineness or coarseness of the grit be uniform 347 348 COMPLETE PRACTICAL MACHINIST. throughout the stone, because a hard spot will wear the least and become a projection, while a soft one will wear the quickest and become a depression, either of which is a defect preventing the production of true and smooth grinding. A stone having a coarse open grit will ctit the most freely and remain the most true, but will not last so long. Stones having a close though coarse and hard grit are apt to become coated with particles of the metal cut from the work, which is remedied by grinding a round iron bar of small diameter, the small area of contact acting to dislodge the particles and clean the stone. Grindstones that are used wet (as is generally the case) should be kept supplied with water when in use, but not allowed to stand. in water when at rest, because the part immersed will absorb water and become the hardest, which will cause it to wear the least, thus throwing the stone out of true. Furthermore, if the stone be overrun at a quick speed the side that is water-soaked becomes the heaviest, and this may throw the stone sufficiently out of balance to cause the unequal centrifugal force generated at a high velocity to burst the stone. The surfaces of stones used for sharpening machinists' tools should be kept as smooth as possible, while those used for removing metal or taking the skin from metal or similar work, where the object is to remove the metal as quickly as possible, are what is termed hacked; that is, they have indentations cut in them with a tool similar to a car- penter's adze. This hacking is usually performed most on the high parts of the stone, so as to cause them to wear the most and by this means keep the stone true. This class of stone is usually of the harder and coarser kinds of grit, the diameter of the stone ranging from 5 to 6 feet, and the face from 7 to 12 inches wide, and are rim at speeds someti tries as great as 2000 feet per minute. GEINDSTONE AND TOOL GRINDING. 349 A grindstone should run as true as it is practicable to \iave it. This is attained by either fitting to the stone truing devices, or truing the stone (at intervals) by hand. Sometimes two stones are so set as to enable their perime- ter to touch, the speeds of rotation varying (or the direc- tion of rotation may vary) ; hence one stone keeps the other true. In this case the best results are obtained when one stone only is used, the other (which may be a small one) being a truing stone, which is preferably caused to traverse laterally back and forth across the other stone so as to keep the face of both stones at a right angle to their planes of' rotation. In some cases grindstones are fitted with traversing rests which hold the work and traverse it back and forth between two grindstones. One of the two stones is speeded up to about 2000 feet per minute to perform the grinding, and the other (usually of smaller diameter) is driven by a gear wheel so as to hold the work from rotating or cause it to rotate at a slow speed, as about 80 feet per minute. The smaller stone is so carried that it may be traversed to or from the larger one, to suit different thick- nesses of work and to put on the cut. For very accurate grinding, as for grinding the surfaces of engravers' plates, the grindstone is, in the best practice, mounted upon a machine somewhat similar to a planer the rotating stone occupying the position of the planer tool. The work, however, simply lies upon the table and is traversed back and forth beneath the stone by hand, which obviates the spring that would ensue from the pressure of work-holding devices. A grindstone, for tool grinding, having no truing device, may be turned up with a piece of hardened steel or a piece of gas or other iron pipe about f inch in diameter. A piece of iron is laid across the grindstone trough to form a rest, and the tool or pipe is held at a considerable f\ngle to the stone, the cutting end being well below the 30 350 COMPLETE PRACTICAL MACHINIST. surface of the trough. By this means the pipe is not liable to take too deep a cut or to be wrenched from the hand?, as it will give way somewhat to the projections on the stone. The tool should be about 4 to 5 feet long, and should be fed to its cut by being slowly revolved, which will not only feed it but also keep the end of the tool square as is necessary. It should be pressed firmly down to the fulcrum bar or rest to prevent it from slipping. After the stone is turned true and to shape it should be smoothed by the edge of a straight thin piece of sheet- Fig. 283. iron, which .should be moved laterally, to prevent the edge from grinding, to fit the projecting rings on the stone. During this turning operation the stone should be quite dry and should revolve at a slow speed, and, to prevent the pipe from becoming red hot, it should be occasionally dipped in water. The intermittent truing of a stone is, however, objec- tionable, because for the proper sharpening of tools the stone should be kept continuously true, and for this pur- pose we have the device shown in Fig. 283. It consists of a frame carrying a threaded hardened steel roll bolted to the trough, as in Fig. 284. GRINDSTONE AND TOOL GRINDING. 351 The piece carrying the roll is pivoted below the roll, hence -by turning the screw (by means of the hand wheel shown) the roll is brought into contact with the stone surface, the thread crushing the projections on the stone and thus keeping it true. The friction between the sur- faces causes the threaded roll to revolve and prevents its rapid wear. The advantage of this device is that the stone may be kept true while in constant use, and, as the device works with water, the dust and dirt due to turning Fig. 284. with a tool is avoided ; furthermore, the stone is maintained irue across its width, which is highly advantageous in grinding machinists' tools, especially those for coarse feeds where it is difficult to grind the nose of the tool flat and straight. Since the device can be applied to or disengaged from the grindstone surface at pleasure it does not unduly wear it away, and indeed causes, if properly is seel, no more wear than is essential to keep the stone true. The device should be placed upon that side on which the stone leaves the trough when rotating. 5132- COMPLETE PRACTICAL MACHINIST. If a stone does not run true the tool will dip into the depressions and rise over the projections, rendering the operation unsteady ; rounding the tool facet, and destroy- ing the flatness that is necessary to the production of a keen cutting edge. The face of a grindstone for flat surfaces may be flat across, or slightly rounding, as in Fig. 285, but in no case hollow, as in Fig. 286, for reasons which will be explained presently. If in grinding a tool it is held in such a position that the circumference of the stone runs towards the operator, the grinding can be performed quicker and, as a rule, Fig. 285. Fig. 283. better; but it is, in many cases, quite dangerous, because the edge of the tool is liable to catch in any soft places or spots in the stone and to be dragged from the operator's fingers; sometimes it will force them down with violence to the tool-rest, rendering them liable to injury by being caught between the rest and the stone. The rest should l>e bolted firmly to the trough, and should stand on such gide of the stone that the stone runs towards the top of the rest, this top also being above the level of the centre of the stone. In determining upon which side of the stone any given tool should be ground., the workman takes into considera- GRINDSTONE AND TOOL GRINDING. 