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 A 
 
 TEXT BOOK 
 
 OF 
 
 MECHANICAL DRAWING 
 
 PART III. 
 
 MACHINE DRAWING, 
 
 BY 
 
 Gardner C. Anthony, A. M., 
 
 PROFESSOR OF DRAWING IN TUFTS COLLEGE ; 
 
 DEAN OF THE BROMFIELD-PEARSON SCHOOL ; 
 
 MEMBER OF AJVIERICAN SOCIETY OF MECHANICAL ENGINEERS.
 
 Copyright, 
 By Gardner C. Anthony, 
 1893.
 
 Anno)( 
 5U158i6S 
 
 PREFACE. 
 
 This treatise is inteiuled to teach the practical application of the principles of projection to 
 the illustration of machinery ; to inform the student concerning many of the exceptions to the 
 laws of projection ; and finally, to furnish such practical examples as may serve for problems to 
 the student, and suggestions to the draftsman. It aims to encourage a concise graphic expression 
 in the colloquial phrases of modern mechanical drawing, instead of the more classic language 
 which would enforce a rigid adherence to the laws of projection, and the customs of several 
 centuries of architectural draftsmen. 
 
 The examples chosen are those which, being faithfully and intelligibly executed, will enable 
 the student to acquire much practical information on the subject by the making of only a few 
 drawings. The number of subjects suitable for these exercises is surprisingly small ; for at this 
 period of the student's advancement, it is the art of graphic expression rather than that of drawing 
 which is most required, and this cannot be attained by the making of copies. It is, indeed, almost 
 a waste of time to copy a drawing, since proficiency in penciling may be better acquired by other 
 means, and tracing is much superior as an exercise in inking. The difficulty in obtaining suitable 
 models has, however, necessitated much of this, but it is hoped that the present volume may assist 
 in obviating the trouble by supplying such problems as may lead the student to observe closely, 
 think accurately, and express clearly. The subjects chosen for the exercises are such as have been 
 found suitable for illustrating most of the principles taught as well as the practical suggestions 
 made in this book. 

 
 Iv 
 
 PKEFACE. 
 
 Much care has been exercised in the making and figuring of these drawings, that they should 
 be complete and correct ; but tliat this should be realized in every detail, is more than tiie author's 
 experience would lead him to expect. While it is to be desired that the one great lesson of 
 accuracy should be emphasized above all others, it is also to be remembered that draftsmen are 
 not infallible, and it is the minimum rather than the absence of mistakes by which we are to judge. 
 
 As this book is tlie advocate of no special systems of lining, figuring, lettering, etc., the 
 plates will be found to represent a variety of types in drawing which may at some time serve the 
 draftsman who is not bound to special methods but seeks the one and only end to be attained, 
 namely, the art of using all available instrumentalities in securing a terse, accurate, and complete 
 expression of mechanical ideas. 
 
 Gardner C. Anthony. 
 
 Tufts College, Mass., Oct. 2, 1893.
 
 CONTENTS. 
 
 CHAPTER I. 
 
 The Representation of Bolts and Screws. 
 
 screw threads. 
 
 U. S. Standard Screw Threads, 2 ; Table of the Strength of Screw Threads, 4 ; Table of Decimal 
 Equivalents, 5 ; Representation of V Threads, tj ; Square Threads, (i ; Buttress Thread, 7. 
 
 BOLTS AND SCREWS. 
 
 U. S. Standard Hexagonal Head and Nut, 8; Check-nuts and Washers, 10; Square Heads and 
 Nuts, 11; Set-screws, 12; Cap-screws, 13; Round Head Screws, 13. 
 
 CHAPTER n. 
 
 General Rules for the Making of Working Drawings. 
 
 Introduction, 14; Classes of Drawings, 16; Size of Sheet, 16; Lay-out of the Drawing, 17; 
 Number and Arrangement of Views, 17 ; Scale to be Used, 18 ; Method of Penciling the 
 Drawing, 19 ; Method of Inking, 20 ; Shade Lines, 20 ; Line Shading, 21 ; Title, 23.
 
 vi CONTENTS. 
 
 CHAPTER III. 
 
 SECTIONAL VIEWS. 
 
 Use of a Section, 24 ; vSection Liners, 24 ; Notation for Section Lining, 25 ; Dotted Sections, 26 ; 
 Colored Sections, 28 ; Choice of Cutting Planes, 2^ ; Broken Sections, 32. 
 
 FIGURING. 
 
 Methods considered, 32; Rules to be observed, 34; Finding Dimensions, 36; Finished Sur- 
 faces, 36. 
 
 TECHNICAL SKETCHING. 
 
 Value and Methods of Practice, 37 ; Order to be observed in the making of a Sketch, 38 ; Practi- 
 cal Observations, 39 ; Sketch Books, 40. 
 
 CHAPTER IV. 
 Examples for Practice. 
 Problem 1. Assembled Drawing of a Locomotive Parallel Rod, 4L 
 
 2. Assembled Drawing of a Boiler Check Valve, 42. 
 
 3. Detailed Drawing of a Globe Valve, 42. 
 
 4. Connecting Rod, 42 ; Method of determining the curves of intersection, 42 ; Action 
 of Gib and Key, 44 ; Assembled Drawing of a Connecting Rod, 45. 
 
 5. Detailed Drawing of a Back Rest, 46. 
 
 6. Assembled Drawing of a Screw Polishing Machine, 47. 
 
 7. Detailed Drawing of a Crosshead, 47. 
 
 8. Detailed Drawing of the Tail Stock of a 17" Lathe, 48. 
 
 9. Assembled Drawing of the Head Stock of a 16" Lathe, 48,
 
 CHAPTER I. 
 Bolts and Screws. 
 
 The representation of bolts, nuts, screws and screw-threads, is of such importance that a 
 thorough knowledge of their proportions, and the conventional method of illustrating them, is of 
 the first consideration to the machine draftsman. Printed tables of the dimensions of bolt-heads, 
 nuts, set-screws, etc., are usually published in connection with treatises on machine design, but it 
 is far better for the student of machine drawing to fix the proportions of the various parts in his 
 mind, and learn to judge for himself of their comparative value. In the present treatise, only the 
 more common types will be illustrated, and it is assumed that the student is already familiar with 
 the theory of the helix and its application to the various forms of screw-threads, as well as the 
 drawing of an hexagonal bolt-head and nut.* In the study of the following pages the student is 
 recommended to so master each type that he may rapidly draw or sketch the bolt or screw with its 
 proper proportions, having only the diameter of the thread given. 
 
