THE YOUNG MECHANIC CONTAINING (' DIRECTIONS FOR THE USE OF ALL KINDS OF TOOLS, >JD FOR THE CONSTRUCTION OF STEAM ENGINES AND MECHANICAL MODELS, THE ART OF TURNING IN WOOD AND METAL. AUTHOR JF "THE LATHE AND ITS USES" ' THE AMATEUR MECHANIC'S WORKSHOP," &c. FROM THE ENGLISH EDITION, WITH CORRECTIONS, G. P. PUTNAM'S SONS NEW YORK LONDON 27 WEST TWENTY-THIRD ST. 24 BEDFORD ST., STRAND nithtrbothtr |)ress 1896 CC10 Entered according to Act of Congress, in the year 1871, by G. P. PUTNAM & SONS, in the Office of the Librarian of Congress at -Washington. \G O L y INTRODUCTION TO THE AMERICAN EDITION, IN presenting the American edition of this little work to the public, we believe we are supplying a want that has long been felt by the Young Mechanics of this country, and many others who desire to become versed in the practical use of tools. We know of no other book published in this country or England, in which the method of using tools is so clearly explained ; and although written more especially for boys and beginners, it contains much information that will be of great value to the practical mechanic. The author is evidently thoroughly acquainted with his subject, and understands how to communicate his ideas in a simple and concise manner. The first six chapters are devoted to the description of Tools for working wood and the manner of using them, beginning with the simplest operations, requiring but few tools, and gradually leading on to the more difiicult, giving examples of all the methods of joining and finishing work that are in common use among good workmen, and in this connection we would like to call attention to the small number of tools the author requires for performing all these different operations, the idea among amateurs and boys generally being, that if you only have tools enough you can make anything. This is not so, and if the begin- ner will follow the advice of the author, and buy a few good tools, and learn the use of them thoroughly, and gradually add to his stock as his knowledge of their use increases, he will find it greatly to his advantage. The next five chapters relate to the lathe, and the art of turn- ing. The author follows the same plan as in the first part of the book, and gives more practical information in these few pages than we have seen in any other book on the subject, most of them being written apparently for finished mechanics, and not for beginners. The Art of Turning as an amusement, is beginning to attract considerable attention in this country, but not so much n INTRODUCTION. as it deserves and would obtain, if it were more generally known how many beautiful and useful articles can be produced in the lathe. The expense of the necessary tools has deterred many from attempting to learn this branch of mechanics ; but we believe if any one has the time and patience to devote to the work, they will never have occasion to regret the money spent for thia purpose. The last four chapters contain practical instruction in model- making and working in metal. This part of the book we would particularly recommend to inventors who desire to make their own models, as it contains information in regard to files, drills, and the various small tools used on metal, and also directions for lay- ing out work, which are invaluable to a novice in such operations, and will save him much time and trouble. As this book was originally published in London, where tha facilities for getting many kinds of small tools are better than in this country, perhaps a little advice as to the best way of getting such tools as may be required will not be out of place. In most of the large Hardware Stores, carpenters' tools will be found, put up in chests, at prices varying from five to fifty dollars or more ; but we should not advise the amateur to buy any of these, as tho quality of the tools is not always reliable, and as they are usually fitted up to make as much show as possible for the money, they contain many tools which are of very little use. The best way is to make a list of the tools required, and select them for your- self. The most important thing is to have the Cutting tools of good quality. We give below the names of some of the best makers of tools ; if you purchase any of these, you may be sure of the quality. On Saws, HENRY DISSTON, GROVES & SON. On Chisels and Gouges, BUCK BROS, MOULSON BROS. On Plane Irons, MOULSON BROS., WM. BUTCHER. On Files, P. S. STUBS, GREAVES the outside tool being applied to the inside, the respective notches and points will exactly fit into each other. If you were to examine the under side of these tools, shown at C, you wuald notice that the notches do not run straight, but slanting. They are in fact parts of screw threads \ and yon i 9 4 ?HE YOUNG MECHANIC. could make a tool of this kind out of a common screw nut, as I have shown you at D, only it would be too much hol- lowed out to make a good tool. Now, supposing you were to hold the tool A flat on the rest, while a cylindrical piece of wood revolved in contact with it, you would cut a series of rings only ; but if you were at the same time to slide the tool sideways upon the rest, so that by the time the wood had revolved once, the first point of the tool would have just reached the spot which was oc- cupied by the second when you started, you would have traced a screw thread of that particular pitch. This is what you have to learn to do always, and with certainty, no matter what pitch of tool you may be using, and it is easy to understand how difficult the operation must be to a beginner. Indeed, there are numbers of otherwise good turners who have never succeeded in mastering this work. Nevertheless it can be done, and, although difficult, it is not so much so as might be supposed. Indeed, at first sight it would hardly be believed possible, because each different pitch of tool, and each different-sized piece of work, requires a different speed of traverse to be given to the too}. But a practised hand will strike thread after thread without failure, and those whose trade is to make all sorts of screw-covered boxes and similar articles, will execute the work with as much speed and apparent ease, as they would any ordinary operation of turning. I shal] tell yon SCREWS AND TWISTS. 195 by and by, however, of several ways to escape this diffi- culty of screw-cutting, lathes being fitted in various ways to insure good work, in some cases by carrying forward the tool at exactly the right rate of traverse, and at others by moving along the work itself at the proper speed, while the cutting tool is held immovably, fixed in one position, and I will give one tool of great service which will guide you in starting the ordinary chasing-tool; and a good start is here truly " half the battle." The chasing-tool must run from right to left for an ordinary right-handed screw (and a left-handed one is very seldom required), so that the young mechanic need not trouble himself about it. Precise directions cannot be given further than to have a rest with a very smooth and even edge, which will not in the least hinder the traverse of the chasing-tool, and to get the lathe into sready, equable motion. Then hold the tool lightly, but firmly, keeping it at right angles with the work. Allow it only just to touch until you find you have got into the right swing. It is all a matter of knack and practice ; and if you succeed quickly, you may congratulate yourself. The inside chasing-tool is used in precisely the same way, running it from the outer edge of the hole inwards. To some this is an easier tool to use than the outside chaser. I cannot say that I find it so ; especially as one has to work more in the dark : unless the work is of large ig6 THE YOUNG MECHANIC. diameter like the cover of a box, and even then the work is sufficiently difficult owing to the shallowness of the lid, which necessitates the instant stopping of the tool for a fresh cut. For you must understand that you have to deepen the screw-threads very gradually, and it will take several traverses of the tool to cut them to a sufficient depth. The chasers require to be very sharp to cut wooden screws neatly, but observe you must only rub the upper flat face upon the oilstone, or, if a notch has been made by using the tools upon metal (they will cut brass well with care), grind them in the same way ; the great secret being to hold the tool quite flat on the stone. You will thus, even by continual grinding, only thin the blade of the chaser, which will thus last for a long time. A practised hand will even cut a good thread with any flat piece of steel filed into equal notches, but a screw-chaser is the only tool really fit for the purpose. The most effectual remedy for the screw-cutting diffi- culty, is unfortunately rather expensive in its best form. But in another, it is by no means costly ; and although it may not look so well as the first, it is equally effective, and extensively used by the turners at Tunbridge Wells, who make those beautiful little inlaid boxes and other articles. I shall explain this to you, therefore, first : A, is a lathe-head, something like the one I have already CHASING SCREWS. described, but you will notice that the mandrel is a much longer one, and has several short screws cut upon it, each one being of a different " thread" or "pitch."* This Kg. 52. mandrel runs through two collars, so that, besides turn- ing round, it can be pushed end-wise. Now, supposing * In the drawing, they are all accidentally drawn of the same pitch. 198 THE YOUNG MECHANIC. I was to hold the point of a tool firmly against either of the screws, and at the same time was to turn the pulley and mandrel, you will understand that it would run back- wards or forwards in its collars, at such a rate as the screw-thread compelled it to move. This is the plan of the traversing mandrel ; and now supposing that you had a box held as usual in a chuck, and while the mandrel wa? compelled to move end-wise as described, you were to hold a pointed tool against it, the tool would evidently cut a screw-thread of exactly the same pitch as that upon the mandrel against which the pointed tool first spoken of was applied. But in practice, a single-pointed tool held against the mandrel would not answer very well, and so the follow- ing plan is adopted instead, which answers perfectly. Fig. 52, C, is called a half- nut. It has a set of screw- threads, cut where the semicircular hollow is, which threads fit one of the screws on the mandrel. A whole row of these half-nuts are fitted to turn at one end upon a long bar, so that either one can be raised up at pleasure to touch the screw upon the mandrel, which has threads of the same pitch as itself, B. These, then, are ranged under the mandiel, and when it is desired to make it traverse in ita collars, one of these half-nuts is raised and kept up by & wedge placed underneath it. When no screw is required, a somewhat similar half-nut, but with merely a sharp edge instead of a thread, is raised, and this edge falls into a CHASING SCREWS. 