353 tion the following: the shape of the tool, the amount of metal requiring to be ground off, and the condition of the grindstone. Upon the edge of a tool which last receives the action of the stone, there is always formed what is termed a feather edge, that is to say, the metal at the edge does not separate from the body of the metal, but clings thereto in. the form of a fine ragged web, as shown in Fig. 287, in which A represents a grindstone running in the direction Fig. 287. ^f the arrow, B, and C represents a tool. If now we take a point on the circumference of the stone, as say at F, it should leave contact with the tool at the point denoted by D; instead of doing this, however, the metal at the ex- treme edge of the tool gives way to the pressure and does not grind off, but clings to the tool, leaving a web, as shown from D to E ; whereas, if the same tool were held in the position shown at G, the stone would meet the tool at the edge first, and would cut the metal clear away and not leave a feather edge. 3D Now the amount of the feather 354 COMPLETE PRACTICAL MACHINIST. edge will be greater as the facets forming the edge stand at a more acute angle one to the other, so that, were the facets at a right angle (instead of forming an acute wedge, as shown in Fig. 287) the feather edge would be very short indeed. But in all cases the feather edge is greater upon soft than upon hard metal, and is also greater in propor- tion as the tool is pressed more firmly to the stone; hence the workman conforms the amount of the pressure to suit the requirements by making it the greatest during the early grinding stage when the object is to grind away the surplus metal, and the least during the later part of the process, when finishing the cutting edge, and hence he obtains a sharper tool, because whatever feather edge there may be breaks off so soon as the tool is placed under cutting duty, leaving a flat place along the edge. It would seem, then, that faces which can be ground in the position relative to the stone, shown in Fig. 287 (that is, with the length of the cutting edge lying across the stone), and being upon a tool of shape similar to that shown in the figure, should always be ground with the stone running toward the cutting edge, as shown in the figure at the position denoted by G. This is the case, providing that the stone runs very true and contains no soft or hard spots of sufficient prominence to cause the cutting edge to catch, which would, as already stated, render the operation dangerous. These unfavorable con- ditions, however, are always more or less existent, under average conditions and to such an extent as to forbid the holding of the tool to the stone with the amount of press- ure necessary to remove such a quantity of metal, as is necessary in the earlier stages of the grinding operation. Furthermore, if the edge of the tool does catch in the stone, the damage to that edge, by being ground away, is very serious and entails a great deal of extra grinding to repair it, and at the same time incurs a rapid using-up of the tool. Another consideration is that it is much easier GRINDSTONE AND TOOL GRINDING. 355 to hold the tool steady, under ordinary circumstances, in the position shown at H, than in that shown at G ; and with a bad stone it is altogether impracticable to hold it as at G. Here, however, another consideration occurs, in that the surface of a grindstone is rarely level across the width of the perimeter of the stone, unless the stone has a truing device attached to the frame, which at present is very largely the exception. As a rule the face of the stone is made rounding in its width because there is the most wear in the middle, and it is very undesirable to have the stone hollow across. Suppose, for example, that we have a stone that is hollow, as in Fig. 284, and one that is rounding across the perimeter, as in Fig. 285; then to grind such a tool as is shown in Fig. 2$7, as say a plane blade, we may move it slowly across the width of the stone, and the highest part of the stone will act upon all parts in the width of the blade; but we cannot, by any method, grind such a tool upon the hollow stone without leaving the cutting edge rounding in its length, or else leaving the ground facet rounding in its width or depth, the latter being the case when the cutting edge is held in line with the plane of rotation of the stone. In grinding pointed tools, as centre-punches, scribers, etc., grooves are very apt to be worn in the stone unless the tool be moved back and forth across the stone face, or held at an angle to the plane of rotation. The reason, when truing up a stone by hand, for leaving it rounding across its face is that the middle is more used than the edges, and the wear is, therefore, correspondingly greater in the middle. This causes the stone to gradually wear first flat across and then hollow, necessitating that it be turned up though it may run true. When a stone is uneven across its width, the operator, no matter which side of the stone he is using, holds the length of the cutting edge of the tool at an angle to the width of the stone, as shown in Fig. 288, placing the tool 356 COMPLETE PRACTICAL MACHINIST. in the most level part of the grindstone surface. By doing this he effects two objects : first, he obtains a level spot upon the stone more readily, and secondly, he diminishes the formation of a feather edge. The first is because it is obvious that, in removing a given amount of metal, there will be more abrasion upon the stone in proportion as the operating area of the stone is diminished, hence the \\ork- Fig. 238. r,?an ^rlects the highest part of the stone whereon he can find a suitable surface, and by moving the tool across the face wears down the asperities (while he is roughing out the tool) so as to obtain as smooth a surface as possible for finishing process. If he held the tool still instead of giving it lateral motion, it would grind away in undula- tions or grooves conforming themselves to those on the ibradiug surface of the stone, and the roughing process GRINDSTONE AND TOOL GRINDING. 357 Fig. 289. ivould have but very little effect towards leveling the stone. Referring now to the second advantage named. it will be readily observed that, if he held the length of the cutting edge in a line with the revolutions of the V stone, as in Fig. 289, there would be \ no tendency to leave a feather edge, except at the corner of the edge -where the stone leaves contact with the tool, and this would be of little or no consequence. The question naturally arises, then, why not grind the tool in that position, which would require a very small flat or smooth space in the width of the stone and would avoid the formation of a feather edge. The answer to this is that it would be very difficult to grind the surface of the tool level, as will be perceived from the side view of the operation as shown in Fig. 290, in which A represents Fig. 290. Jf. 358 COMPLETE PRACTICAL MACHINIST. the tool enlarged so as to make the engraving clear. To bring the whole length of the cutting edge to bear upon the stone it is necessary to move the tool from C to D, and from B to E, as denoted by the dotted arcs at D, E; and if during this movement the -tool remains ati Fig. 291. instant too long in either of the positions indicated by the dotted lines, G, H, or at any time during the motion, a hollow spot will be ground upon the tool at the point of contact between the stone and the tool; furthermore the grinding operation is not very accessible to the eye and hence any irregularities are not very easily corrected. GRINDSTONE AND TOOL GRINDING. 359 For these reasons it is impracticable to grind in this posi* tion any cutting edge requiring to be a straight line and having sufficient length to render much motion in the direction of D, E, a necessity. Furthermore it is very difficult to hold a tool steadily in position shown in Fig. 290, and as a consequence no satisfactory result can be attained unless by the aid of a device whereon to rest the hand; such a device is called a rest and is shown in Fig. 291. Now suppose we have a tool of the form shown at C in Fig. 291, requiring to be ground on the faces, A and B; then it is evident that A can only be ground with the body of the steel, C, out of the way of the body of the stone, and hence in the position shown in the figure, in which position the tool may be held and pressed firmly to the stone. It is necessary, however, to rest the hand upon the rest and hold the tool exactly. in the position shown, so that if the tool catches in the stone and is forced from the hand it will not carry the fingers with it, and wound them by jamming either against the stone or the rest, or force them between the two. It would seem advisable to rest the tool upon the rest without the intervention of the hand, but such is not the case, because the operator would not have sufficient control over the tool and it would almost assuredly catch in the stone. By interposing the hand between the tool and the rest, the sense of feeling is brought into play, guiding the operator just how to hold the tool to prevent its catching in the stone and admonish- ing him when the conditions possess any elements of danger, which become instantly known from any difficulty in holding the tool