 * For a complete t^c■ilti^^e on the helix and its applioation to the drawing nf screw-threads, together wiih the construction of the 
 hexagonal holt-head and nut, see Part II. of this series.
 
 SCREW-THREADS. 
 
 Scuew-Thkeads. 
 
 The form of screw-thread commonly used, is tliat of the U. S. Standard, also known as the 
 Franklin Institute Standard, and illustrated by Fig. 1. The proportion of pitch to diameter is 
 
 P=0.24i D 4-0. 625-0. 175. The depth of the thread [S] is 0.65 P. 
 While the pitch in single threaded screws is, properly speaking, the 
 distance between consecutive threads, the term is often applied to the 
 number of threads per inch. Thus a screw having eight threads to 
 an inch is frequently spoken of as 8 pitch. Although this is obviously 
 wrong, yet it leads to no confusion, since the pitch, and the number 
 of threads per inch, are reciprocals of each other. The flattening of 
 the thread, as indicated in the figure, is for the purpose of preventing 
 injury to the thread by the bruising of the otherwise sharp V. In 
 the following table the proportions of this thread are given for bolts 
 from i to 4 inches in diameter. To this is also added the tensile 
 strength of the screw when subjected to varying stresses. 
 
 Column 1 gives the outside diameter of the thread. 
 
 Column 2 gives the number of threads per inch, the pitch being 
 the reciprocal of this number. 
 
 Column .3 gives the diameter at the root, or bottom of thread. 
 This is important in obtaining the diameter of the tap drill, which is 
 approximately given in the next column. 
 
 Fig. I ^^ge -^ 
 
 LEFT HAND 
 
 RIGHT HAND 
 
 FiG.2
 
 SCREW-THREADS. 
 
 i 
 
 Column 4 gives the diameter of drill to be used for any given diameter of thread or tap. It 
 will be noticed that these sizes are a trifle larger than the diameters at root of thread. 
 
 Columns 5, fi, 7 and 8 are of special value to the machine designer, but are introduced here to 
 enable the student to obtain some appreciation of the strength of the V thread. The weakest 
 part being at the root, its strength will be dependent on the diameter of this part and the tensile 
 strength of the material. In the case of a screw of U inch diameter, the diameter at the root is found 
 in column 3 to be 1.065, the area of which is .78. If it is required that 4000 lbs. be the strain 
 to which every square inch is subjected, then will the thread sustain .78 times 4000 lbs. which 
 is 3120 as given in column 5. In this manner the table is constructed for four, five, six and 
 seven thousand pounds tensile strength. A valuable application of this table is in determming 
 the size of a screw, having given the total load to be sustained and the permissible strain per 
 square inch. Suppose it is required to obtain the diameter of a bolt sufficient to overcome a re- 
 sistance of 32000 lbs. and to be strained to only 4000 lbs. per square inch. In column 5 is 
 found the number 33000, which is the nearest to the required amount. Against this number, in 
 column 1, is seen SJ, which is the necessary diameter of screw. If, however, the allowable strain 
 per square inch had been 7000 lbs. a screw of 2f inch diameter could have been used. 
 
 In connection with this table, one of decimal equivalents is also published. The student 
 should not be dependent on this for the equivalents of eighths and sixteenths of an inch, as they 
 may be so easily memorized and are of such frequent use.
 
 SCREW-THREADS . 
 
 U. S. STANDARD THKEAD. 
 
 Diame- 
 ter of 
 Scifw. 
 
 Threads 
 
 per 
 
 luch. 
 
 Diameter 
 
 at root of 
 
 Thread. 
 
 Diame- 
 ter of 
 Tap Drill 
 
 Tensile | Tensile 
 Strength at;Strcngth at 
 4000 lljs.per 60OO Ihs.per 
 
 sq. Inch. sq. Inch. 
 
 Tensile | Tensile 
 
 •Strength at Strength at 
 
 eoooibs. perTOOOlbs.per 
 
 sq. Inch. sq. Inch. 
 
 1 
 
 4 
 
 20 
 
 .185 
 
 A 
 
 107 
 
 134 
 
 161 
 
 187 
 
 ^ 
 
 18 
 
 .240 
 
 L 
 
 181 
 
 226 
 
 271 
 
 316 
 
 s 
 
 16 
 
 .294 
 
 A 
 
 271 
 
 339 
 
 407 
 
 475 
 
 -;v 
 
 14 
 
 .344 
 
 23 
 
 371 
 
 465 
 
 558 
 
 650 
 
 i 
 
 13 
 
 .400 
 
 Yi 
 
 500 
 
 625 
 
 750 
 
 875 
 
 A 
 
 12 
 
 .454 
 
 15. 
 
 647 
 
 809 
 
 971 
 
 1133 
 
 a 
 
 11 
 
 .507 
 
 1^' 
 
 784 
 
 980 
 
 1176 
 
 1372 
 
 3 
 
 10 
 
 .620 
 
 R 
 
 1200 
 
 1500 
 
 1800 
 
 2100 
 
 I. 
 8 
 
 9 
 
 .731 
 
 4 
 
 1680 
 
 2100 
 
 2520 
 
 2940 
 
 1 
 
 8 
 
 .8157 
 
 li 
 
 2200 
 
 2750 
 
 3300 
 
 3850 
 
 u 
 
 7 
 
 .940 
 
 2760 
 
 3450 
 
 4140 
 
 4830 
 
 ll 
 
 7 
 
 1.065 
 
 1,^- 
 
 3120 
 
 3900 
 
 4680 
 
 5460 
 
 IS 
 
 6 
 
 1.160 
 
 lA 
 
 4240 
 
 5300 
 
 6360 
 
 7420 
 
 u 
 
 6 
 
 1.284 
 
 13^2 
 
 5120 
 
 6100 
 
 7680 
 
 8960 
 
 1§ 
 
 5\ 
 
 1.389 
 
 isi 
 
 eiL'O 
 
 7650 
 
 9180 
 
 10710 
 
 H 
 
 5 
 
 1.491 
 
 n 
 
 7040 
 
 8800 
 
 10560 
 
 12320 
 
 H 
 
 5 
 
 1.616 
 
 n 
 
 8120 
 
 10150 
 
 12180 
 
 14210 
 
 2 
 
 4i 
 
 1.712 
 
 ^ 
 
 9200 
 
 11500 
 
 13800 
 
 16100 
 
 2i 
 
 4i 
 
 1.962 
 
 2 
 
 12480 
 
 15600 
 
 18720 
 
 21840 
 
 2J- 
 
 4 
 
 2.176 
 
 2A 
 
 14800 
 
 18500 
 
 22200 
 
 2.5900 
 
 2iJ 
 
 4 
 
 2.426 
 
 2.^6 
 
 18400 
 
 23000 
 
 27600 
 
 32200 
 
 3 
 
 3!> 
 
 2.629 
 
 2j!, 
 
 217(;u 
 
 27200 
 
 32K4U 
 
 38080 
 
 3V 
 
 31 
 
 2.879 
 
 2U 
 
 26400 
 
 33000 
 
 39600 
 
 46200 
 
 Sk 
 
 3} 
 
 3.100 
 
 H' 
 