199 notch or groove turned upon the mandrel, or sometimes a back centre-screw is added like D, and when no screw has to be cut, this is run up against the mandrel like aD ordinary lathe. In the more expensive traversing mandrels, although the principle is the same, there is a little difference in the ar- rangement of the different parts. The mandrel is not very much longer than usual ; and it has no screw-threads cut upon it. But a number of ferules like K, are made each with a screw upon its edge, and one of these of the desired pitch is slid upon the end of the mandrel at , fig. P, and is there held by a nut or otherwise, so that it cannot move out of its place. The half-nut is seen at a. It con- sists of a piece of brass or steel of the form shown with a hole in the middle, and a screw cut upon each hollow, so that it is a circle or set of half-nuts of different pitches. This slips over a pin at a, and when the screw b is turned, it draws up this pin and the nut attached, until the latter comes in contact with the ferule upon the end of the mandrel. This is very neat but expensive. Now, by far the cheapest and best way for the young mechanic, is to set boldly to work to conquer the difficulty of chasing screws by hand. There are even disadvantages in the expensive form of a traversing mandrel, which render it by no means a desirable mode of fitting up a lathe, and after all, the length of screw which it enables one to cut is very limited, THE YOUNG MECHANIC. and in addition, it is not every day, nor probably once a month, that screw-cutting will be necessary at all. My advice, therefore, is, do not get a traversing mandrel until you can cut screws well with the chaser. When you can do this, you will be able to judge of the advantage or dis- advantage of one. By far the greater number of common screws are cut without the lathe, by screw-plates, or stocks and dies, and the nut, or hole into which such screws are to fit, is cut with a tap. A screw-plate is a simple affair, a mere flat plate of steel, in which several holes are drilled, which are afterwards threaded by screwing into them taps, or hard cutting steel screws of the size re- quired; the plate is then hardened by being heated red- hot and suddenly cooled, after which being much harder than brass, iron, or steel which has not gone throu^ii such process, it will in turn cut a thread upon any of these by simply screwing them into it. But although this will answer for small and common screws, it is not at all suit- able for better ones, because the thread is burred up, not cut cleanly as it would be with a proper tool. A far better plan is- a stock and dies ; the latter being practically a hardened steel nut sawn in half, and fitted so that the two halves can be pressed nearer and nearer together as the screw thread becomes deeper. The dies are screwed up by means of a thumbscrew opposite to the handle. A SCREW-BOX. To use it, a piece of iron is filed up or turned to the required size, which must be exactly that of the finished screw. The dies are then loosened and slipped on to the ond of this screw-blank as it is; called, and are then slightly tightened upon it. All that is now required is to keep turning the tool round and round upon the pin, which it will soon cut into a screw thread. When the stock is at the bottom or top, you may tighten the dies, and so work up or down ; but never tighten them in any other part. If iron or steel is to be cut, use oil with the tool, but brass may be dry. If the screw is of steel, heat it red-hot and let it cool very gradually, to make it as soft as possible. The hole or nut, into which the screw is to fit, is to be drilled so as just to allow the taper tap to enter about a couple of threads ; a wrench, or, if small, a hand-vice is then applied to twist it forcibly into the hole, when the thread will be completed. -Take great care to hold the tap upright, or else, if it is a screw with a flat head which has. to fit into it, it will not lie correctly, but one side of the head will touch while the other is more or less raised. There are other modes of screw cutting, but at present J need only mention one, which is used for wooden screws alone. It is called a screw-box, and is only made to cut one size, a tap being always sold to match. You can, how- ever, purchase any size you like, from a quarter of an inch to 2 or 3 inches : "but the latter are only intended for very THE YOUNG MECHANIC. large screws, such as are used for carpenters' benches and various kinds of presses. A screw-box looks like a small block of wood with a hole in it, but if you take out two screws you will find a blade of a peculiar shape, which forms the thread by cutting the wood as it is screwed into the hole in the box. CHAPTER XI. HARD-WOOD TURNING. E now discard almost entirely the gouge and chisel used for soft woods, and fall back upon an entirely different set of tools, similar to those used for metal, bat ground to rather more acute angles. These tools are held horizontally upon the rest, because depressing the handles causes the bevel below the edge to rub upon the work ; and in addition, the grain of hard foreign woods ib such that it cannot well be cut by placing the tool at a more acute angle, as would theoreti- cally be required. Hence we can only regard these as scraping tools ; but as such they will do excellent work in skilful hands. I have said that we discard the gouge, but there are some woods that will bear this tool, to take off the roughest parts of the work, before the application of others. The roughing -tool, however, may now be considered to be the point-tool, and the round-end tool, or " round " as it 10 204 THE YOUNG MECHANIC. often called; a narrow one makes a good tool for this purpose. Hard wood is easier on the whole to work than soft, because we have for the purpose a large stock of tools ol all shapes, suitable to the various mouldings required. Hollows, round-beading tools, compound and simple moulding tools of various sizes, to say nothing of those which are made for use with ornamental apparatus, such as are required for fluting, beading, and eccentric work, spirals, and so forth. It is indeed in hard wood that most amateurs are accustomed to work ; ebony and ivory, singly or in combination, being more extensively used than any other. To turn a cylinder, or any work requiring to be held ai both ends, you will invariably find the cross-chuck the best to use, t 1 fork or prong not taking hold in the hard material, .tlough down to shape as before, using the gouge if it will work, but keeping the rest as close as possible, and only taking a light cut. Then finish roughing with a round-tool, and proceed generally as in soft wood turning, except inasmuch as you have to scrape instead of cutting the work into form. In addition to the tools already described, you will have to obtain a few beading-tools, if you want to do very good work, for these give far more beautiful mouldings than you can cut in any other manner. Fig. 53, A to C, represent SIDE-PARTING TOOL. 205 these. The bevel is on the under side, and it is better to interfere with it as little as possible, by always sharpening the flat face only. If it should be necessary r , however, to touch the bevil, it must be rubbed by a slip of oilstone, rounded on the edge, as used for sharpening gouges. Conical grinders, revolving in the lathe, are also used, especially for small beading-tools, to be fixed in the slide- rest. In the same figure, D and E represent another useful hard-wood and ivory tool. It is called the side-parting tool; and it is usual to have several of these, the hooka increasing in length. The edge is only on the extreme end of the hook. These tools are used for economy's sake to cut solid blocks of ivory and hard-wood from the inside of boxes, instead of cutting the material into a heap of useless shavings. Similar tools, G, H, curved instead of rectan- gular, serve to cut out a solid piece from the inside of P bowl. In ivory work it is essential to use these tools, because such material is very costly ; $2.50 a lb., and up- wards, being a common price. K is given to show what are meant by beadings. If these are exactly semicircular in section, they are far more beautiful in appearance than if of such curves as can be roughly cut by a chisel. The bead-tools are beautifully formed for this very purpose. To use the same side-parting tool, you must proceed as follows, which you will under- stand by the fig. L : A common straight part ing -tool or 306 THE YOUNG MECHANIC. THE RING-TOOL. 207 narrow chisel is first applied to the face of the work to cur a deep circular groove or channel, as shown by the white space at N, and in section at L. This allows the narrowest of the hooked tools to be applied to under-cut the solid core x. This being withdrawn, a rather longer hook is applied, the hook being held downwards as at 0, until it reaches the spot where it is to work, when it is gradually turned up (bevel below). Eventually, it is plain that the solid core or centre block x will fall out entire, which may be used for other purposes. M shows how a similar but curved block can be removed from the inside of a cup or bowl, the curved tool not requiring an entry to be made for it, as it cuts its own way entirely from first to last. P and Q show a ring-tool and the method of using it. A recess is turned in the face of a piece of wood as it it was intended to hollow out a box. The ring-tool is then applied bevel downwards, and with the left cutting edge a bead is cut half-through from the inside. The right edge is then applied to the outside, and when the cuts meet the ring neatly finished, will fall off. "With this tool you can turn them very rapidly, and they will require only a rub of sand-paper to finish them. R, S, T are three more tools for hard wood. The first two cut on the outside of the curved part all round. These would be used to hollow out humming-tops and all similar 208 THE YOUNG MECHANIC. articles, and to finish the insides of bowls, for which T ia also designed. Indeed, I might go on to describe all pos- sible shapes of curved tools, each intended for some special work; but you will not do better than to go to Fenn, Buck, or any tool-maker in London, or elsewhere, and pick out at 7s., or so, per dozen, all shapes and sizes, or if you live at a distance and write to either of the above, they will select you the most useful; and you can trust these tradesmen and all first-class ones to send you no tools which are not of the best quality. In finishing best work in hard wood, be very careful of all sharp edges of mouldings. Sand and glass paper round off these, and spoil the beauty of the work. If you are obliged to use such substances, touch off again the edges with very keen tools, which ought to leave brighter and more beautiful surfaces than any sand-paper can produce. Indeed, the secret of finished work in hard wood is to have tools whose edges and bevels are polished. In ornamental eccentric and rose-engine turning, where to use sand-paper would be to ruin the appearance of it, the little drills and cutters pass through three stages of sharpening, being ground on the oilstone, finished on a slab of brass, fed with oil and oilstone powder, and polished on a slab of iron with oil alone or oil and rouge. After this every cut that 'is made with them reflects the light; and as the surface is otherwise purposelv erailed or dulled by cutting a series of .fine lijjht TURNING IN METALS. 