steady against the grip of the stone or from a disposition of the upper edge of the tool, which the stone meets, to turn in towards the stone. CHAPTER XVIII. LINING OR MARKING OUT WORK. WHEN work is got out by means of special machines, or in special jigs, chucks, or appliances, it is generally unnecessary to denote its shape or dimensions by lines. But in large work, such as marine engine work, there are rarely a sufficient number made of precisely one pattern to make it pay to get these special machine tools or appli- ances, hence the work requires to be marked out by lines. So likewise in the case of repairs for all save the small class of machines, such as sewing machines, the work re- quires to be lined or marked out because the original di- mensions must be varied to accommodate the wear of the parts. In the general machine shop the lining out of work forms an important part of the manipulation. In the case of a very simple piece, such as say a square bar, tho lining maybe dispensed with because the lineal measuring rule will demonstrate whether the work is large enough to permit of being cut to the required dimensions. But in irregular shaped bodies it is necessary to mark out the work by lines which serve to set the work true on the machine tools, and to denote the dimensions to which the work should be cut to reduce it to its required form. In giving examples of the processes of lining out work, it has been thought best to let them be of the various parts of an engine, and with this view each part of a simple engine that could be utilized to represent a certain class of work has been selected. 360 LINING OR MARKING OUT WORK. 361 First, however, let it be noted that while the principles Applied in marking or lining out are the same as those involved in mechanical drawing, yet the application is en- tirely different. The draughtsman may obtain his centres aud lines for one view or side of a piece by projecting those from another view or side of the work, whereas in mark- ing out the work the lines must be transferred from one side of it to the other ; or, in many cases, the lines on one side may be entirely different from those on the other, and yet require to be definitely located with reference to the same. The lining out of work requires also to be more accu- rately performed than do the Hues on a drawing, because the variation to an amount of the thickness of a line may involve the spoiling of a piece of work or entail a great deal of extra labor in fitting the parts together. Sup- pose, for example, a block and a strap requiring to be fitted together are marked by lines: the block being marked the thickness of the line too large, and the strap the thickness of the line too narrow. When the work comes to be fitted there will be the thickness of the two lines to file away to make the strap fit to the block. Furthermore, unless lining out or marking out work by lines be very accurately performed, an element of uncer- tainty is engendered, and the machine operators, instead of cutting away the surface metal to split the line, will leave the lines in as evidence that they have not removed too much metal, and as a result the filling operations are again increased. A marker-out, as the operative is termed, should not only be one capable of great exactitude in his measure- ments, but should also be an expert workman at the lathe, vise, planing machine, and drilling machine ; because it is by his lines that the work is chucked, and hence he should know the very best method of chucking or holding the work in each of the machines. Furthermore a line over 31 36$ COMPLETE PRACTICAL MACHINIST. and above those necessary to define "the outline of the work is often necessary for use as an assistance and guide in chucking it. Upon the truth of this lining, in many cases, will the truth of the finished work depend, and even in those instances where the method of chucking will correct any inaccuracy in the marking-out, the use- fulness of the latter is almost entirely destroyed, because the lines will become entirely removed on one side, and left fully in on the other side of the work. If, however, the marking-out is performed reasonably true, one of its main elements of usefulness consists in that it denotes if there is sufficient excess of metal upon the piece of work to permit of its being cleaned up all over. But if there is any one part of the work scant of metal, as is sometimes the case in forgings of unusual and irregular form, the marking-out requires to be very true, and may be made to just save a piece of work that otherwise would have been spoiled. By accommodating the marking to some spot or place in the work, which will only come up to the full size by throwing the whole of the rest of the lines towards the opposite side of the work, a costly piece of forging may be saved from the scrap heap. And again, in castings where the surface appears spongy, showing the presence of air holes beneath the surface, or in forgings where the Bin-face may indicate that a weld is not perfect upon one bide, the whole of the marking-oil I should be performed with a view to take off as much metal as possible on the faulty side. In other work there may be a part very difficult to turn or plane on account of the conformation of the job; in which case the marker-out, foreseeing such to be the case, will so place the lines as to give as little to come off that particular place as possible, disregarding the excessive heavy cut or amount of metal which it may be necessary to cut off other and more accessible parts of the work. There are many other considerations, whicl? need not be here enumerated, all tending to show that a LINING OR MARKING OUT WORK. 363 marker-out should be a master hand at the various branches of his business, and possess much judgment and experience. TO MARK AN ELLIPSE. Draw the line A B, Fig. 292, equal to the required length of the ellipse. Bisect it by the line C D, which must stand ut a right angle to it, be equal in length to the required width of the ellipse, and extend an equal distance on each side of it. With a radius of one-half the re- quired length of the ellipse mark from C (or D) as a centre the arc F H G, and at the points of intersection of this arc with the line A B (that is at F and G) drive in two pins. Drive in a pin at C and pass a piece of fine Fig. 292. twine around the pins at A F, G, and C, and tie it tight enough to prevent any slackness. Remove the pin at C (which is only employed for con- venience in tying the twine to its proper length without being under tension or having any slack). Take a pencil : move it outwards from the pins F G until the twine is drawn straight, then sweep it around and its point will describe an ellipse. In the Fig. the pencil is shown at P, the position of the twine when the pencil is at that point being denoted by the dotted lines. 364 COMPLETE PRACTICAL MACHINIST. The pencil must be held vertical while tracing, otherwise the figure will not be true. To assist this a piece of wood may be laid and slid on the surface, on which the ellipse is traced, and the pencil held against the piece of wood. TO FIND POINTS THROUGH WHICH THE CURVE OF AN ELLIPSE MAY BE DRAWN. Let A B, CD, Fig. 293, be the respective diameters of the curve: mark the parallelogram L M N O meeting the ends of the axes as at A B, C D. Divide A L, A N, S M, and B O into any number of equal parts, and number them as in the Figure. Divide A S and D S into four equal parts : numbering them from the ends to- wards the centre. From the points of division in A L and B M draw lines to the point C, and from the points of division in B O and A N draw lines to the point D. N D O From the point D draw lines passing through the points 1, 2, 3 in A S to intersect the lines 1, 2, 3 drawn from the points of division on A L ; also from point D through D S to intersect the lines from B M. These points of inter- section are points in the curve. From C, through the divisions 1, 2, 3 on S A and S B, draw lines to intersect lines 1, 2, 3 drawn from A N and B O: the points of intersection being points through which the other half of the curve may be drawn. LINI^ 7 G OR MARKING OUT WORK. 365 The tools employed by the marker-out are as follows : Fur plugging holes so that compass points may be sup- ported withiu the hole, disks of lead such as are shown in Figures 294 and 295 are employed. They may be stretched larger or compressed smaller in diameter to suit any required size of hole, by a few blows with the hand -hammer, and the lead will conform itself to the uneven shape of the hole, and will therefore hold fast and not be liable to move ; and, furthermore, a few such blows will deface any lines which may have been made upon the face of the lead in service upon a previous piece of work. Again it may be necessary to first mark a centre line, arid subsequently other lines ; and then drawing a wet finger across the old lines on the lead will dull them, while the newly made ones will be bright, and thus remain distinct. For holes that have been trued out, similarly shaped pieces of sheet brass may be used, the form shown in Fig. 295 being for the larger, and that shown in Fig. Fig. 294. Fig. 295. 