 30160 
 
 37700 
 
 45240 
 
 52780 
 
 3J 
 
 3 
 
 3.317 
 
 Hh 
 
 34400 
 39600 
 
 43000 
 
 51600 
 
 60200 
 
 4 
 
 3 
 
 3.567 
 
 
 49500 
 
 594U0 
 
 69300
 
 SCBEW-THRKADS . 
 
 DECIMAL EQUIVALENTS. 
 
 Fraction. 
 
 Decimal. 
 
 Fraction. 
 
 Decimal. 
 
 Fraction. 
 
 Decimal. 
 
 Fraction. 
 
 Decimal. 
 
 tV 
 
 .015625 
 
 .03125 
 
 .046875 
 
 
 .265625 
 
 .28125 
 
 .296875 
 
 If 
 
 .515625 
 
 .53125 
 
 .546875 
 
 u 
 
 2 a 
 SS 
 
 u 
 
 .765625 
 
 .78125 
 
 .796875 
 
 .0625 
 
 5 
 
 .3125 
 
 tV 
 
 .5635 
 
 H 
 
 .8125 
 
 8 
 
 .078125 
 
 .09375 
 
 .109375 
 
 11 
 
 II 
 
 .328125 
 
 .34375 
 
 .359375 
 
 
 .578125 
 
 .59375 
 
 .609375 
 
 
 .8281<;5 
 
 .84375 
 
 .859375 
 
 .125 
 
 3 
 S 
 
 .375 
 
 5 
 
 8 
 
 .625 
 
 i 
 
 .875 
 
 
 .140625 
 
 .15625 
 
 .171876 
 
 ft 
 
 u 
 
 .390625 
 
 .40625 
 
 .421875 
 
 U 
 
 .640625 
 
 .65625 
 
 .671875 
 
 ii 
 II 
 
 .890625 
 
 .90625 
 
 .921875 
 
 A 
 
 .J 875 
 
 A 
 
 .4375 
 
 H 
 
 .6875 
 
 n 
 
 .9375 
 
 .203125 
 
 .21875 
 
 .234375 
 
 
 .453125 
 
 .46875 
 .484375 
 
 II 
 
 .703125 
 
 .71875 
 
 .734375 
 
 .953125 
 
 .96875 
 
 .984375 
 
 1 
 
 4 
 
 .25 
 
 '2 
 
 .5 
 
 3 
 
 4 
 
 .75 
 
 1 

 
 FiG.3 
 
 SCREW-THREADS. 
 
 Representation of V Threads. — It is very rarely that a 
 thread would be shown as in Fig. 1 and seldom as in Fig. 2, since 
 the labor of drawing the V is very considerable. The best conventional 
 method of representing the V thread is shown by Fig. 3, although that 
 of Fig. 4 is much used. The objection to the latter form is in tlie 
 greater length of the heavy lines which obscures more of the drawing, 
 often making too little space for the figures. It is rarely necessary to 
 draw the exact number of threads per inch, required by the table; in- 
 deed the representation is usually clearer when a less number is used, 
 and the drawing of unnecessary lines is also saved. If it is of importance 
 to specify tiie pitch, it is best done by Roman numerals, indicating the 
 number per inch. A double thread is shown by Fig. 5, for the pur- 
 pose of calling attention to the difference between it and the single 
 thread. The character of the double thread is better shown by Fig. 6. 
 Fig. 4 in the case of a dotted thread, economy in the use of lines is of still 
 
 greater importance, and the V alone is often shown as illustrated by 
 Fig. 17 or in a practical drawing by the cross-head pin, and gib set- 
 screws of Plate 10. 
 
 Square Threads. — In Fig. 7 three forms of the square thread are 
 represented. To the right is the section showing the proportion of pitch 
 to depth of thread. In the middle is drawn the more correct conven- 
 tional representation, and on the left is the simple form commonly used. 
 In the latter it will be observed that the inner helix is omitted and in 
 
 Fig. 5
 
 SCRE\V-TH HEADS. 
 
 this type of screw it is also better to draw the exact number of threads 
 required, except the scale be small or the pitch very fine. 
 
 Buttress Thread.— Fig. 8 illustrates a third type which is 
 sometimes known as a ratchet thread. It is used for imparting motion 
 but only in cases where the strain is in one direction, as in a screw jack. 
 By this means the friction is reduced, while the strength of the V thread 
 is maintained. There is no standard for this thread, but the usual form 
 and proportion is that shown by the figure. 
 
 Bolts and Screws. 
 
 Save for the hexagonal bolt-head, there is no generally accepted 
 standard for the heads of bolts and screws. For the draftsman it is 
 essential however, that some system be used in the illustration of forms 
 which occur so frequently as do these. The time required to properly 
 design the head of a bolt, set-screw, or other fastening device, is very 
 considerable, and to have done it once should suflice. When a definite 
 form of head is required it should only be necessary to produce the 
 same according to certain proportions already fixed, and obtainable 
 either from a ready reference table or, better still, from memory. As it 
 is generally unnecessary to give all the dimensions of the head or nut on 
 the drawing, it is immaterial whether the representation conforms exactly 
 to the finished size or not. It is therefore a useless delay for the drafts- 
 
 OOUBLE THREAD 
 
 -c-P-A-F 
 
 Fig. 6 
 
 Fig. 8
 
 BOLTS AND SCREWS. 
 
 r^^^3^^^«Tsrtv 
 
 man to spend any more than time enough to produce the desired type of 
 head according to his standard. The following proportions are suggested 
 from standards already in use by many shops. 
 