209 rings with a point tool, the pattern itself shows out clearly and lustrously. TURNING BRASS AND OTHER METALS. I shall now teach you how to turn iron and brass, which, though harder than wood, are not very difficult to cut, if you go to work in a proper manner and understand how tc use your tools. What these are like I have already told you, and also how to mount a bar in the lathe by using the driver or point-chuck with a carrier. If the piece to be turned is not a bar, you will have to drive it into a chuck of wood, or clamp it upon a face-plate, or in a self-centring chuck if you have one. I shall suppose, first of all, a mere straight bar of iron, centred at the ends, as I have shown you. Take off the lathe- cord that you use for wood, and fit one to go upon the largest part of the mandrel pulley, 'and the smallest upon the fly- wheel. When you now put your foot upon the treadle to work at your usual speed, you will find the mandrel turn quite slowly ; but I may at once tell you, that what you lose in speed you gain in power. Set your rest for iron (which is not that used for wood, but one with a broad, flat top) so that it stands a little below the central line of the lathe mandrel and work, which will bring the edge of the tool exactly upon that line. This is always the position of the tool for metal-turning, at any rate for iron. 1HE YOUNG MECHANIC. Begin by trimming the end of the bar next to the back centre. Use a graver, held as I directed you; that is, with the bevel flat upon the face of the iron, which is in this case the end of it. Only let the point cut, and a very little of the edge beyond it, and do not expect to take a deep cut so as to bring off a thick shaving. In metal work you will always have to proceed slowly, but nothing is more pleasant when once you can do it well. You will at first have to experimentalise a little as to the exact angle at which to hold the tool, but you will soon find out this ; and the advantage of hand- tools is, that you can always feel as well as see how they are working, and can ease them here and there to suit the material. It is rather difficult at first to hold the tool still in metal-working, but, like all else, it becomes easy by practice ; so much so, that to hold the tool steadily in one hand is not only possible, but is the mode always followed by watchmakers. While you are about it, you should turn the graver over and try it in other positions ; for although the two sides of the bevel nearest to the point are the only ones to be used, these may be applied in either direction, because they are both sharpened to angles of 60, and so long as you present them at the correct angle (the smallest possible in respect of the work), it matters not which face of the tool lies uppermost. After squaring otf one end, the approved plan is to remove the carrier, reverse the bar, and do the same to the other eud. Then begin to TURNING IN METALS. turn from the right hand. Place the graver as before, with the point overlapping the end very slightly (so as only to use the extremity of the cutting edge close to the point), and take off a light shaving along the bar for a distance of about half an inch, or even a quarter, keeping the edge of the graver which is on the rest in one position, and moving the tool, not by sliding it along the rest, but by using the point upon which it lies as a pivot. It is very difficult to describe this exactly, but Fig. 52, 0, will help to explain it. The tool is to rest upon one spot, and the point to move in short curves like the dotted lines, being shifted to a new position as you feel it get out of cut. The left hand should grasp the blade and hold it tightly down upon the rest, while the right moves the handle to and fro as required. The curved dotted lines are necessarily ex- aggerated, but the principle of the work is this, whether you use a graver or a heel-tool. You should turn about half an inch quite round, and then go on to the next, by which you will always have a little shoulder upon the work for the tool to start upon, and this will be nice, clean, bright metal, and will not blunt the tool. But if you go to work differently, so that the edge of the tool comes continually in contact with the rough outside of the iron caused by the heat of the fire, and which is exceedingly hard, the point of the tool will be quickly ground down, while the iron will not be cut into at alL THE YOUNG MECHANIC. I need tell you no more about turning a bar of iron in the lathe, because the above directions apply in all cases ; but if you have to turn the face of a piece of metal that is carried in a chuck of some kind, you should always work from the middle towards the edge, and if the graver is used, its bevelled face will lie towards you during the pro- cess. Take care to chuck the metal very firmly, for it is most annoying to have it suddenly leave the chuck or shift its position after you have been at the trouble of turning part of it truly. In such case it is very difficult to replace it exactly as it was before, and all your work has in con- sequence to be gone over again. When taking the final cut, or before, if you like, dip the end of the tool into water, or soap and water, and see the effect. The surface turned in this way will be highly polished at once, and the tool will cut with much greater ease, so that a large, clean shaving will come off. When using a slide-rest, you will find it always better to keep water just dripping upon the work and point of the tool ; but there is a drawback, never- theless, to this plan, for, as might be expected, it makes a mess and rusts the lathe, and sometimes the work as well, so the water must be constantly wiped off it. THE SLIDE -REST. I shall now pass on to describe a mechanical arrangement called a slide-rest, of which there are two separate and dis- THE SL1 r DE-REST, 213 tinct forms, one for metal and one for ornamental turning in ivory and hard wood. The ornamental work that can be done 1 shall pass by for the present, because few boys are provided with the costly apparatus required, and I am rather addressing those young mechanics whose tastes in- cline them to model machinery and to practise the various operations of mechanical engineering on a small scale. To such a slide-rest is an almost necessary addition to the lathe, for there is a great deal of work which, I may say, cannot be done without it ; for instance, boring the cylinders of engines (except small ones of brass), turning the piston- rods and various pieces which require to be accurately cylindrical and of equal size, perhaps for the length of a foot or more. Hand-work has accomplished something in this way in olden days, but the inability of workmen to advance beyond a certain standard of perfection with hand- tools alone, became such a hindrance to the manufacture of the steam-engine, as improved by Watt and others, that had not Maudsley, Nay smith, and others developed the principle of the slide-rest and planing machine, we should not yet have lived to see those gigantic engines which tear along like demon horses with breath of fire, at the rate of sixty miles or more in as many minutes. So likewise would various other machines, which now appear absolutely necessary to supply our various wants, have stood in their primitive and imperfectly developed forms; for it is necessary, 214 THE YOUNG MECHANIC. before constructing a machine, to have the means of turning cylindrical parts truly, and producing perfectly level plates where required. The object of a slide-rest is to provide means for holding a tool firmly, and giving it a power to traverse to and fro and from side to side, so that by the first we may be able to cause such tool to approach or recede from the work, and by the second we may cause it to move in a perfectly straight line along its surface from end to end. This is accomplished in the following manner : The drawing being a representation of one of the first machines con- structed for the purpose. A rectangular frame, A, of iron is carried by a pair of strong uprights, B B, fixed to the sole-plate, C, by which it is attached by a bolt to the bed of the lathe. Lengthwise of this frame runs a screw, pre- vented by collars from moving endwise, but which can be turned round by the winch-handle, D. Thus a nut through which this screw passes, and which only has endwise motion, will, when the latter is turned by its handle, traverse it from end to end in either direction, ac cording as the screw may be turned from right to left or the contrary. This nut is attached to the under part of a sliding-plate, E, which has a part projecting between the sides of the frame, and also two others on its outside, by which it grasps the same with great accuracy, and is prevented from any shake or play as the whole THE SLIDE-REST. 215 with the nut is made to traverse to and fro along the frame. Lengthwise of this sliding-plate, that is, in a direction the opposite to that of its own traverse, are two bars bevelled underneath, fixed exactly parallel to each other, which are so arranged to guide the cross traverse of another plate with chamfered edges to fit the bevels of the guide bars. This second plate has on its upper surface two clamps which secure the tool. It is plain, then, that by this ar- rangement the two required movements are attained, the lower plate sliding along in one direction parallel with the lathe-bed, and the other across it. In the original rests, this upper plate with the tool was moved by hand, and in the modern rest for ornamental turning (which this was also constructed for) the same is done, but a hand-lever is added for the purpose. But although a similar arrangement is needed for metal, it is plain that the top plate should have a more easily regulated motion, and that we should be able to advance the tool as near the work as may be desired, and then to retain it securely at that distance while giving the necessary move ment in the direction of the length of the object to be turned. The method of effecting this is at once suggested by the ecrew and nut of the lower part, and by merely adding to the top a similar arrangement, the desired end is at once attained. 