294 for the smaller sized holes ; these brass pieces may be filled up very true, and have a centrepunch mark in their exact centre, thus obviating the necessity of finding the centre at each time of using. For use on holes of comparatively large dimensions, 31 - 366 COMPLETE PRACTICAL MACHINIST. that is to say, above 4 inches in diameter, the centre piece shown in Fig. 296 is very convenient. A represents a piece of wood, and B, a small piece of tin or sheet iron, having its corners bent up so that they may be driven into the wood and thus made fast in position to receive the Fig. 296. Fig. 297. centre. Such a centre is very easily and readily made, and may be used on rough or finished work. If the surface of the work upon which either of these centres is used is flat, the ends of the centres must of course be also flat; and in the case of the last de- scribed, a piece of paper, leather, or other material may be inserted in one end to make up any small deficiency in the size. The centrepunch used for marking-out should be as shown in Fig. 297, the object of making its diameter so small toward the point being that it shall not obstruct a clear view of the line. A heavier centrepunch may of course be employed to in- crease the size of the centrepunch marks when the same is necessary. The hammer should also be a small one, weighing about one-quarter of a pound, with a ball face to efface any centrepunch marks erroneously marked or to be dispensed with, an ordinary hammer being employed to perform any necessary operation other than the simple marking-out. LINING OR MARKING OUT WORK. 367 TO DIVIDE A STRAIGHT LINE INTO TWO EQUAL PARTS. From each end of the line we describe arcs of circles, as at F in Fig. 298, adjusting the compasses so that the two arcs meet at the given line, as shown in the figure. Fig. 298. B ? then resting the compass points at the . coincidence of the arcs r \ F, and describing the arcs B C, the latter will cut the ends of the line, as shown in the figure. TO DIVIDE A STRAIGHT LINE INTO A NUMBER OF EQUIDISTANT POINTS. Let A B, in Fig. 299, represent a line to be divided into 10 equal divisions. With a pair of compasses set Fig. 299. AC DJSF-GJJJTJ'XJErJl L_i_j__i_.A y t f ( ( > / \ \ ( ! ) A V S Jt f) I 3 M N V V as near as may be to ^ the length of the line measured upon a finely divided rule, and starting from the end A of the line step off on the line, and mark above the line the arcs C D E F G. From B step off and mark the arcs H I J K L, and if the compasses are correctly set, G and L will join at their point of coincidence with the line. If not, mark a point as shown in the figure, upon the line and midway between G and L. Since G and L overlap each other the compass points are too far apart, hence they must be corrected, which may best be done when the error is a very fine one by oilstoning them on the outside. With the corrected compasses and from the dot as a centre, step off upon the line divisions P O R. From the end A of the line step off divisions S T, and midway between S and T upon the line mark another dot, 368 COMPLETE PRACTICAL MACHINIST. and these two dots will be correct points of division, not- withstanding that the compass points are shown in both cases to be incorrectly set. The want of coincidence of T R, which do not meet at their point of coincidence with the line, shows the compass points to be too near together, hence in this case those points must be corrected by oil- stoning them on the inside. This being done from the dot at G L as a centre, step off on the line the divisions in M N O and mark the arcs, then from the end B of the line mark off V U, and midway between O U is another point of division. The error shown to exist in the compass point being again corrected we may from these four points mark off the intermediate ones. By this method the division may be proceeded with while correcting the com- pass points. If, however, the number of divisions is an odd one instead of an even one as in this example, the compasses must be stepped from each end of the line as before, and adjusted until the space forming the middle division is equal to the distance at which the compass points are set. But suppose it be required that the points of division vary in regular order as in the case of a piece requiring say 60 holes in a given length, the distance between two given holes being 1.57 inches, and the two next 1 inch, and so on continuously. The total number of holes must in this case be an even one; hence we mark off, by the rules already given, one> half of that total number, making them equidistant all round the circle or circumference, as the case maybe, which points will represent the distance apart of the holes that are widest apart, as the holes, A, B, 0, D, and E, in Fig. 300, amounting in our example to 30 in number. We then set our compasses to the required distance apart of the two holes nearest together; and commencing at A in Fig. 300, we mark the centre for the hole, F, and from the centre of the hole, B, the centre of the hole, G, and LINING OR MARKING OUT WORK. 369 so on, continuing all round the circle, but taking care to mark the new centre in each case in advance of or behind the points, A, B, C, etc., according to the manner in which Fig. 300. < 1 x 1.57. x 1 * $ *i i,9 ty O $ O A B K C D A the first of the holes nearest together was marked. Thus in Fig. 300, the points, F, G, H, and I, are marked to the right, in each case, of the points from which they were struck. Before proceeding to mark out a piece of work, it should be roughly measured so as to ascertain, before having any work done to it, that it will clean up. The square should also be applied to see if it is out of square, and thus to find out if it is necessary to accommodate the marking out to any particular part that may be scant of material (or stock, as it is often termed). The surface of the work should also be examined ; so that, if any part of it is de- fective, the marking off can be performed with a view to remedying the error, whether of excess or defect. Now let us mark off a block, say of 12 inches cube, and we shall find that we must not mark it out all over until one of the faces has been planed up. Suppose, for instance, we mark it out as shown in Fig. 301. The inside lines on faces A and B are the marking-ofF lines. If, then, we cut off the metal to the lines on A, we shall have removed the lines on B, and vice versa; and there is no manner or means of avoiding the difficulty, save as follows: We may mark off one face, and let the block be cut down to the lines, before mark- 370 COMPLETE PRACTICAL MACHINIST. ing the other face; or we may have a surfacing cut taken off one face, and then perform the whole of the marking off at one operation. The latter plan is preferable, be- cause it gives us one true face to work from in marking off, and obviates the necessity of having to prevent the rocking of the work upon the marking-off table by the insertion of wedges, which is otherwise very commonly requisite. It is preferable, then, upon all work easily handled and chucked, and in which the lining off must be performed on more than one face, to surface one face before performing the marking out ; and supposing our block to have one face so surfaced, we will proceed. We first well chalk the surface of the work all round about where we expect the lines to come, which is dose to make the lines show 30 ' 2 ' B J plainly; we then place the work upon the table with the surfaced face downward ; and placing a rule along- side of it, we set the scriber of the surface gauge so as to take off the necessary amount from the top, as shown in Fig. 302 (A being the plated, and mark the line, B, around all four faces of the work. We then turn