 U. S. Standard Hexagonal Head and Nut. — Two types of 
 head and nut are illustrated, the rounded or spherical Figures 9, 10, 
 11, and chamfered or conical Figures 13, 13, 1-1. In general 
 the chamfered head is used for sketching, for rough work and when- 
 ever a special finish is not required. The rounded head, which pre- 
 sents a more finished appearance, is used almost exclusively for the heads 
 and nuts of bolts for finished machinery. Three dimensions only are 
 fixed by the Government standard, viz., the distance across flats, or short 
 diameter, commonly marked H and equal to one and one-half times the 
 diameter of the bolt, plus one-eighth of an inch. Second, the thickness of 
 the head, equal to one-half the short diameter. Third, the thickness of 
 nut, which is equal to the diameter of the bolt. 
 
 In the following suggestions for the drawing of hexagonal heads 
 it should be remembered that the rounded type is a sphere cut by six 
 planes parallel to the axis, while the chamfered head may be considered as 
 a cone similarly cut. 
 
 Fig. 1). — Having determined H or the short diameter and drawn 
 the edges, lay off the thickness of head and describe the top with a radius 
 of twice the diameter of bolt. To obtain the arc ABC, determine point 
 B which is equal in hight to K, and through it describe the required arc
 
 BOLTS AND SCREWS. 
 
 with radius equal to M N, using care to have C and A of same hight. 
 The fine dotted lines show the precise method of finding these points by 
 obtaining the long diameter. 
 
 Fig". 10. — Figure the short diameter and obtain the long diameter 
 geometrically as shown by the dotted lines. [In small bolts, or drawings 
 to small scale the long diameter may be made equal to 2 D.] The edge 
 SL is equidistant from VW and the center line, and equal to V AV in 
 lensth. Throudi S describe arc O R S concentric with curvature of top. 
 Tiu-ough S and V describe arc S E V with radius equal to L W. 
 
 Fig. 11. — This differs from the preceeding only in that the thick- 
 ness is equal to the diameter of the bolt. Observe also that the curvature 
 of the top begins at G instead of on the center line. 
 
 Figures 13, 13, and 14-. — In drawing the chamfered head or 
 nut across corners, as in Figures 12 and 14, describe ABC tangent 
 to top with radius equal to diameter of bolt. From the same center 
 describe arc E F, point F being equal in hight to C. 
 
 Heads and nuts drawn in connection with the parts which they unite 
 should in general be shown across corners. This will prevent errors in 
 the allowance to be made for hubs, washers, etc., as it gives the maximum 
 space required for the head. The necessity for observing this is at times 
 80 great that the bolt is required to be drawn across corners in all views 
 in which it may appear. In sketcliing bolts and in the making of bolt 
 lists it is better to represent them across flats, as they are both more easily 
 drawn^and figured. 
 
 Fig. 1 2 
 
 Fig. 13 
 
 Fig. 14
 
 10 
 
 BOLTS ANJ) SCREWS. 
 
 Fig. 15 illustrates a bolt with check-nuts and washers. It is a common practice to make 
 both nuts of the same thickness and equal to three-quarters of the diameter of the bolt. The 
 more proper form, however, is to make the thickness of the nut sustaining the load equal to the 
 diameter of bolt. Observe also that the outer nut is chamfered on both faces. This might be 
 done in all cases, but polished parts united by bolts having heads and nuts so chamfered, are not 
 
 -^ 
 
 ^ 
 
 hi 
 
 T 
 
 L LENGTH 
 
 F,G.I5 ' «^'<^16 
 
 so easily wiped, since the oil and dust is likely to lodge under the corners. The necessity for 
 chamfering the outer faces is very great, as otherwise the sharp corners would cause difficulty in 
 handling and soon become marred. 
 
 When a tapped hole is extended for some length beyond the end of the screw or bolt, as in 
 Fig. 16, it is better not to draw the threads in this portion if the piece tapped be in section. But 
 if a tapped hole be shown in a section then the threads may be shown as at A, Fig. 17. Dotted 
 representations of the same thread are shown by B and C.
 
 BOLTS AND SCREWS. 
 
 11 
 
 The end view of a tapped hole is often illustrated by the drawing of two circles in order to 
 distinguish it from a drilled hole. In such cases the outer circle is made equal to the diameter of 
 the thread. 
 
 The length of a bolt is measured from the underside of the head to the end, unless the end be 
 
 
 Fig 18 
 
 part only, as in Fig. 18. The length of 
 
 rounded, in which case it is usual to figure the straight 
 the thread must of course be figured from the end. 
 
 Square Headed Bolts, Nuts and Screws. 
 usually observed for the square also, save in the radius 
 to be two and one-half diameters. 
 
 Fig-. 18 The arc A B C is concentric with the top and is described through the point B 
 
 which is equal in hight to E, In drawing the head or 
 
 -The proportions for hexagonal heads are 
 for the curvature of the top, which is better 
 
 nut across corners the geometrical method
 
 12 
 
 BOLTS AND SCREWS. 
 
 may be used as shown, remembering that F G is equal to half the short diameter, and F K half 
 the long diameter. Or the long diameter may be made equal to one and one-half the short 
 diameter in small bolts, or where accurate work is not required. 
 
 LUgJ 1 
 
 Fig. 20 
 
 FiG.21 
 
 
 
 "f 
 
 
 
 (M 
 
 1 
 
 
 
 1 
 
 b 
 
 
 
 Fig. 22 
 
 Set-screw, Fig. 19. — The construction of this will be apparent from the figure on which 
 the proportions are given. Of course it is unnecessary to draw the top view as the distance marked 
 A can be estimated by the eye. The radius for the point of a set-screw should be four diameters. 
 
 Fig'uve.s yO, 31 aii<l 'i'i represent three other types of screws having square heads. In the 
 gib-screw Fig. *-il, the [troportion adopted for the short diameter is also excellent for the squaring 
 of the end of any rod, as must frequently be done for a box wrench, Fig. 33.
 
 BOLTS AND SCREWS. 
 
 13 
 
 Cajj-screw, Fig. 33. — This is an excellent type for many purposes where a small diameter 
 of head is required. The extra length of the head makes it especially suitable for places where 
 frequent adjustment is needed. 
 
 Hound Head Screws, Figures 33 and 34. — These differ only in depth of head and 
 
 <HD]- 
 
 f 
 
 Fig'. 23 
 
 — »— I— ,-i _l X 
 
 hA+o-J S 
 
 Fig. 24- 
 
 FiG.25 
 
 finish of end. The type of Fig. 35 being better adapted for countersunk work, since a variation 
 in the depth of the hole will not effect the appearance of the fit as would be the case in that of 
 Fig. 34. In representing the end view of a slotted head, always draw the lines of the slot at an 
 anfle of 45 decrees, thereby making greater contrast with other lines of the drawing and thus pre- 
 
 venting confusion. 
 
 The figured length of these screws should always include the head.
 