216 2 HE YOUNG MECHANIC. The actual construction of such rest varies somewhat, but Fig. 54, H, shows it in its most ordinary form. The lower part is, of course, to be clamped down securely to the Tig. Si. lathe-bed, there being a projection below which is made to fit accurately between the bearers similar to that beneath the poppits. This projection secures the correct position of the rest, of which one frame or plate will travel length THE SLIDE-REST. 217 wise of the bed, while the other will move exactly at right angles to it. But in the compound slide-rest, which is very general, there is also a third circular motion, by which the upper part can be set at any angle with the lower, instead of being permanently fixed at right angles to it. By this the tool can be made to approach the work more and more as it passes along it ; and it will therefore cut deeper at one end of its traverse than at the other. The result will be that what is thus turned will not be a true cylinder, but a cone, i.e., it will be larger at one end than the other, although otherwise smooth and even. We are thus provided with the most valuable addition to the lathe ever devised by mechanics, and it is no longer a question of the strength and skill of the workman whether we can produce a perfect piece of work, but simply of the accuracy with which the lathe and rest are constructed, and of the form and condition of the tools to be used. The latter are not exactly like those ordinarily used, although the principle of the cutting angles already laid down needs to be adhered to even with more unfailing attention than that required for the correct formation of hand-tools. Moreover, it is plain that here we shall no longer feel whether the tool xs working as it ought to do we shall be unconscious }f the precise amount of strain that is being brought to bear against its edge, and if it is by chance working in a bad position, at a wrong angle, we cannot re- adjust it in a THE YOUNG MECHANIC. moment as we could a hand-tool by a slight movement of the fingers or wrist. Hence you will see at once how very important it is that tools for the slide-rest should be shaped with the most rigid adherence to correct principles ; and, further, that they should be so fixed in the slide-rest as to meet the work at the precise angle, and at the height exactly suited to the material of which it is composed. As regards the latter point, it may be taken as an almost invariable rule that the work should be attacked on its axial line (that is, a line that would run from end to end of it dividing it lengthwise into equal parts, or, as it would commonly be named, its middle line). If the tool meets it above this, it is most likely that it will rub against it, and the point will be out of cut. If it meets it below, there will be a tendency for the point to catch in, and the work to roll up upon the face of the tool, which, in fact, it very often does with careless workmen, and then there comes a smash of some kind lathe centres snapped off, the tool broken, the bar bent beyond remedy, and possibly the operator's toes made un- pleasantly tender. The most common slide-rest tool for outside work is that given at H a . It is made straight, as shown, or bent sideways to right or left to cut shoulders on the work, or enter hollows, or creep sneakingly round corners, or any other of those crooked ways in which man delights ; but THE SLIDE-REST. 2i. I have in a previous chapter told you that the atmospheric pressure equals 15 Ibs. on each square inch, so that if ths surface of the valve which is exposed to the air is 1 inch in area or surface, it is pressed down with a force of 15 Ibs. The steam, therefore, inside the boiler will not raise it until its elasticity exceeds this atmospheric pressure. If, there- fore, we desire to have only just 15 Ibs. per square inch pressing against the inside of the boiler (i.e., a pressure of " one atmosphere," as it is called), we have only to load the valve so that, inclusive of its own weight, it shall equal 15 Ibs. But it is plain that we must not load it at all in reality ; for a flat plate, 1 inch square, of no weight, STEAM PRESS URE. 3 1 1 is all that is needed, the atmosphere itself being the load. Suppose, then, that we do load it with 15 Ibs. in addition to the 15 Ibs. with which nature has loaded it, we shall not find the steam escape until it presses with a force of 30 Ibs. on the square inch, or two atmospheres (which, however, is not 30 Ibs. of useful pressure upon one side of the piston, if the cylinder is open as in an atmospheric engine, but only 15 Ibs.) This is not the strain which the boiler has to stand, because the atmosphere is pressing upon it and counteracting it up to the 15 Ibs., so that this strain tend- ing to burst it is but 15 Ibs. The number of pounds, there- fore, which is straining the boiler can readily be seen ; being always that with which the safety-valve is loaded, and this is also the useful pressure for doing any required work. Un- fortunately, however, even in the best constructed engines, a pressure of 15 Ibs. upon the boiler by no means represents that in the cylinder. Now it would be inconvenient to place weights upon the safety-valve itself, and therefore a lever is added, as seen in the sketch, with a weight hung at one end of it. This is shown at B, Fig. 68, where a section of the valve is given with its stem passing through a guide to insure the correct motion of the valve. The lever is hinged at one end : and the rule of the pressure or weight which is brought to bear upon the valve is, that it is multiplied by the distance at which the weight hangs from the valve, compared with its distance from the hinge 3 ia THE YOUNG MECHANIC. or fulcrum. If a weight of 7 Ibs. is hung at 1, i.e., at a distance as far on that side of the valve as the fulcrum ia on the other side of it, 7 Ibs. will be the actual power exerted ; at 2, where it is twice the distance, it will be doubled, and, as shown in the drawing, a pressure of 14 Ibs. will be brought to bear upon the valve; while, if the weight is hung at 3, it will exercise a force of 21 Ibs. This is very easy to understand and to remember. Sometimes (always in locomotives) the weight is removed and a spring balance is atl ached at the long end. Upon this is marked the actual pressure exerted; there being a nut to screw down, and thus bring any desired strain upon the spring. Mind, however, in case you should try this in any of your models, that the scale marked on the balance when you buy it must be multiplied, as before, according to the length of your lever. Thus, u 1 Attach such a balnnce at 3 of the draw- ing, a real weight of 5 u~ shown by the balance will be 3 x 5, or 15 Ibs. upon the valve, and a balance made far such engine would be marked 15 Ibs., to prevent the possi- bility of dangerous error. ENGINES WITHOUT SLIDE-VALVES EASY TO MAKE. Having been led on from the atmospheric engine to that of Watt's, and to slide-valve engines generally, I am now going backward a little to a class easier to make, because they have no slide-valves, nor oven four-way cocks ; and OVERCOMING DIFFICULTIES. 313 then I shall have done with engines. But I dare say some of my readers will wonder why I have said so little about condensers and condensing engines. I am sure they will wonder at it if they understood what I explained of the advantage of a vacuum under the piston ; so that 1 5 Ibs. pressure upon the piston means 15 Ibs. of useful work, in- stead of 30 Ibs. being required for that purpose. But con- densing engines are utterly beyond a boy's power. They require not only a vessel into which the steam is injected at each stroke, but there must be a pump to raise and inject cold water to condense the steam, and a pump to extract from the vessel again this water, after it has been used, and a cistern, and cold and hot wells ; and all this is difficult to make so as to act; and I am sure no boy cares for a steam engine that will not work. Moreover, I have given you difficult work as it is work that many of my readers will no doubt be afraid to try yet I did it on purpose ; because if small boys are unequal to some of it, their big brothers are not, or ought not to be ; and mechanical boys must look at difficulties as a trained hunter looks at a hedge viz., with a strong desire to go over it, or through it, or any how and some how to get to the other side of it. Indeed, you must ride your mechanical hobby very boldly and with great pluck, or you won't half enjoy the ride. However, I am quite aware that I have led you into several difficulties, and therefore now I propose to set before yo?j 3 14 THE YOUNG MECHANIC. some easy work as a kind of holiday task which will send you with fresh vigour to what is not so easy. The engines without slide-valves have also no eccentrics and no connecting-rods. There is just a boiler, a cylinder piston, piston-rod, and crank, and you have the sum total, save and except the fly-wheel. These are direct-action engines, the cylinders of which oscillate like a pendulum, and the piston-rod itself is connected to the crank, doing away with the necessity for guides. Fig. 69, A, shows one of these engines, and you see that the cylinder leans to the left when the crank is turned to that side ; and if you turn the wheel to the right, the crank will presently cause it to lean the other way ; and thus, as it turns on a pin, or "trunnion," as it is called, it keeps on swinging from side to side as the wheel goes round. Now, when it is in its first position, the piston is at the bottom of the cylinder, and it then needs to have the stean. admitted below it to drive up the piston ; but when this has passed its highest position, and the cylinder is turned a little to the right, the piston must be allowed to