the work on the plate so that the true face stands perpen- dicularly, setting it true by wedging it, so that a square being placed with the back to the face of the table, and the blade against the surfaced Fig. 303. F I jl C *-JZ * ^~ E ~| A OR MARKING OUT WORK. 371 Fig. 304. face of the work, the latter will stand true with the square blade,, as shown in Fig. 303. A being the marking-off table, B the square, and C the surfaced face of the work. We then (with the scribing block) mark, across the sur- faced face of the work, two lines, 12 inches apart, and of equal distance from the top and bottom faces of the work, as shown in Fig. 304, at A and B. Our next operation is to mark off, on the surfaced face of the work, two more 1 lines, standing at right angles to the lines A and B in the above figure ; so that the surfaced face will have four lines upon it. These last two lines we mark without moving the work, by placing a square with its back rest- ing upon the table, the square blade standing vertically and at the necessary distance from the edge of the block, as shown in Fig. 305, A and B being the lines drawn by the scribing block, and C C the square in position to draw one of the necessary per- pendicular lines, the other, shown at D, being sup- posed to have been marked from the square while it was turned around. Here, then, we have the lines for four of the faces, marked upon a face already sur- | faced to the size, thus dis- posing of five out of the six faces : and since the line for the sixth face stands diametrically opposite to the sur- faced face, the latter has only to be kept down evenly upon the table of the planer to insure the sixth face being cut true ; after which, and when each of the remaining Fig. 305. 1 372 COMPLETE PRACTICAL MACHINIST. four sides is chucked to be operated on, we have a true face to place next to the angle plate, and a true one against which to apply the square to test if the work is held true. Thus we find that the surfaced face of the work, when placed on the face of the marking-off table and on the face of the planer table, becomes a gauge by which (with the aid of the square) all the other faces may be marked or cut true. It is obvious that, had either one of the faces of the work 'been faulty, we might have taken off it as much metal as possible, leaving only sufficient to clean up the face diametrically opposite. It often happens that an ap- parently faulty face shows to more disadvantage by having a cut taken off it; especially is this the case in iron castings, in which there may be more air holes beneath than upon the surface, which defect may be sufficiently serious to spoil the work. It is therefore preferable to take the first or surfacing cut off the defective face, so that the degree of defect may be discovered before even the marking-out is performed. The lines being marked, our next procedure is to make light centrepunch marks at short intervals along them, so that, if the lines become obliterated through handling the work, the centrepunch dots will serve instead. These dots should be marked very true with the lines, otherwise they destroy the truth of the marking ; because the machine operator, in setting the work in the machine, is usually guided by the dots. By this method we may mark off any body whose out- line is composed of straight lines, and whose diametrically opposite faces are parallel, no matter what the length, breadth, and thickness of the body may be. It is not, however, at all times desirable to perform all the marking- out at one operation. Suppose, for example, our work had been a piece of metal 1 foot square and I of an inch thick : were we to face off one of the broad faces before marking' LINING OR MARKING OUT WORK. 373 off, we should find it very difficult to set our work upon the rough edge, and set it true to the square, as shown in Fig. 303; whereas, were we to face off one of the edges first, we have I of an inch only against which to try the square when setting the planed edge perpendicular. In such a case, therefore, it is best not to mark off the edges until the body of the work is cut to the required thick- ness. To mark off a body such as shown at B in Fig. 306, which represents an engine guide bar, one face must either be first trued up. or the mar king-off must be performed at two separate operations. The belter plan is for the marker- off to examine the bar as to size, and have one face planed off. If either face appears defective, it should be the first planed. If the bar appears sound all over, an outside edge face of the bar should be the one to be planed off preparatory to marking-off ; and in setting it to surface it, care should be taken to set it true with the top and bottom faces, if they are parallel to each other ; and if not, to divide whatever difference there may be between them. The bar may then be placed upon the marking-off table in the position shown in Fig. 306, A being the marking-off Fig. 306. plate, B the guide bar, C C pieces of wood to lift the bar off the plate. By means of small thin wedges, the planed face, B, of the bar, is set at a true right angle to the sur- face of the plate, and tested by a square. The next oper- ation is to mark off the top or uppermost face, and the question here arises : Shall it be so marked that there will be an equal amount of metal taken off the top and bottom 32 374- COMPLETE PRACTICAL MACHINIST. faces, or otherwise ? First, then, since the quality of the metal is the best towards the surface, it is a consideration to take off as little as possible, so as to leave a hard wearing surface ; this may appear a small matter, but it is always right to gain every superiority attainable without cost. Therefore, all other things being equal, we should prefer to take as little metal off the top face as would be sufficient to make it true, and should therefore mark it out with that view. Here, however, another consideration arises, which is that the outline of the bottom face is not straight, and cannot therefore be planed lengthways from the centre of the bar to the ends at one chucking, and if such bottom face is to be shaped across its breadth, instead of lengthways, it is a comparatively slow operation, and much time will be saved by so marking off the bar that the bottom will only just true up, so that all the surplus metal will be cut off the top face, which, being done in a larger machine, and lengthways, is a much more rapid operation. There is, however, a method of obtaining both the advantage of taking as little as possible off the top face, and planing the bottom face for the most part length- ways. It is shown in Fig. 307, A being the bar ; the two faces, B B, may be first planed parallel (as required) with the face, C ; the back of the bar may then be planed in two operations from the point, D, to the junction with B at each end. Were this method of procedure employed, it would pay to leave the most metal to come off the hack of the bar ; but there are yet other considerations, which are the facilities in the shop. If the shaping machines are not kept fully occupied, while the planing machines LINING OR MARKING OUT WORK. 375 are always in demand, it will pay (if there are not many bars to be planed) to leave as little as needs be to be taken off the bottom of the bar and the remainder off the top. If, however, many bars are to be planed, the most econom- ical of all methods will be to plane the backs by placing, say 8 of them at a time across the table of the planer, cutting off the ends at the same chucking. Supposing this plan to be adopted, we set the scriber of the marking block just below the lowest part of the surface of the bar, and draw a line along its planed surface, and then another line along each end, to denote the thickness of the parallel parts at each end, making this line longer than is neces- sary, as a guide in setting the bar in the shaper (in case the ends are shaped and not planed). We next mark oft* the length of the bar at the ends, using a square and al- lowing about an equal amount to be taken off each end ; and then, still using the square, we mark a line equidis- tant between the end lines to denote the centre of the length of the bar, which will then present the appearance shown in Fig. 308, the inside line, A A, being for the top Fig. 308. face, the lines, E, for the parallel ends, the lines, B B, for the ends, and the line, D, denoting the middle of the length of the bar. We now turn the bar so that