 CHAPTER II. 
 
 General Rdles for the Making of a Working Drawing. 
 
 introduction. 
 
 Drawing is a graphic language, and may best be studied by subjecting its use to laws similar 
 to those governing other languages. Like others, it has its orthography, grammar, and litera- 
 ture. Its orthography, consisting of the various types of lines, its grammar being the art of repre- 
 senting objects upon planes, and known as orthographic projection ; and finally its literature, con- 
 sisting of the practical application of these principles to the drawings which we are required to 
 read and write. But in this, as in all languages, we cannot be governed entirely by laws, but 
 must familiarize ourselves with the idioms and conventional methods of our day, remembering 
 always that it is simply a medium for the expression of our thoughts. 
 
 A drawing fulfills its object only when it clearly sets forth the ideas to be expressed, and in 
 nowise misleads the reader to whom it is especially addressed. If it fails to do this, it is a poor 
 drawing, regardless of the fact that it may conform to all established laws and be executed with 
 the greatest precision and elegance. A drawing should be regarded as a business letter to the 
 mechanic, and must first of all be brief, having as few lines and figures as possible. It must 
 completely express the idea, omitting no lines or views necessery to attain this end. It must 
 contain nothing that may mislead, even though it be to violate the laws of projection. The char- 
 acter of the drawing must be determined by the use to which it is put. If a free-hand sketch is
 
 INTRODUCTION. 15 
 
 sufficiently comprehensive, and will in every way serve the purpose of the finished drawing, it is a 
 waste of labor to make the latter. On the other hand, no pains should be spared in the exe- 
 cution of the drawing if it will better express the designer's conception of the mechanism. No 
 portion of such work should be carelessly done, even in the so-called off-hand sketch, 
 or drawino-. A sketch may consist of few lines and be comparatively rude, but it must not be 
 thouo-htlessly executed. Again, the draftsman must consider the class of mechanics to whom his 
 drawing is addressed. He should anticipate their wants, and to a certain extent, guard against 
 mistakes which may arise from their ignorance. Experience alone will make a man proficient in 
 the use of this graphic language, but a knowledge of the laws governing it will greatly facilitate 
 its acquisition. 
 
 The development of machine drawing, during the last few years, has resulted in the introduc- 
 tion of many methods and technicalities which were not formerly required. The technical part of 
 architectural drawing has never necessitated such rigid conformity to laws concerning the arrange- 
 ment of views, methods of sectioning, figuring, and other details, and it is for this reason that many 
 apparent innovations have necessarily been made upon the old established systems of drawing. No 
 one chano-e has caused more discussion than the rigid adherence to the representation of all objects 
 in what is known as the third angle of projection, that is, the placing of the top view on the top of 
 the sheet, the view of the right-hand on the right-hand of the sheet, etc. ; in short, placing the 
 view nearest to the face which it represents. But this has now passed the stage when the advan- 
 tages to be derived by this method may be questioned, and to-day, no well conducted draughting 
 room will permit any other system to be used. 
 
 This treatise presupposes a knowledge of the use of instruments and the theory of orthographic 
 projection. Its aim is to teach the more concise methods of graphically expressing mechanical ideas.
 
 ]6 CLASSES OF DRAWINGS. 
 
 Classes of Drsiwiug'S. — The different types of drawing required for siiop uses are as 
 follows : 
 
 The General or Assembled Drawing. — This consists of a representation of the complete 
 machine with all of its parts sustaining their proper relations to eacli other. This drawing may 
 contain information suitable only for assembling the macliine, and illustrating tiie general design, 
 or it may also include some or all of the details of the machine. The drawing of the Tail Stock, 
 Plate 11, is of this type. 
 
 Detail Drawings. — These illustrate each piece separately, with all of the information neces- 
 sary for its construction. This type is shown by Plates 7 and 8. It is customary to devote one 
 or more sheets to forgings, and others to castings, or when the parts are few in number they may 
 be placed on a single sheet. 
 
 Bolt Drawings. — Where a great variety of bolts is used on a machine, a special drawing 
 of them is required, or a Bolt List may be prepared which shall enumerate the sizes, type and 
 number of each. 
 
 Motion Diagram. — This type would be used only in complicated machinery comprising a 
 number of mechanical motions more or less complicated. Sucli a drawing would instruct concern- 
 ing the relation of important centers, direction of motiun, relative velocity of shafts, etc. 
 
 The size of paper used for the drawing is usually determined by certain fixed standards 
 peculiar to each shop and largely dependent on the uses for which the drawings are designed. For 
 the problems of this book, the sizes of 10x14 and 14x20 inches are recommended, but nearly all 
 of the work may be drawn on the smaller size. These dimensions are for the margin line, the 
 size of the paper being as much greater as may seem suitable. From one-half to one inch margin 
 is sufficient.
 
 LAY-ODT OF THE DRAWING. 17 
 
 The Lay-out of the Drawing. — Having put down the paper and ruled the margin, obtain 
 a "lay-out" of the sheet. This consists in the making of a rude sketch of the various parts and 
 views to be put on the drawing, so that ample room shall be provided for each piece and the whole 
 be symmetrically arranged. This operation is usually neglected by students, and inevitably leads 
 to trouble and the loss of much more time than would be required for the preliminary sketch. 
 Where a number of details are to be put on a drawing, as shown on Plate 8, provision must be 
 made for the proper marking of each piece as well as the necessary figure lines. If the detail is of 
 a small piece, like some of the screws on this plate, much more space should be allowed than 
 would be sufficient for the piece itself, as the title alone may require more space than the drawing 
 of the piece. If provision for each part, and the necessary views, be not made before the drawing 
 is begun, the draftsman may discover, when it is too late to rectify the mistake, that some piece 
 has been omitted, thus requiring an entire sheet to be devoted to this piece, or the re-drawing of 
 the whole. 
 
 Nnniber and Arrangfenient of Views. — This discussion of the arrangement of a 
 sheet leads to the consideration of the number and arrangement of views. The only rule for 
 guidance in this matter is to draw as few views as shall be consistent with the interpretation of the 
 idea, but enough to accomplish this fully. In the valve drawing, Plate 3, one view would suffice 
 for the complete representation of the object, two being shown here to simplify the problem for the 
 student. In Plate 9, two views are barely sufficient for the ready reading of the drawing. 
 
 The views should bear such relation to each other as that already prescribed for the orthographic 
 projection of objects in the third angle, the top view on the top of the sheet, the view of the right 
 side of the object to the right of the sheet, etc. A good rule to observe for attaining this end is 
 to place the view nearest the face represented.
 