descend, and, therefore, we must let out the steam below it. We ought, at the same time, to admit steam above the piston to force it down ; but, in the simplest models, which are sailed single-action engines, this is not done. The fly- wheel, having been set in motion, keeps on revolving, and, by its impetus, sends down the piston quite powerfully OSCILLATING CYLINDERS. enough to overcome the slight resistance which is offered by the friction of the parts. Now, you can, I daresay, easily understand that it is pos- sible to make this to-and-fro motjon of the oscillating cylin- der open first a steam-port to allow steam to raise the piston, and then an exhaust-port to let it blow off into the air. Thia is exactly what is done in prac- tice, and it is managed in the following manner : B, of Fig. 69, shows the bottom of the cylinder, which is a solid piece of brass filed quite flat on one side, and turned out to receive the end of the brass tube, which, gener- ally speaking, is screwed into it to form the cylinder, this being the easiest way to make it. In the middle of the upper part of the flat side you see a white steam-port, and below it a round white spot, which is the position of the pin, or 3 i6 THE YOUNG MECHANIC, trunnion, on which it oscillates. Fig. 69, C, is a simila! piece of brass, which is fixed to the top of the boiler. Iii this, on the left of the upper part, is also a port, which is connected with the boiler by a hole drilled below it to admit steam. On the right is also a port, which is merely cut like a notch, or it may go a little way into the V)ss, and then be met by a hole drilled to meet it, so as to form the escape or exhaust port. Between and below these is the hole for the trunnion. Now, you can, I think, see that if the cylinder stands upright against this block, as it does when the crank is vertical (or upright) and on its dead points, the port at the bottom of the cylinder would fall between the two on this block of brass, and, as they are both flat and fit closely, no steam from the boiler can enter the cylinder. Nor do we want it to do so, because, if the crank is on a dead point, no amount of steam can make the piston rise so as to move it. But now, if we move the cylinder to the left, which we can do by turning the wheel, we shall presently get the crank at right angles to its former position, and, also, we shall bring the steam-ports in the cylinder and block together, so that steam will enter below the piston. But, practically to get as long a stroke as possible, steam is not allowed to enter fully until the crank is further on than in a horizontal position, that is, approaching its lower dead point ; and this is the position in which to put it to start DOUBLE-ACTING ENGINES. 317 the engine. By altering the shape or the position of the port a little, we can so arrange matters as to let steam enter at any required moment. Steam having entered, the piston will rise rapidly, forcing up the piston, and presently, by the consequent revolution of the fly-wheel, the cylinder will be found leaning to the left, and at this moment the piston must evidently begin to descend. At this very time the steam-ports will have ceased to correspond, but the port in the cylinder will come opposite the exhaust-port in the brass block, and this port is made of such size and shape that the two shall continue to be together all the time the piston is descending ; but, the moment it has reached the end of its downward stroke, they cease to correspond in position, and the steam-port begins again to admit a fesh supply of steam. The pillar attached to the brass boss has nothing to do with it, but is one of the supports of the axle of the fly- wheel, as you will understand by inspection of A of this same drawing. Such is the single-action model engine, of 'no power ', but a very interesting toy and real steam engine. The double-action engine is very superior to the foregoing, which, I may remark, has no stuffing-box, and of which the piston is never packed. I may also add, that the crank is formed generally by merely bending the wire that forms the axle of the wheel, and putting the bent end through the hole 3i8 THE YOUNG MECHANIC. of a little boss or knob of brass, screwed to the end of the piston-rod. Here you have no boring of cylinders to accomplish, but the cylinder cover, piston, and whee, (often of lead or tin) require the lathe to make them neatlj . Many an engine, however, has been made without a lathe, and I have seen one with a bit of gun-barrel for a cylinder, and a four-way cock of very rough construction, that was used to turn a coffee-mill, and did its work very well too. But I must go at once to the double-action oscillating cylinder, in which, although a similar mode of admitting steam is used, it is arranged to admit it alternately above and below the piston, the exhaust also acting in a similar manner. After the explanation I have given yon, however, of the single-action engine, you will, some of you, I think, jump at a conclusion almost directly, and perhaps be able to plan for yourselves a very easy arrangement to accomplish the desired end. All boys, however, are not " wax to receive, and adamant to retain " an impression ; for I have known some who need an idea to be driven into their brains with a good deal of hard hammering. Stupid ? No. Dull ? No, only slow in getting hold, and none the worse for that gener- ally, if the master will but have a little patience ; for when they do get hold, they are very like bulldogs, they won't let go in a hurry, but store up in most retentive minda what they learned with such deliberation. CIRCULAR PORTS. 319 THE DOUBLE-ACTION OSCILLATING ENGINE. The cylinder of the double-action engine is of necessity made with ports very similar to those of the horizontal engine already described. There is a solid piece attached to the cylinder as before, which is drilled down to the upper and lower part respectively of a central boss, turned very flat upon the face, and which has to work against a similar flat surface as in the last engine. But the ports in the latter are four instead of two, and in an engine with upright cylinder would be cut as follows, and as shown in Fig. TO, C. Those on the right marked st are steam -ports, which, being drilled into one behind, are connected with the boiler. The other two marked ex, are similarly exhaust-ports opening into the air. The spaces between a b and c d of fig. C must be wide enough to close the steam-ports in the cylinder, when the latter is perpendicular and the engine at rest. When the cylinder leans to the left, oscillating on the central pin between the ports in the middle of the circle, the lower port of it will evidently be in connection with the steam-port in C, while the upper port of the cylinder will be opposite to the exhaust. As the cylinder is carried over towards the right, the upper steam-ports will come into action in a similar way, while the lower exhaust-port is also carrying off in turn the waste steam. The impetus, therefore, of the .520 THE YOUNG MECHANIC. fly-wheel has here only to carry the ports over the * a b, c d, and to prevent the crank stopping on the two dead points. This, therefore, is a genuine double-action engine, and will answer, even on a large scale, very satisfactorily. If you do not quite understand the action of these ports, cut out two pieces of card, E F. Let E represent the cylinder. Draw circles, and cut two ports. Cut another piece of card DETAILS. 321 to represent the brass block, with ports, c d; pin them together through the centres of the circles, and they will easily turn on the pin, Mark the ports, so that you will see at a glance which are steam and which exhaust. Now cut out the ports with a penknife, and as you work the two cards together, swaying that which represents the cylinder to and fro upon the other, you will see when the ports in each card agree with one another, and which are opposite to which. This will teach you far better than any further written explanation. You will also see that, instead of making the steam and exhaust ports respectively with a division between, the two steam-ports may be in one curve united, and likewise the two exhausts ; but take care not to unite the exhaust with the steam-ports. There is no way so easy as this of reversing the action of the steam; it is, in fact, a circular slide-valve, but wonderfully easy to make, because you have no steam-case to make, nor any attach- ments whatever. The faces of the valve are kept in close contact in one of two ways either the centre-pin is fixed into the cylinder face, and after passing through the brass boss with the ports, is screwed up with a nut at the back ; or else there is fixed a small pillar or upright on the opposite side of the cylinder, and a little pointed screw passing through this presses against the cylinder, and makes a point of resist- ance, against which it centres, and on which it turns. This x THE YOUNG MECHANIC. is shown at fig. A. A small indentation is made where the point comes in contact with the cylinder. In a locomotive engine there are two such cylinders, working against opposite faces of the same brass block containing the ports. The cranks are also two, on the shaft of the driving-wheels, and are at right angles to each other ; so that when one piston is at the middle of its stroke, the other is nearly or quite at the end of it. Thus, between the two there is always some force being exerted by the steam; and the dead points of one crank agree with the greatest leverage of the other. In locomotives, too, the cylinders generally are made as in the present drawing, viz., to oscillate on a point at the middle of their length ; but it is just as easy to have the two ports meet at the bottom instead, so that the point of oscillation may be low down, like the single-acting cylinders of the last sketch, and this is generally done when the cylinder is to stand upright. There is no occasion for me to draw an engine with double-acting oscillating cylinders, because in appearance it would be like the single-acting one ; but whereas the latter is of absolutely no use, seeing that the greater part of its motion depends on the impetus of the fly-wheel, the former can be made to do real work, and is the form to be used for marine and locomotive engines. For the former, oscillating cylinders with slide-valves are used in practice ; TRUE LABOUR. 