its planed face is uppermost; and, setting a pair of compasses to the required thickness of the middle of the bar, we set one point at the junction of the lines, A and D, mark otf with the other point a half circle, and then (turning the bar over) adjust it upon the table, as shown in Fig. 310, A being the table, and B a block of wood and wedge to adjust the bar, so that, if the scribing block be applied 37(5 COMPLETE PRACTICAL MACHINIST. along the table, the needle or scriber point will mark just fair with the top of the circle at D and the mark, C, at the end of the taper part of the bar (the mark, C, showing the required distance from the end of the bar). Having made the adjustment, we draw the line, E, thus com- pleting the marking of that half of the bar. We next remove the block of wood and wedge to the other end of the bar, and repeat the last operation, when the marking of the bar will be, so far as its outline is concerned, com- plete. It will be observed that we have drawn the lines in each case on the one planed surface of the bar only, and not all around the work. The reason for this is that the planed face is a guide, whereby to chuck the work and ensure its being set true. In the absence of one true face it would be necessary, in marking off the first face, to mark the lines all around the work, which, when planed up, would serve as a guide whereby to set the work during the successive chuckings. Fig. 311. A After the faces and ends are planed up, the holes in the ends may be marked by the compass calipers and com- passes, as shown in Fig. 311, A being the bar, and B B LINING OR MARKING OUT WORK. 377 the compass calipers set to the required distance. At the junction of the marks thus made, we make a light centre- punch mark, and mark off the circles for the holes, first marking a circle of the requisite size and defining its out- line by other light centrepunch marks. We next draw from the same centre a circle smaller in diameter, and define its outline also by small centrepunch marks; after which we take a large centrepunch, and make a deep in- dentation in the centre of the circle, which will appear as shown in Fig. 312. The philosophy of marking the holes in this manner is as follows: If the Fig. 312. outside circle alone is marked, there is nothing to guide the eye during the operation of drilling the holes (in determining whether the drill is cutting the holes true to the marks or not) until the drill has cut a recess nearly approaching the size of the circle marked ; if the drill is not cutting true to the marks, and the drawing chisel is employed, it will often happen that, after the first operation of drawing, the drill may not yet cut quite true to the marks ; and it having entered the metal to its full diameter, there is no longer any guide to determine if the hole is being made true to the circle or not. By introducing the inside circle, however, we are enabled to use the drawing chisel, and therefore to adjust the position of the hole during the ear- lier part of the operation ; so that the hole being cut is made nearly if not quite true before the cutting ap- proaches the outer circle, which shows the full size of the hole. If, on nearly attaining its full diameter, the outer circle shows it to be a little out of truth, the correction is easily made. It is furthermore muoh more easy to draw the drill when it has only entered the metal to, say, half its diameter than when it has entered to nearly its full diameter 32" 878 COMPLETE PRACTICAL MACHINIST. The object of making a large centrepuuch mark in thn centre is to guide the centre of the drill, and to enable the operator to readily perceive if the work is so set that the point of the drill stands directly over the centrepunch mark. This is of great importance in holes of any size whatever, but more especially in those of small diameter, say. for instance, 4 inch, because it is impracticable to de- scribe circles of so small a diameter whereby to adjust the drilling; and in these cases, if the drill runs out at all, there is but little practical remedy. The centrepunch marks for such holes should therefore be made quite deep, so that the point of the drill will be well guided and steadied from the moment it comes into contact with the metal, in which case it is not likely to run to one side at sill. If a motion or guide bar requires to have one corner rounded off, as it should have to prevent its leaving a square corner on the guide block, which would weaken the flange of the latter, the corner cannot be marked off, but a gauge should be made as shown in Figs. 313 and 314, Fig. 314. A in Fig. 313 being a piece of sheet-iron, say ^ inch thick, with the lines, B and C, and the quarter circle, D, marked upon its surface. The metal, G, is then cut away, and the edges carefully filed to the lines, thus form- ing the gauge, A, which is shown upon the bar, F, in the position in which it is applied when in use. It is obvious that such a gauge will scarcely suffice to get up a very true round corner; this, however, is accomplished by leaving LJNING OR MARKING OUT WORK. 379 the corner of the work a little full to the gauge and then filing it up to the piece of work fitting against it. TO MARK OFF THE DISTANCE BETWEEN THE CENTRES OF TWO HUBS OF UNEQUAL HEIGHT. When the heights of two hubs are unequal, as shown in Fig. 315, the distance required being that from A to B, we must make the necessary allowance (in the distance at Fig. 315. which we set the compass or trammel points) for the dif- ference in height of the surfaces upon which our circles are to be marked, from the body of the lever or arm. If Fig. 316. (7. Divide a straight line into two equal parts, to, 367. Dog or carrier for lathe work, a simple form of, 116, 117. Dog, the clamp, 119. Dogs, chuck, 135. Double eye, to line out a, 383-389. Double screwthread, to cut, 102-104. Drifts, 325-329. Drifts, cutting, 326. Drift, using the, 327-329. Drill and countersink, combined, for cen- tre-drilling, 125. Drill, Farmer lathe, 204. Drill, flat, for enlarging and truing out holes, 168-171. Drill holder, 170, 171. Prill, tit, 202. Drilling hard metals, 205, 206. Drilling in the lathe, 164-171. INDEX. 435 Drills, common, used as countersinks. 213. Drills, countersink, 212-214. Drills, feeding, 202-205. Drills, flat, 201, ?02. Drills, flat, defects in, 20', 202. Drills ground by hand, testing for angle, 199, 200. Drills, machine made, shanks of, 204. Drills, pin, 211,212. Drills, slotting or key way, 206, 211. Drills, temper for, 204. Drills, twist, 196-201. Driver for lathe work, Clements', 116, 118. Hccentric, chucking an, 136-138. Kccentric, marking out an, 389-396. Kccentrics, turning, 136. Ellipse, to find the points through which the curve of may l>e drawn, 364. Ellipse, to mark out an, 363, 364. Emery cloth and paper, 128-130. Emery wheel for grinding reamers, 172. Emery wheel, use of with milling cutters, 345, 346. Engine guide bar, to mark out an, 373- 378. English grindstones, 347. English or Whitworth standard for screw threads, 244. English standard taps, flutes for, 246, 247. Examination of work beibie marking out, 369. Farmer lathe drill, 2 H. Feed and speed, cutting. 64-70. Feeding drills, 202-205 Feeds and speeds, culling, tables of, 69, 70. File, holding a, 270. File, selecting a, 269. Files and filing, 269-280. Filing out templates. 272-280. Finishing lathe work, 127, 128. Fitting brasses to their boxes, 284, 285. Fitting connecting rods. 314-324. Fitting cylinders, 288-297. Fitting link motions, 285-288. Flanges, fitting to boilers or flanges, 313. Flat drill, experiments with, 204. Flat drill for enlarging and truing out holes, 168-171. Flat drill, grinding, 202. Flat drill, increasing the keenness of by means of an ellipse, 202. Flat drills, 201,202. Flute of a tap, spiral, 241. Flute of a tap, volute, 241. Flutes for small taps, 243. Force pumps, 425, 426. Forging and hardening lathe tools, 25. Forging tools, 220-222. Four-flute tap, 246, 247. Forms, special, of lathe tools, 54, 55. France, pitches of threads of scivws use in, 102. Franklin Institute, standard for screw threads adopted by, 243. Front tool," 2fi, 28. Front tool for biass work, 50-53. Ras taps, the taper of, 241, 242. Gauge for grinding and setting screw tools, 92, 93. Gauge for testing the angles for thread- ing tools, 90. 91, 92. Gauze joints for high temperatures, 313. iirder. wear of, 232. 