 18 SCALE TO BE USED. 
 
 In the making of .a general drawing which is to be used for assembling only, omit as much 
 detail as possible. 
 
 Parts which may be well represented on one view need not necessarily appear on the other 
 views. 
 
 Draw nothing that may mislead or that does not assist in conveying the idea to be expressed. 
 
 When a written note will serve the making of a second view, do not hesitate to insert it. 
 
 In general, show mechanism in its working position, with the parts sustaining their proper 
 relations to each other. Thus in drawing a valve, let it be either wide open or closed. In showing 
 a steam cylinder, draw the piston at extreme end of stroke, and the valve in its proper relation to 
 the piston. 
 
 f////////////////////////////////////W/W'fW/Wf 
 
 \\\\\\\\\\\\\\\\\W\\\^\\\\\\WvA\v\\^^^ 
 
 Scale to be Used. — The scale of a drawing is usually dependent on the size of sheet and 
 number of views. These being determined, use the largest possible scale. Those commonly em- 
 ployed are : Full size, Half size. Quarter size (3 inches=l foot), Eighth size (li inche8=l foot). 
 The scale of 2 inches =1 foot is much used in locomotive practice, but is not to be commended for 
 general use as it requires special division of the scale. 
 
 The most convenient form of scale, and indeed the only kind that the author can recommend, 
 is the flat boxwood scale with white edge, graduated alike on both edges. Such a scale, divided
 
 tENCILtNG THE DRAWING. 19 
 
 into sixteenths for its entire length, and thirty seconds for the first inch from either end, is suitahle 
 for use on the Full, Half Quarter, and Eighth size drawings. In using this form of scale for a 
 Half size drawing the reduction is easily made, since all dimensions are halved, but in the Quarter 
 size, a difficulty would be experienced if it were necessary to figure the fourth part of all dimensions 
 before laying them off. This, however, may be obviated in the following manner which is best 
 illustrated by an example. Suppose it is required to lay off 19^ inches. Remembering that one- 
 quarter of an inch of the scale represents one inch, lay off as many quarters as there are inches 
 required, and since one-thirty-second of the scale represents one-eighth of an inch, add seven of 
 these divisions to the amount already measured. In short, it is using the scale as though each 
 quarter of an inch was marked as an inch in the same manner as the regular quarter scale division. 
 The same method may also be applied to the eighth scale. But if the ordinary graduation for a 
 quarter or eighth size be desired, let it be on a scale separated from all other graduations. The 
 ordinary triangular scale with its numerous graduations and awkward shape is probably the worst 
 form of scale that was ever devised, especially when made of steel. The draftsman who has any 
 consideration for his eyes will never use a steel scale for general work. 
 
 Method of penciling the drawing. — Locate main center lines according to lay-out 
 sketch, and begin to draw the view which best illustrates the object. 
 
 Next locate leading lines and surfaces. If the subject be the head-stock of a lathe, draw the 
 spindle, fix the position of bearings and pulleys, and then proceed with the drawing of the casting. 
 If a stub-end drawing is required, as in Plate 5, lay oflTthe dimensions for the principal lines in 
 much the same order as indicated by the letters alphabetically arranged. First, the diameter and 
 length of the box A and B. Then the position of end of rod C, depth of rod G, keys and 
 key ways, intersections, etc.
 
 20 INKING. 
 
 Omit minor details until all else is finished. If a bolt, key, spring or any other such detail 
 occurs, its position may be marked, but the drawing of it should be deferred until all else is proved 
 correct. 
 
 Do not complete the views separately, but having one well begun, commence the drawing of 
 others. In this manner errors are more readily detected, the drawing of each view becoming a 
 check to the others. 
 
 Ink no part of a drawing until the penciling be complete. In a complicated drawing, students 
 are often tempted to ink a view or part of a view, which they feel confident to be correct, and 
 before quite finishing the drawing. This should never be done. 
 
 Method of Inking. — The order to be observed in the finishing of a drawing is as follows : 
 Ink all circles and circular arcs, beginning with the smallest. This includes all fillets and round- 
 ino- of edsee. If shade lines are used, shade each arc at the time of inking it. It will be observed 
 then that the width for both fine and heavy lines is determined by the shading of the first circular 
 arc. Do not use too fine a line, remembering always that the drawing must be distinct even after 
 much use and possible abuse. Next, ink all other curved lines, such as lines of intersection, etc. 
 
 Finally, ink all fine lines, both full and dotted ; and then the heavy or shade lines. 
 
 Section lines should not be drawn until the figuring is completed. 
 
 Shade Lines. — By some draftsmen the use of shade lines is condemned while others con- 
 sider a drawing as incomplete without them. Both err by adopting either system to the exclusion 
 of the other, for while shade lines may be useless on many drawings, there are others which would 
 be incomplete without them. The draftsman must decide the matter for each drawing which he 
 makes, always using them when they may assist in the reading of the drawing, but otherwise 
 omitting them.
 
 LINE SHADING. 
 
 21 
 
 The only practical direction that may be given for the method of using them is to shade the 
 right-hand and lower edges of all surfaces, remembering that in the case of contact between sur- 
 faces, the line represents the surface nearest the observer. Where the surfaces are flush, as is the 
 case between the stub-end of the connecting rod and the strap, Plate 5, the line must be fine. 
 Never shade the intersecting lines between visible surfaces of the same piece, as illustrated by the 
 division line of the faces of a bolt-head. Shade the lower right-hand quadrant of outside circles 
 and the upper left-hand quadrant of inside circles. Do not permit the shade line to encroach on 
 the surface which it bounds. 
 
 Cylindrical surfaces are sometimes illustrated by fine lines only, when shade lines are used 
 on other surfaces. This method is especially adapted to the illustration of a complex piece having 
 an insufficient number of views or lacking in detail. Plate 9 will be found to illustrate this method. 
 
 Line Sluiding.— It is often necessary to express the character of a surface more clearly 
 than would be done by the simple outline or by the use of shade lines. This is ordinarily accom- 
 plished by the use of line shading. Plate 16 illustrates the method of shading the more common 
 surfaces. In studying these methods and in applying them to the practical drawing it should be 
 observed that the best effects are frequently produced by the fewest lines, and the more we are 
 able to reduce the number of lines of all types, the better the drawing. By the system here 
 shown, much of the cylindrical and conical shading might to advantage be done by a section liner* 
 which in the case of large surfaces would insure more regular work. In shading large cylindrical 
 surfaces such as Fig. 1, Plate 16, use only fine lines for the upper portion. Increase the space 
 between the lines quite rapidly and stop at about one-half of the radius from the top. The shad- 
 ing of the lower part may be begun at a distance of about one-quarter of the radius from the center. 
 