323 but for real locomotives fixed cylinders are always used. Of course either will answer in models, and it will be good practice to try both. I have now given sufficient explanation of how engine* work, and how they may be made, to enable my young mechanic to try his hand at such work. The double-action oscillating engines especially are well worthy of his atten- tion, as he may with these fit up working models of steam- boats and railway trains, which are far more difficult to construct with fixed cylinders and slide-valves. I shall therefore close this part of my work with a description of one or two useful appliances to help him in the manipula- tive portion of his labour, for here, as in most other matters, head and hand and heart must work together. The heart desires, the head plans, tae hands execute. I think, indeed, I might without irreverence bring forward a quotation, written a very L-ng time ago by a very clever and scientific man, in a very Holy Book : "Whatsoever thy hand findeth to do, do it with all thy might." Depend upon it success in lif 3 depends mainly upon carrying into practice this excellent advice. If you take up one piece ol work, and carelessly and listlessly play at doing it, and then lay it down to begin with equal indifference something else, you will never become either a good mechanic or a useful raan. If you read of those who have been great men lights in their generation yon will find generally that 3 a 4 THE YOUNG MECHANIC. they became such simply by their observance of that ancient precept of the wise man. They were not so marvellously clever they seldom had any unusual worldly advantages ; but they worked " with all their might," and success crowned their efforts, as it will crown yours if you do the mm*. CHAPTER XV. HARDENING AND TEMPERING TOOLS. PROMISED in a previous page to describe a little stove for beating soldering-irons, and doing other light work. It is made as follows, and will be found very useful. Fig. 71, A, is a tube of sheet-iron, which forms the body of the little stove. Four light iron rods stand out from it, which form handles, but these are forked at the ends, and thus become rests for the handles of soldering-irons, or any light bars that are to be heated at the ends. Below is a tray, also of sheet-iron, upon short legs to keep it off the table for this is a little table-stove. C is the cast-iron grate. You can buy this for a few pence first of all, and then you fit your sheet-metal to it. It will rest on three or four little studs or projections riveted to the stove in- side ; or you can cut three or four little places like D, not cutting them at the bottom line, a b, but only on three suit's, aiid then bend in the little piece so as to make n 3 z6 2 'HE YOUNG MECHANIC. shelf. If the stove is about 4 inches high above the grate, and 2 or 3 inches below it, and 6 inches diameter, it will be sufficiently large for many small operations ; but that the fuel may keep falling downwards as it burns, the lower part should be larger then the upper, and, to admit plenty of air should be cut into legs as shown. Round the top are cut semicircular hollows, in which the irons rest. To increase the heat, a chimney or blower, B, is fitted, which has also openings cut out to match those of the lower part, so that the soldering-irons can be inserted when this chimney is put on. If, however, this is not required, but only a strong draught, by turning the chimney a little, all the openings will be closed. A still longer chimney can be added at pleasure. A hole should be made at the level of the grate to admit the nozzle of an ordinary pair of bel- lows. This stove you would find of great service, and it may be fed with coke and charcoal in small lumps. Now you may make the above far more useful. It will make a regular little furnace, and not burn through, if you can line it with fireclay. In London and large towns you can obtain this ; and it only needs to be mixed up with water, like mortar, when you can plaster your stove inside an inch thick or more, making it so much larger on purpose. There is no need to do this below the level of the grate ; but if you cannot get fireclay, you may do almost as well by getting a blacklead-meltingpot from any ironfoundry, DETAILS OF CONSTRUCTION 3 2 7 and boring a few holes round the bottom for air, and fitting it inside your little iron stove. In this you can obtain heat enough to melt brass, and it will last a great deal Fig. 71. longer than the iron alone, which will burn through if you blow the fire much ; but for general soldering, tempering email tools, and so forth, you need not blow the fire, as the hood and chimney will sufficiently increase the heat. There is no danger in the use of this little fireplace, but of course you would not stand it near a heap of shavings, unless you are yourself a very careless young " shaver." HOW TO TEMPER TOOLS. There is no reason why the young mechanic should not 328 2 HE YOUNG MECHANIC. be told how to make his own tools, and how to harden and temper them, because he ought to be a sort of jack-of-all- trades ; and perhaps he may break a drill or other sniajl tool just in the middle of some special bit of work, or hi drill may be just a little too small or too large, aud there he will be stuck fast as a pig in a gate, and unable w -set himself right again any more than the noisy squeaker aforesaid. But to a workman a broken drill means just five minutes' delay, and all goes on again as merrily as before ; and as we wish to make our young readers work men and not bunglers, we will teach them this useful art at once. Drills, are made of steel wire or rods of various sizes. In old times they were made square at one end, to fit lathe- chucks or braces, but now, for lathe-work, they are gener- ally made of round steel, and fastened into the chuck with a set screw on one side. In this way they can be more easily made to run true. But there are so many kinds of drills that I suppose I had better go into the matter a little only I have not room to say much more. Look at Fig. 72, and you will see some of the more usual forms of drills used, but these are by no means all. You will not indeed require such a collection ; and yet, if you should grow from a young mechanic into an old one, I dare- say you will find yourself in possession of several of them. The first, labelled 1, is the little watchmaker's drill, of DIFFERENT DRILLS. which, nevertheless, this would be considered a very large size. It is merely a bit of steel wire, with a brass pulley upon it, formed into a point at the largest end, and into a Pig. 78. - drill at the other. The way it is worked is this : At the side of the table-vice that is, at the end of its jaws or chops or chaps are drilled a few little shallow holes, in which the watchmaker places the point at the thickest end; the drill-point rests against the work, which he holds in his left hand. A bow of whalebone, a, has a string of fine gut such as is used for fishing, or, if the drill is very email, a horse-hair ; and this is given one turn round the 330 THE YOUNG MECHANIC. brass pulley before the drill is placed in position. The bow is then moved to and fro, causing the drill to revolve first in one direction and then in the other. The general work is in thin brass, and therefore these little tools are sufficiently strong for the purpose. Some of the drills and broaches (four or five, or even six sided wires of steel) are so fine that they will bend about like a hair, and yet are so beautifully made and tempered as to cut steel. No. 2 is a larger drill, even now much used. In prin- ciple it is exactly similar to the last, but the pulley it> replaced by a bobbin or reel of wood, made to revolve by a steel bow with a gut string, or a strong wooden bow. The drills, too, are separate, and fit into a socket at the bottom of the drill-stock. The large end is pointed, as in the last, and is made to rest in one of the holes in a steel breast- plate, 6, which is tied to the chest of the operator, who, by leaning against it. keeps the drill to its work, while both hands are free to hold the latter steady. There is a modi- fication of this tool, invented by a Mr Freeman, intended to do away with the bow. The bobbin or reel is turned without raised ends, and is worked by a flat strip of wood covered with india-rubber, and turned at one end to form a convenient handle. The having to twist the bow- string round the drill, which is always a bother, is thus done away with. No. 4 is a drill-stock similar to the last, but in place of ARCHIMEDEAN DRILLS. 331 the breast-plate a revolving head or handle is put to the top, in which the point works. This is held in one hand, while the drill-bow is worked by the other. This is also generally held against the chest, as the hand alone does not give sufficient pressure. Heavy work, however, can- not well be done by these breast-drills, and they are liable to cause spitting of blood from the constant pressure in the region of the heart and lungs. No. 3 is the Archimedean drill-stock, now very common , but originally invented by a workman of Messrs Holt- zapfiel's, the eminent lathemakers of London. It now comes to us as an American drill-stock. It is a long screw of two or more threads, with a ferule or nut working upon it. The upper end revolves within the head, which is of wood ; the lower end is formed into a socket to receive the drills, which revolve by sliding the ferule up and down. Some are 14 inches long, and others not more than 5. The first are used with the pressure of the chest, the latter with that of the left hand. For light work these are very useful, and you will seldom need any other in the models of small engines, &c. No. 5 is another watchmaker's drill, but serves also as a pin- vice to hold small pieces of wire while being turned or filed in the little lathes which are used in that trade, and which are worked by a bow with one hand, while the tool is held in the other. This is by no means a useless tool, 332 THE YOUNG MECHANIC. even without the pulley. It is made by taking a round (or better, an octagon, or five or six sided) piece of steel, drilling the end a little distance, and then sawing the whole up the middle. The slit thus made is then filed away to widen it, and leave two jaws at the end, which grasp the pin or drill; a ring slips over, and keeps the jaws together. We now come to fig. 6, which represents the best of all drills for metal. It is really American this time, and does our Transatlantic cousins great credit, as does the machinery generally invented or made by them (the Wheeler and Wilson sewing-machines for instance). The steel of which this drill is made is accurately turned in a lathe, and the spiral groove is cut by machinery. This groove acts in two ways first, as allowing the shavings (not powdery chips) to escape as the tool penetrates, but as forming the cutting edges where they (for there are two) meet at the point. These, however, require a lathe with a self-centring chuck made on purpose. They are sold in sets upon a stand, chuck and all complete, and each is one-thirty-second of an inch larger than the other. Some are as small as a darning-needle, or less, and they run up to an inch or so in diameter. There are large and small sets. We now pass to the old-fashioned smith's brace, fig. 7, shown in position, drilling the piece e. Pressure is kept up either by a weighted lever, or by a screw, as shown TO MAKE DRILLS. 