5 rain of properly forged tool steel, 226. Jraver, the, 154-159. Graver, the application of, 155-lnT. Grinding, holding a tool in, 352, 353. Grinding pointed tools. 355. Grinding reamers, 172-174. Grindstone and tool grinding, 347-359. Grindstone for engravers' plates, 349. Grindstone for tool grinding, 349. Grindstone of uneven surface, using a, 355. Grindstone, the face of a, for flnt surfaces, 352. Grindstone, truing device for, 350, 351. Grindstones, different varieties of, and their qualities, 347, 34*.. Grindstones, fitting with traversing rests, 347. Grindstones should be run true, 349. Grindstones, the surfaces of, 348. Grindstones, use of, 347. Grooving tool, 61-63. Grooving tool for brass work, 45. Grooving tool for wrought-iron or steel. 44-46. Grooving tools. 44-47. Gun metal, 237. Half-round bits, 166-168. Hand chasing, 104-107. Hand stocks, dies for use in, 251-255. Hand taps, 248, 249. Hand tools, 25. Hand turning, 151-163. Hand turning brass work, 159, 160. Hard metals, drilling, 205, 206. Hard saw blades, to cut, 304. Hardening, 227. Hardening American chrome steel, 226. Hardening and tempering tools, 222-227. Hardening cast-steel, 228. Hardening lathe tools, 25. Hardening springs, 227-229. Hardening taps, 244-246. Hardness in tools, sacrificing by over- heating. 225. Heat, proper, in forging taps, 238, 239. Heel tool, 157-159. Heel tool, hardening, 158. Height of the cutting edge of a tool, re- lation of, to the work, 40-42. Holders, boring tool, 82, 83 Holders, tools, 55-63. Holes, to enlarge, and true out, 168. Horton two-jawed chuck 131 Hubs of unequal height, to i~iark <-fl' the distance between the centres of, two, 379-381. Huron grindstones, 347. 436 INDEX. Independence grindstones, 347. Iron and steel, swelled by hardening, 228. Tron, case hardening, 229,230. Iron, side tools for, 47-50. Iron, wrought and cast, cutting speeds and feeds for, 69, 70. Joint, rust, 313. Joint, steam and water, 313. Joint, the ground or scraped, the best. 313. Joints, gauze for high temperature, 313. Joints of canvas or duck coated with red lead, 313. Joints, ordinary, 313. Joints, red lead, 313. Joints, rubber, 313. Journal boxes, brass for, 237. Journals, fast-running, Babbitt metal for, 237. Keys, reversed. 329-331. Key way. marking out a, 402. Keyway or slotting drills, 206-211. Lathe chucks, 131-135. Lathe-cutting tools, classification of, 25. Lathe dogs, carriers or drivers, 116-119. Lathe, hand expert, 25. Lathe, the importance of, 25. Lathe tools, cutting surfaces of, 84. Lathe tools, forging and hardening, 25. Lathe tools, special forms of, 54, 55. Lathe work, boring tools for, 71-83. Lathe work, centring, 122-127. Lathe work, feed and speed in, 64, 65. Lathe work, finishing, 1^7, 128. Lathes and planing machines, cutting tools for, 25-63. Leaky plugs, to rivet to their cocks, 304- 308. Left hand thread, wheels necessary to cut, 102. Lever arms, boring, 144, 145. Line, a straight, to divide into a number of equidistant points, 3fi7. Line-shafting, setting in line, 331-337. Line, straight, to divide into two equal parts, 367. Lining or marking out work, 360-410. Lining or marking out work, tools em- ployed in, 365, 366. Lining out a double eye, 383-339. Lining out connecting rod, 390-408. Lining out work, accuracy required in, 361. Lining out work, importance of, 360. Lining up brasses, 324. Link motions, fitting, 285-288. Links or levers, boring. 144, 145. Liverpool grindstones, 347. Long continuous cuts, tool for, 33. Machine steel, hardening, 228. Machine tools are cutting wedges, 29. Machine using a boring bar should not stop, while the finishing cut is being taken, 180, 181. Mandrils or arbors, 120-122. Mark off the distance between the centres of two hubs of unequal height, to, 379- 381. .Mark out an ellipse, 363, 364. Marker out, qualifications necessary in a, 361-363. Marker out, tools employed by the, 365, 366. Marking holes at a right angle, 381-383. Marking off a crosshead, 381. Marking or lining out work, 360-410. Marking out a cone pulley, 408-410. Marking out a cubical block, 369-373. Marking out a keyway, 402. Marking out an eccentric, 389-396. Marking out an engine guide-bar, 373- 378. Marking out a rod end, 397. Measuring work before marking out, 369. Mailing grindstones, 347. Metals, hard, drilling, 205, 206. Metals to be cut, influence of, on shape of to. 1,26. Metal surfaces, wear of. 230, 231. Milling bar and cutters, 330-346. Milling cutter, 339-316. Milling cutters, email M/e, 344. Milling machine, imp' rtance of, 338. Milling machines and milling tools, 338- 346. Milling machines, the cutters of, 64. Milling tools and milling machines, M8- 346. Mixture of metals, 237. Morse Twist-diill Co., thread upon Iho taps of, 344. Mnsh et's "special tool steel," 220. New Castle grindstones. 347. Nova Scotia grindstones, 347. Oblong holes, drilling, 206. Ohio grindstones. 347. Oil-hole for a strap for a connecting or a side rod, 322. Overheating tools in hardening, 225. Panelling and dovetailing machine, Boult's, 210. Pening, 282-284. Pin drill, employing as flat-bottomed countersink drill, 212. Pin drills, 211,212. Pin drills, tempering, 211, 212. Pitch of screw, a coarse tool for cutting, 84, 85. Pitch of screws, to calculate the changed gear wheels for, 94-102. Piston, boring, to ret eive the piston rod, 145. Piston pumps, 426-4.-H. Piston ring, expanding chuck fur hold- inn, 150. Piston rings, cast-iron, wear of, 230. Piston rings, inside diameter or bore of, 147. Piston rings, turning, 147. Pistons nnd rods, turning, H5, 146. INDEX. 437 Piston rings, 1 40-150. Planer tool, a, 42, 43. Planing machines, cutting speed of, 64. Planing machines, cutting tools for, 25- 63. Plug tap, 241. Plugs, leaky, to rivet to their cocks, 304- 308. Points through which the curve of an ellipse may be drawn, to find, 364. Pratt & Whitney tap, 248, 249. Principles affecting the shape of cutting tools, 26, 27. Pulley, cone, to mark out a, 4^8-410. Pulleys, wheels, etc., to calculate the speed of, 411-413. Pumps, 423-4;H. Rake, bottom and side of a tool, what de- pendent on, 40. Rake, effect of having little in a tool, 30, 31. Rake, front and side, a tool with, 34, 35. Rake front in a tool, effect of, 34. Rake in cutting tools, 27-29. Rake of a tool, and diameter of work, relation of, 40. Rake, side and front, in a tool, 33. Rake, side, in a tool, 31-3:3. Rake, side, in a to >1, effect of, 34. Rake, top, effect of a great, in a tool, 29, 30. Rake, top, in a tool, 35. Rake, top, in a tool, effect of, 31. Reamer, adjustable, for small work, 175, 176, 177. Reamer, considerations in determining the form of, 171, 172 Reamer, method of grinding. 172-174. Reamer, standard, great advantage of, 174. Reamer, the, to maintain to standard diameter, 174. Reamers, 171-177. Reamers, adjustable, 174, 175, 176, 177. Reamers and bits, 171. Reamers, shell, 176, 177. Re-centring work which has already been turned, 126,127. Reciprocating and revolving surfaces, wear in, 234, 235. Red lead joints, 313. Reversed keys, 329-331. Riveting work by shrinking it, 308-312. Rivet leaky plugs to their cocks, to, 304- 308. Rod end, marking out a, 397. Rotary engines, difficulty of the success of, on account of the inequality of wear in side or disc surfaces, 233. Round-nosed tools, 36, 37. Round-nosed tools, cutting edge on, 36. Rubber joints, 313. Roughing-out brass work, tool for, 159. 160. Roughing-out hand-turned work, 154. Ronghing-nut, tool for, 33. Russell Tool Co.'s drill chuck, 13 i. Rust joint, 313. 37* Saw blades, hard to cut, 304. Scale in hardened steel, 226. Scraped surfaces, 297-301. Scraper, best form of, 301. Scrapers and scraping, 280, 281. Scrapers for brass work, 160-163. Screw-cutting gear, compound or double, 97. Screw-cutting tools, 84-115. Screw thread, a double, to cut, 102-104. Screw threa/1, the United States standard, 88, 89, 90. Screw thread, the Whitworth, 88, 89. Screw threads in use in the United States, the shapes of, 87-89. Screw threads, standards for, 243, 244. Screw threads used in France, pitches of, 102. Screw, to cut, by hand in the lathe, 104- 107. Screw tools, gauge for grinding and set- ting, P2. Screws, to calculate the clnngo gear wheels to cut the pitch of threads for, 94-102. Scribing block, 268. Sellers, Wm. & Co., experiments with a flat drill, 201. Setting line shafting in line, 331-337. Shafting, line, setting in line, 331-337. Shape of cutting tools, 26. Shape of work, importance of, in harden- ing, 227. Shaping machines, tool holders for, 60-62. Sheet-iron, cutting out holes of a large diameter in, 217. Shell reamers, 176, 177. Shrinking, riveting work by, 308-312. Side-rest tools, 25. Side-rest tools, classification of, 26. Side tool, 26. Side tool for brass work, 53, 54. Side tool for small work, 48, 49. Side tools for iron, 47-50. Side tools, left-handed and r'ght-handed, 48. Sizing die for finishing taps, 242, 24:5. Skin of iron or brass c;istings. and iron or steel forgings, hardness of, 342. Slide valve, considerations in setting, 414. Slide valve, to set a, 414-422. Slide valves, cast-iron, wear of, 230. Slot drill, application of the principles of the action of, 210. Slotting drill, labor saved by, 210. Slotting drills, tempering, 209. Slotting machine tools, 191-195. Slotting or key way drills, 206-211. Soldering liquid, 237. Solders, 237. Speed and feed, cutting, 64-70. Speeds and feeds, cutting, tables of, 69, 70. Speed of wheels, pulleys, etc., to calcu- late, 411-413. Spring tool, 26. Spring tool, for finishing sweeps, curves, and round or hollow corners, 46! Spring tool, the top face of a, 47. 