 * For a descriptiou of this instrument and tlio method of operating it see page 24.
 
 22 LINE SHADING. 
 
 These lines may be spaced equally, although the appearance is somewhat improved by increasing 
 tiie space for the first two or three lines. The cylindrical effect is produced by increasing the 
 width of the lines until near the bottom, when they are slightly decreased in width, but this latter 
 is not necessary save in cylinders of large diameter. Fig. 4 illustrates the section of a cylinder, 
 which being a concave surface, necessitates the drawing of the darker shade lines at the top, but in 
 other respects the method of drawing is the same. 
 
 In the shading of small cylinders the effect is often improved by shading the lower side only. 
 Compare Fig. 3 with the shaft of Fig. 5. 
 
 Bell-shaped surfaces are frequently shaded as in Fig. 2, but that of Fig. .S involves no cir- 
 cular arcs and for small pieces is equally good. Fig. 8 represents a cone shaded by parallel lines 
 in a manner similar to the cylinder. The usual method of doing this, by drawing all of the shade 
 lines radiating from the vertex, is very difficult, requires more lines, and rarely looks as well. 
 
 The pipe shown in Fig. 7 illustrates the method of grading the lines so that the upper and 
 left-hand portion shall represent the illuminated parts. Had the bend been to the right, the shad- 
 ing would have been more simple. The conical portion of the pipe flange shows yet another 
 method that may often be used to advantage. The system used for the shading of the sphere. 
 Fig. 6, will be apparent from the illustration. 
 
 It is rarely necessary to shade plane surfaces and should be avoided when possible. When neces- 
 sary to emphasize the fact that a plane is inclined to that of the paper, the method of Fig. 9 may 
 be used. 
 
 Fig. 27 illustrates a method representing knurled surfaces. The angle of the cross lines must 
 be varied to conform to the ratio of diameter to length of surface, for it will be observed that no 
 change is made in the spacing until a series of lines has been drawn from A to B. The spacing 
 in the cut is slightly exaggerated to better illustrate the method.
 
 THE TITLE. 
 
 23 
 
 The Title. — The title of a drawing should always be placed in the lower right-hand corner 
 of the sheet, and should designate, first, the name of the mechanism ; second, the name of the 
 special detail ; third, the scale ; fourth, the date, which is always that of the finishing of the draw- 
 ing. The draftsman's name or initials should be printed in the extreme 
 corner. Besides this, such data as the " time number," the number of B 
 drawings belonging to this special machine, and other data may be given ; 
 but the information essential to every drawing is that given above. 
 
 The student must decide for himself concerning the character of 
 type to be used. Several styles are illustrated in the plates. That most 
 easily acquired is shown in Plate 9, but it is not so clear as those of 
 Plates 3 and 7. Plate 10 illustrates a most excellent style but rather 
 difficult to execute well. The round writing of Plate 11 is much used, 
 but it comprises many objectionable forms of letters, and the figures are 
 too indistinct to be used on the dimension lines. Whatever style is 
 adopted should be adhered to until it can be rapidly written, and always 
 without mechanical aid. 
 
 In the final cleaning of the sheet it should be borne in mind that 
 many of the auxiliary lines used as construction lines may be useful to 
 the pattern maker, or possibly to the draftsman, at some later day. Thus 
 
 Fic. 27 
 
 It IS often well to 
 leave some of these lines on the drawing even though it may present a less neat appearance.
 
 CHAPTER III. 
 Sectional Views. 
 
 Use of a Section. — For tlie complete representation of mechanism it is frequently nec- 
 essary to make use of a section in order that some details which would otherwise be hidden may 
 be shown in full. The sectional view is a representation of the object after it has been cut by an 
 imaginary plane. When possible, such a view should be used instead of introducing numerous 
 dotted lines, as the latter tend to produce confusion. There are several conventional methods of 
 representing the surface of an object when cut by a plane. That most commonly used, and for 
 most purposes the best, consists of parallel lines usually drawn at an angle of 45° across the cut 
 surface. By changing the direction of these lines a clear distinction may be produced between 
 the parts of different pieces which may be in contact, and by varying the character of the lines, a 
 difference in material may be indicated. Plate 1 1 is an excellent example of the use of a section. 
 
 Section Liners. — The regulating of the space between these lines is frequently done by 
 the eye, but it may be more easily and rapidly accomplished by the use of a section liner. This 
 is an instrument by means of which the triangle is made to move through equal spaces fixed by a 
 gauge determined by the draftsman, and thus avoiding the care and time usually required for the 
 performing of this operation by the eye. Unfortunately, however, most of the section liners to be
 
 NOTATION FOR SECTION LINING. 
 
 25 
 
 found are complicated and unsuitable for the purpose. No more simple or effective tool has been 
 
 designed for this use than that shown by Fig. 28, which 
 
 consists of a strip of wood not over an eighth of an inch 
 
 thick, having parallel edges and provided with a stop on 
 
 either end, one of which is adjustable. The only care 
 
 necessary to be observed is in keeping the edges of the 
 
 triangle and slide together, but if the edge of the latter 
 
 is placed against the blade of a T square, this difficulty 
 
 is partially overcome. The method of operating, which 
 
 scarcely requires explanation, is as follows: — Having 
 
 drawn a line by the triangle, in the position shown, by 
 
 means of the second finger push the triangle against stop 
 
 B while holding the slide firm with the first finger. Next, 
 
 while holding the triangle fast, move the slide until stop A touches the triangle and draw the 
 
 second line. Of course practice is required to manipulate the two pieces with ease and rapidity, 
 
 but the saving of the otherwise necessary strain to the eyes compensates for this. 
 
 Notation for Section Lining.— Plate 15 illustrates the various types of sections avail- 
 able for the representation of ditferent materials. Save in the case of cast-iron (Fig. 1) there is 
 no general agreement among draftsmen as to the material which each type of lining shall desig- 
 nate. Such a standard was proposed to the American Society of Mechanical Engineers,* but 
 fortunately failed of adoption. It would only have added one more complication to the intrica- 
 
 FlC. 28 
 
 ♦Transactions of the A. S. of M. E., Vol. IX, page 107.
 