333 here. The brace is moved round by the hand of the work- man. Very often this tool is arranged on the vice-bench, BO that the work can be retained in the jaws of the vice while being drilled. Sometimes it is mounted on a separ- ate stand, having a stool below, and a special kind of vice -or clamp is added. Well made, this is not so bad a tool as it looks, but those used ordinarily in smiths' shops are very clumsy, and do not even run true, and the drills are badly made, although by sheer force they are driven through the work. Whatever form of drill-stock is used, the main thing is to have the drills properly formed. You will recognise k and n as common forms, than which m is considerably better. For cast-iron n would not be a bad point, because the angle is great, much greater, you see, than k ; and the bevels which form the cutting edges of a drill should also not be too sharp, as they are generally made, for, as they only scrape away the metal, their edges go directly. The common way to make a drill is this : A piece of steel wire of the required size is heated until red hot (never to a white heat, or it would be spoiled). The end is then flattened out with a hammer, and the point trimmed with a file. It is then again heated red hot, and dipped into cold water for a second. Then held where the changes of colour, which ensue as it cools, can be seen plainly; and at Boon as a deep yellow or first tinge of purple become* 354 THE YOUNG MECHANIC. visible, it is entirely cooled in water. It is tlien finished, except as regards fitting it to the drill-stock, which may be done before or after it is hardened, because care is taken only to dip the extreme point. To get proper cutting edges the drill is taken to the grindstone, and each side of the point is slightly bevelled, but in opposite directions, so as to make it cut both ways. It is not, however, left of equal width, like 0, but the flattened sides are ground away, so as to make more of a point, like p and n. Now, this is all right enough as regards forging and hardening, and tempering, and for the smallest drills this is the only way to make them. (Only watchmakers heat them in the candle till red, and then cool and temper b running them into the tallow.) But if you want a go drill that will cut well and truly, you should file away t". sides of a round bar like , only spreading the point ve slightly indeed, just to prevent the drill sticking fast in t' work. Another drill, indeed, is spoken of very highl which is also carefully made like m, but the places whi^ are here flat are hollowed out or grooved lengthwise, t section of the point i.e., the appearance of the end of ti drill becomes rather curious, like r. I am assured by tin > who have used them, that these cut quite as well as th< twist drills which I have described already. These which I ain now speaking of are also American ; and I don't know* how it is, that somehow America is a far better place foi FLOGGING BY STEAM! 335 improvements in tools and machines than our own Old England. And if I had a wonderful invention a nev birch-rod-making and flogging-machine for very trouble- some boys, for instance I am afraid I should go to America to patent it ; but I daresay English boys would not object to that To teach an idle boy to read, His mind be sure to jog ; But if he 's very bad indeed, You '11 be obliged to flog. Yet if you flog him day by day, He '11 never learn to read ; For boys require a lot of play To make them work with speed. But young mechanics, if they erf Or join the lazy team, Would all, as I suppose, prefer To be well flogged by steam. not, they had better not let me patent my flogging- chine. Luckily it is not invented yet. The cutting edges of drills come under the same rules as ler cutting edges. You might, for instance, hold a large 11 flat on the rest, and use either edge as a turning-tool, u will see at once that these edges will not cut if ade in the usual way, but only scrape. The bevel wanta > be ground only to 3, as before explained, to give he proper clearance, and the cutting edge requires to be then made by grinding back the upper surface, which is just the same in effect as is produced by twisting the metal 336 THE YOUNG MECHANIC. or cutting a spiral groove, which hollows out this upper surface and gives it cutting power. It is no use grinding a sharper-looking bevel, or making more of a point you only weaken the edge ; m or n is quite pointed enough, though the first is a right angle and the second greater ; and, for cast-iron, a rounded point, showing no angle at all, will do just as well, or better, when once it has begun to penetrate. Do not be deceived, therefore, by making drills look pointed and keen, for, I repeat, they are scraping tools only, unless you file an edge by bevelling back the upper face of each side of the point. If you were to make a very thick, strong drill, you might begin by grinding back the two sides to 3, to form the accidental front line of the point or section angle, and then grind back, at 45 'from this line, the upper face, by which you would do just what you did to give the graver cutting edges of 60 only a drill thus formed must have a point of 90. It would cut in tw^ directions, like one for a drill stock and bow. 1 hope my bigger boys will not pass over the remarks on cutting edges interspersed in this book, for, once under- stood, they will be found to be most valuable. Indeed, they cannot work intelligently until they understand exactly the nature and principles of the tools which they have to use. In drilling iron, use water or oil, or soap and water, or soda-water either will do; but the holes are drilled in the ships' armour-plating with soap and water to cool the DRILLS AND BORING-BITS. 337 drill ; and very well it answers, for these plates are several inches thick, but the holes are soon made. When working in brass and gun-metal, use no water, but work the drill quite dry. The same rules, in short, apply to drilling as to turning or planing metal ; and if you could see the action of a well-made American twist-drill, you would re- cognise this similarity, for you would see the metal come forth in long, bright curls, as pretty and shining as those of your favourite young lady or loving sister one of which you have, I daresay. To give you some idea of what a straight course a drill will take, if rightly made and skilfully used, I may tell you that a twist-drill has been run through a lucifer-match from end to end without splitting it ; and as to the fineness possible, I have seen a human hair with an eye drilled through it, by which, needle-like, it was threaded with the other end of itself. I told you how to bore a cylinder, which is but drilling on a larger scale, and in Fig. 65 I sketched the method of doing this in the lathe with a rosebit. But I did not ex- plain another tool used just in the same way, but which will bore holes in solid iron wonderfully. Fig. 65, L, H, K, is one of these. This is an engineer's boring-bit, and is made of all sizes, from that required to bore the stem of a tobacco- pipe (don't smoke, boys, it will dry up your brains) to that which would bore a cannon. A rod of steel is forged Y 3 3 8 THE YOUNG MECHANIC. with a boss or larger part at one end. This is centred in the lathe, and the centre-marks are well drilled, and not merely punched, especially that at the small end. The boss is then turned quite cylindrical, after which it is filed* away exactly to the diametrical line, as you will see by inspection of L. The end is then ground off a little slanting, to give, as before, about 3 of clearance. The cutting edge thus ob- tained, and the end in which the centre hole still remains, are carefully hardened. You thus have a tool which will bore splendidly, but you must give it entrance by turning a recess first of all in the work, or drilling, with a drill of equal size, a little way into the material. Used like the rosebit, this tool will run beautifully straight, so that you can bore very deep, long holes with it, and cylinders can be most beautifully bored with it. I think you would be able to make these tools with a little care ; but, when you harden them, only heat and dip the extremities, or it is ten to one your steel rod will bend and warp in cooling, and you will not be able to rectify it. If the ends are quite hard, it is as well that the rest should be soft, as the tool will not then be so liable to get broken. There are many other tools used for boring iron and steel, but you need not trouble yourself at present to learn any- thing of them they are no use to you now. I have headed this chapter " Hardening and Tempering " * In large tools this is not done by the file. OXYGEN. 