438 INDEX. Springs, hardening, 227-229. Springs, the steel for, 227, 223. Spur centre, the wood-turners', 119, 120. Square-nosed tool, setting and feeding, 38. Square-nosed tools, 37-43. Square-nosed tools, what used upon, 37, 38. Square, the, 267. Steam and water joints, 313. Steam valves and cylinder posts, marking out, 406-408. Steadying device and tool holdor. 59. Steel, cutting speeds and feeds for, 69. Steel for taps, 238. Steel, grooving tool for, 44-46. Steel, hardening and tempering, 222. Steel, tool, 25, 219, 22(1. Stock and cutter, in cutting out holes of a large diameter in sheet-iron, 216, 217. Straight line, to divide, into two equal parts, 267. Straight line, a. to divide into a number of equidistant points, 367. Strain on a tool, 29. Strain upon a tool in cutting, 30. Straw color in tempering tools, 225. Suction pumps, 423-425. Surface plate, to make a, 301-304. Surfaces, scraped, 297-301. Sweetlaud chuck, the, 133, 134. Tables of cutting speeds and feeds, 69,70. Tap, a three-flute, 246, 247. Tap, finishing tlie thread of, by passing through a sizing die, 212, 243. Tap, hand and m >chine-made, turning the taper of, 241, 242. Tap, taper, 241 Tap, the nut, 240. Tap, the plain part of a, 242. Taper, plug, 241. Taper tap, 241. Taper in taps, 241, 242. Taper tap, the proper taper for, 239. Taps and dies, 238-255. Taps for holes, requiring, to be exact in diameter, 241. Taps tor holes to be tapped deeply, 242. Taps for ordinary work. 241. Taps for use in machines, threads of, 240, 241 . Taps, forging, 238. Taps, gas, the toper of, 241, 242. Taps, heating, for hardening, 244-246. Taps, heating in f< Tging, 238. Taps, small, flute for, 243. Taps, standard, screw thread for, 243, 244. Taps, steel for, 238. Taps, taper in the diameter of the bottom of the thread, 241 . Taps, threads of, 239, 240. Taps, threads of, finishing, 239. Taps, three-fluted and four-fluted, 246, 247, 248. Taps with thread on small end of taper, 242. Temper for drills, 204. Tempering and hardening tools, 222-227. Tempering a tool at or near the cutting edge only, 223. Tempering cutte' s, 217, 218. Tempering pin drills, 211, 212. Tempering slotting drills, 209. Templates, filing out, 272-28 >. Thread, internal screw, tool for cutting, 87. Thread, left-hand, wheels necessary to out, 102. Threading tools, gauge for testing the angles of, 90, 91, 92. Threads of screws, cutting small and thick, 84, 85. Threads of screws, coarse, cutting, 84, 85. Threads of screws in use in the United States, shapes of, 87-89. Threads of taps, 239, 2W. Threads of taps, finishing, 239. Threads of taps of small size, finishing, 239. Threads on wrought-iron or steel, tool for cutting, 86. Threads, outside V, in brass work, to <>1 for cutting. 80. Threads, V, in iron, tool for cutting, 86. Tit drill, 202. Tool feed, rake of, 40. Tool for roughing out and long-continu- ous cuts, 33. Tool grinding and grindstone, 347-359. Tool hardening and tempering, 222-227. Tool holder and steadying device, 59. Tool holder for planing machine tools, 61-63. Tool holder, Woodbridge's, 57-59. Tool holders, 55-63. Tool holders for a shaping machine, 60- 62. Tool steel, 25, 219, 220. Tool steel, Mushet's, 220. Tool with a combination < f front and side rake, 34. Tools and tool holders, Woodbridge's, 57-59. Tools, angles of, 39 Tools, cutting, for lathes and planing machines, 25-63. Tools employed by the marker out, 365, 366. Tools for cutting various screw threads, 80, 87. Tools, forging, 220-222. Tools for use in slotting machines, classi- fication of, 181. Tools, round-nosed, 36, 37. Tools, screw-cutting, 84-115. Tools, square-nosed, 37^13. Top rake, application of, to a boring tool, relation to the strain, 74, 75. Turning cranks, 140. Turning eccentrics, 136. Turning, hand, 151-163. Turning pistons or rods, 145, 146. Twist-drills, 196-201. Twist-drills, cutting edges of, 197-200. United States standard for screw threads, 243. INDEX. '-39 United States standard screw thread, 88, 89, 90. United States, the screw threads in use in, 87-89. Valves, brass for, 237. Vise clamps, 280, 281. Vise work, 256-313. Water and ste'im joints, 313. Wear arising from motion in one contin- uous direction, 230. Wear greater in revolving than in recip- rocating surfaces, 234, 235. Wear, inequality of, in revolving side or disc surfaces, 233. Wear of metsil surfaces, 230-230. Wheels, pulleys, etc., to calculate the speed of, 411-413. Whitworth or English standard for screw thread, 244. Whitworth or English standard tapj,_ flutes for, 246, 247. Whitworth screw thread, 88, 89. Whitwoi th, Sir Joseph, lathes of, 41. Whitworth stocks and dies, 253. Whitwoi th taps, flutes and teeth, 218, 249. Wickersly grindstones, 347. Woodbridge's patent tool and tool holder, 57-59. Wrought-iron, case-hardening, 229, 230. Wrought- iron, cutting speeds and feeds, 69. Wrought-iron, grooving tool for, 44-46. Wrought-iron, screw-cutting tools for, 84. Yellow brass, 237. Yellow brass for castings, 237. Joshua Rose, M. E., P. O. Box 3306, New York City, Author of l ' The Complete Practical Machinist, " ' ' The Pat- tern Maker 1 s Assistant" "The Slide Valve" "Me- chanical Drawing Self- Taught" "Modern Machine Shop Practice. ' ' Gives mechanical advice upon The purchase of Machine Tools, The selection of Machinery, The fitting out of Workshops, The value of Inventions, and prepares Catalogues and Descriptions of Machin- ery and of New Inventions. The Sweetland Chuck Universal and Independent. A first-class tool thoroughly well made. SWEETLAND & CO., NEW HAVEN, CONNECTICUT. The Russell Tool Co.'s DRILL CHUCK Will drive work to be turned without any slip, without the use of a wrench, and with- out being strained, Operates easily, is thoroughly well made, Jaws of best hardened steel, Warranted to give satisfaction and be durable, THE RUSSELL TOOL CO., 96^ Summer Street. Boston, Mass. F. E. REED, Manufacturer of Light Machinists' Tools, 54 Hermon Street, Worcester, Mass., TJ. S. .A.. FOOT POWER LATHES A SPECIALTY. OF practical and {Scientific PUBLISHED BY HENRY CAREY BAIRD & Co, INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 Walnut Street, Philadelphia. Jt5&- Any of the Books comprised in this Catalogue will he sent by mail, free of postage, to any address in the world, at the publication prices, 4=- A Descriptive Catalogue, 96 pages, 8vo., will be sent free and free of postage, to any one in any part of the world, who will furnish his address, JSP Where not otherwise stated, all of the Books in this Catalogue are hound in muslin. 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By R. S. CRISTIANI, Con- sulting Chemist and Perfumer, Philadelphia. 8vo. . . #5' CUPPER. The Universal Stair-Builder : Being a new Treatise on the Construction of Stair-Cases and Hand- Rails; showing Plans of the various forms of Stairs, method of Placing the Risers in the Cylinders, general method of describing the Face Moulds for a Hand-Rail, and an expeditious method of Squaring the Rail. Useful also to Stonemasons constructing Stone Stairs and Hand-Rails ; with a new method of Sawing the Twist Part of any Hand-Rail square from the face of the plank, and to a parallel width. Also, a new method of forming the Easings of the Rail by a gauge ; preceded by some necessary Problems in Practical Geometry, with the Sections of Prismatic Solids. Illustrated by 29 plates. By R. A. CUPPER, Architect, author of "The Practical Stair-Builder's Guide." Third Edition. Large 4to. DAVIDSON. 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