339 tools, but as yet I have only partially explained the process, which is a very curious one ; and though the result is highly necessary in many cases, it is by no means well understood what really takes place in the process, or why this effect should occur in steel, but not in iron, or brass, or other metals. If you heat a piece of bright steel over a clear gas jet or fire which will not smoke it, you will see several colours arise as the metal gets hotter and hotter, until finally it becomes red. These are due to oxidation, which is so long a word that I am not sure I can stop to explain it thoroughly. Let us see, however, what we can make of it. The air we breathe contains two gases, oxygen and nitrogen, with a small proportion of a third called carbonic acid. Neither of these alone will support life, or keep the fire burning, or enable vegetables to live and grow, but it is the first which is in this the chief support. The second is only used by Nature as we use water to brandy, viz., to dilute it and render it less strong. If we breathed oxygen alone, we should live too fast, and wear out our bodies in a few hours. If we breathed nitrogen only, we should die, and so of car- bonic acid. Now this oxygen seizes upon everything in a wonderful and sometimes provoking manner. If you leave a bright tool out of doors to get damp, down comes our friend oxygen and rusts it. It combines with the'iron and makes oxide of iron, which is what we call rust. I suppose, 340 THE YOUNG MECHANIC. however, this oxygen comes more from the water than the air, hecause water is made also of two gases, hydrogen and this same oxygen. It is certain that oxygen in this case always finds any bright tools that we leave about in the wet, and coats them with a red jacket very speedily. Then if you look at a blacksmith at work, you will see scales fall from the hot iron as he hammers it. These are black, but our old friend has been at work, and united with the red- hot metal and formed another oxide of iron, called black oxide. We can understand this. If a man eats a good deal, or drinks a good deal, he gets red in the face ; if he eats till he chokes himself, he gets black in the face, and I sup- pose it is much the same when oxygen eats too much iron. Well, when we begin to heat the steel, down comes oxygen and begins his work ; and first he looks very pale ; then he gets more bilious and yellower ; then he gets hotter and shows a tinge of red with the yellow forming orange ; then he begins to get purple, then blue, then deeper blue ; and finally black before he gets absolutely red and white hot. Now to temper steel, we first heat it red-hot, not mind- ing these colours, and then we cool it suddenly in cold water. This renders it very hard indeed. No file will cut it, or drill penetrate it ; but if we strike it, behold it breaks like glass ! This is too hard for general work, for the edge will break and chip if it meets with any hard spot in the metal, or chances to bite in too deep. Its teeth are too brittle, and TEMPERING. 341 so get broken off. For this reason we have to " let down," or temper, the tool, and we proceed as follows : The part to be tempered is ground quite bright. It is then laid upon a bar of iron heated red-hot, or if small, it is held over a gas jet or in a candle ; heated, in short, in any way most suitable and convenient. And now, first, our friend oxygen puts on a pale yellow face as before. This will do for turn- ing steel and iron, but is still too hard for general work. Then comes the orange, and this presently tends slightly to blue ; at which point, if the tool is instantly cooled in water, it will be found to bear a good edge, hard, but sufficiently tough for work. Most tools for metal and drills are let down to something between the yellow and blue, and we know that the more they approach blue, the softer they will be. Thus we can easily manage OFJ tools ; some to bear hard blows, like axes, which are tampered to a blue colour ; some like files, which a blow will break, but which are famous for their own special work these are let down only to a pale yellow; others, like springs and saws, are let down to a more thorough blue, because they are required to be elastic and tough, but are not needed to be so par- ticularly hard. Then tools like turnscrews, and bradawls, and gimblets are left even softer, sometimes not tempered or hardened at all, but just forged and ground to the re- quired shape. Now, I fancy some of my sharp boys will say that the 34* THE YOUNG MECHANIC. first description I gave of the mode of hardening and tem- pering was not exactly like this; nor was it, yet in principle it is the same. For instance, if you give a drill to a smith to make, he will do as I then said. He will heat the extreme point red-hot, then dip the point in water, give a rub on the stone or bricks of the forge, and watch the colours. This can be doiie when the tool is of sufficient substance to retain heat enough after the edge has been dipped to re-heat that edge sufficiently. In this case there is no need to chill the whole tool and then heat it again. But in the case of small drills and tools, pen- knife-blades, and other articles of this nature, there will not be sufficient heat retained, after dipping, to bring up to the surface the desired colours ; for oxygen likes a hot dinner as well as you do, and if the iron is not hot enough he will have nothing to do with it. One great difficulty you would find if you had much tempering to do, viz., that the articles bend under the operation, some more than others. Try this : Take a thin knitting-needle when the owner is not looking, and run off with it ; it is all in the cause of science ! Heat it red-hot, and with a pair of pliers take it up and drop it sidewise in a basin of water. It will bend like a bow. Heat again, straighten it, re-heat, and thie time pop it in lengthwise endwise, point first I mean (don't you see that a round needle has no sides, and puts me into a perfect quagmire DURING HARDENING. 343 of difficulty). However, you will understand this, and will find the needle not bent nearly so much as before, but still it is not straight. As I explain most things as I go on, I may as well explain why this bending occurs before I tell you how to straighten your work again. All metals expand with heat, and contract with cold. I am sure 1 contract terribly in the winter until I have had plenty of hot soup, and hot roast-beef, and plum-pudding ; and I know my tempei improves, too, when I get expanded and warm. Well now, when you dropped your sister's knit- ting-needle all hot on its side into the water, that side contracted before the other, and consequently the needle bent ; but when you put it in the water, end on, it was cooled all round at once, and if you could but cool a piece of metal equally all over, inside and out, at once, all parts would shrink equally fast, and the article would remain straight. But there is, unfortunately, another cause of this bend- ing, which is, that all articles are not of such form that the same quantity of metal is on all sides of the axial line. Take a half-round file, for instance; one side is flat, the other curved, so that taking these two surfaces into consideration, one contains a great deal more metal than the other, and will not cool at the same rate. These articles are far more liable to bend than those whose sides are parallel. Another result of the hot mass being cooled most quickly on the outside is, that cracks are produced in $44 THE YOUNG MECHANIC. the latter, because, so to speak, the skin is contracted, and can no longer contain all the expanded metal within it. Hence, to make a mandrel for a lathe, it is common to bore it out first, before hardening, to remove this mass of metal, and to allow the water to touch it inside as well as out. Such mandrels seldom crack or bend. The only way to straighten articles which have warped by hardening, is by what is called hacking or hack-ham- mering, which is nothing more than hammering the con- cave or hollow side with the edge of the steel pane of a hammer. This spreads the metal upon the hammered side> and, by expanding it, straightens the tool, for the hollow- side, remember, is that which was too much shrunk or con- tracted. This is not an operation you will have to do, especially if you only harden the extreme points of the drills and httle tools you make. There is another way of hardening, not steel, but iron r called tl cate hardening," because it puts a case of steel over the surface of the metal. Obtain a salt called prus- siate of potash. It is yellow, like barley-sugar, but is poison. Heat the iron red-hot, and well rub it upon this salt, and then cool it in water. You will find that now a file will not touch it, its surface being as hard as glass. It is carbonised on its exterior, and made into hard steel. This can be done in another way, as gun-locks, snuffers, and many o\ her things are case hardened. The} are en- KING'S COLLEGE SOYS. 345 closed in an iron box, with cuttings of leather and bone- dust, and the box is luted about with clay and put in the fire. All the pieces get red-hot, and the leather chars and blackens, and some of it combines as before with the hot iron, and makes it into steel. And our friend oxygen is considerably at a loss in this case to find his way in, or he would make black scales again and spoil the work ; or com- bine with the carbon (or charcoal) and make it into gas. Probably, however, as we shut up a little oxygen with the contents of the box, this change DOES take place, "but Just as the gas rises the iron seizes it, and holds it fast. And now, boys, I find it necessary to lay down the pen, which I see has almost run away with me, and written a good many more pages than I at first intended. Since I began to write I have visited the workshops at King's College, and seen a sight to gladden my eyes. Boys car- pentering, boys turning, boys filing ; engines of real use, with single and double cylinders, finished, and in course of construction, and all these the work of schoolboys, whose hands and brains are alike engaged in this delightful branch of industry. Let no one, therefore, pretend that boys are not capable of executing good work of this kind in a masterly manner, or that what they do is always child's- play, or I shall take up the cudgels in their behalf. I have also seen, in the Working- Men's Exhibition, a very neat little engine, made by a boy only twelve years of age, z 34i". '1HE YOUXG MECHANIC. which makes me hope and believe that the few hints upon wood and metal work which I have here thrown together will neither be unacceptable nor useless to those whom I address in these pages. In this hope I take my leave, and gign myself, with gratification and pride The boy mechanic's faithful friend, THE AUTHOR, of the Battens. EDITED BY EVELYN ABBOTT, M.A., FELLOW OF BALLIOL COLLEGE, OXFORD. A SERIES of biographical studies of the lives and work of a number of representative historical characters about whom have gathered the great traditions of the Nations to which they belonged, and who have been accepted, in many instances, as types of the several National ideal; With the life of each typical character will be presentee a picture of the National conditions surrounding him during his career. The narratives are the work of writers who are recog nized authorities on their several subjects, and, while thoroughly trustworthy as history, will present picturesque and dramatic "stories " of the Men and of the events con- nected with them. To the Life of each " Hero " will be given one duo- decimo volume, handsomely printed in large type, pro- vided with maps and adequately illustrated according to the special requirements of the several subjects. The "olumes will be sold separately as follows : loth extra $i 50 falf morocco, uncut edges, gilt top- . . 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