 26 
 
 NOTATION FOR SECTION LINING. 
 
 cies ot modern niacliine drawing, and made a misunderstanding possible. If the slightest doubt 
 as to the nature of the material represented is likely to occur, write the name of the material on 
 the section. No type of sectioning should be used that involves the making of two widths of lines. 
 Dotted lines should be used sparingly and types shown by figures 4 and 10 are still less 
 desirable. 
 
 In the illustrations of this book the following no- 
 tation has been used for section lines. Fig. 1 repre- 
 sents cast-iron. Fig. 2, wrought-iron and steel. 
 Fig. 3, brass, bronze, etc. Fig. 4, Babbitt's metal 
 or other lining metals. Fig. 6, brick. Fig. 7, wood, 
 across and with the grain. Fig. 8, stone. Fig. 9 
 
 is used to section a surface which is invisible. Fig.'s 
 b and 10 are undesignated. The former is often used 
 to produce a sharp contrast with other sections, and 
 fref|uently employed on Patent Office work, and for 
 illustrations where figures and figure lines are omitted. 
 Of course many other types may be devised, but 
 it rarely occurs that the variety here represented 
 will not suffice. Care should be exercised in choos- 
 ing the spacing for section lines that tiiey be not too fine. No rule can be given for the distance, 
 which woidd he almost entirely dependent on the size of the section represented. 
 
 Dotted Sections. — In some c.Tses it is necessary to represent a piece of mechanism by a 
 full or external view, when a section is also required to explain some little details of it. Instead 
 
 Fic. 29
 
 COLORED SECTIONS. 
 
 27 
 
 of making a separate sectional view it may often suffice to dot tlie obscure section, either by the 
 method shown in Fig. 29, one-half of which shows the section by dotted lines, while the other 
 
 
 ^ V'.VVqVI'-'. 
 
 
 Fig. 30 
 
 half represents the section by a dotted outline only ; or by that of Fig. 30 in which the dotted 
 outline is emphasized by a series of dashes. This second method may be employed to advantage 
 when penciling a somewhat complicated drawing which may or may not be shown in section
 
 28 COLORED SECTIONS. 
 
 when inked. Thus in the case of Plate 11, illustrating the Tail Stock of a lathe, the lines of the 
 penciled drawing would be much confused if section lines are omitted until the inking is done. 
 But the section lines should never be drawn in pencil, as it makes the inking more difficult, 
 besides necessitating the erasing of pencil lines among inked section lines. If, however, the 
 section be indicated, as in Fig. 30, the drawing may be made very distinct, and the penciled 
 lines or dashes be drawn so fine as to require no erasing. 
 
 Colored Sections.— It is unfortunate that reproductive processes, such as blue-printing, 
 make the use of color for sectioning impracticable. It is in every respect the best method of repre- 
 senting them, for by varying the shade, adjoining pieces of like material may be clearly shown, 
 and by changing the color, the character of the metal may be expressed. The time required to 
 perform the work is also much lessened. Where the system of tracing a drawing is still employed, 
 this method may be used instead of section lining, as is already done in many locomotive works 
 where the tracing, instead of the drawing, is placed on file. The practice of sending to the shop 
 a drawing, instead of a tracing or blue print, is one to be commended, as the best copy is then 
 placed in the hands of the man who finds the most difficulty in reading a drawing. 
 
 When colored inks are used for section lining, the metal may be designated by the color of 
 the line instead of by the character of the section line. Black is always used for cast-iron ; Prus- 
 sian blue for wrought-iron and steel; yellow ochre, or Indian yellow, for brass, (a very little 
 carmine added to the yellows will give more body to them), burnt sienna and burnt umber for 
 wood, and sometimes for leather. 
 
 Choice of Cutting Planes.— In representing an object in section, choose such a position 
 for the cutting plane that all of the details requiring to be shown shall be seen in the clearest 
 manner.
 
 CUTTING PLANES. 
 
 29 
 
 t*ortions of the object lying berjond the cutting plane 
 need not be shoivn on the sectional view unless it may be 
 tliought desirable. In Fig. 33 the flange bolts lying beyond 
 the plane are not shown, since it would only add to the labor 
 of drawing and produce confusion as well. 
 
 l^ke pla7ie of the section need not be continuous. The 
 sectional view of the Tail Stock, Plate 11, includes a section 
 made by two planes, but no confusion need arise from this, 
 and in actual practice the note concerning the plane on which 
 the section is made might be omitted. 
 
 All that lies within the cutting plane need not be sec- 
 tioned. 
 
 Fig. 31 illustrates a cylindrical piece with hub, ears, and 
 ribs. Two sectional views are shown, the lower figure repre- 
 senting the object as cut by the plane A B, the section passing | 
 through one rib, the central hub, and one ear. The other 
 section is the conventional representation of the surface cut by 
 the same plane. In this case the ear, rib, and central hub are 
 omitted from the section, but shown as though they were imme- 
 diately behind it. A good illustration of this case is also seen 
 in Fig. 32 which illustrates the conventional method of drawing 
 gears, hand wheels, pulleys, etc. Here the plane A B passes 
 through a tooth and arm, but the sectional view shows both in 
 
 FIG. 31
 
 /VrYfV^ 
 
 'mm^ 
 
 ^?^w^ 
 
 Fic.32
 
 CUTTING PLANES. 
 
 31 
 
 full. The key and shaft are also drawn in full, although 
 lying in the cutting plane. In general do not section 
 such details as a shaft, a key, a bolt, a gear tooth, or 
 the arm of a wheel. 
 
 A. section of a syinmelrical jjiece .s/ioulJ be sug- 
 gestive of symmetry. In the correct sectional view 
 of Fig. 32, both ears and ribs are shown as though 
 they were two, four, or six, instead of three, but a 
 note signifying the number of each is a sufficient expla- 
 nation. Again, in the case of the stuffing-box gland, 
 Fig. 33, the ears are better shown in full, if they are 
 small in comparison with the diameter of the gland. 
 The discretion of the draftsman must be used in show- 
 ing of the flange bolts since they may be drawn in full, 
 or dotted as in the figure ; but in either case their true 
 relation to the cylinder should be shown. To project 
 the bolt, shown at the left-hand, from its position as 
 drawn in the top view, would add nothing to the infor- 
 mation required, but rather tend to mislead. 
 
 In the illustration of the Rear Bearing for the 
 Screw Polishing machine, Plate 8, an exception was 
 made to this principle by reason of the confusion which 
 would otherwise have been produced by the section 
 
 Fig. 33
 
 32 
 
 BROICEN SECTIONS. 
 
 lines being drawn across the slotted space for leather. In actual practice, the piece would be sec- 
 tioned so as to appear symmetrical. 
 
 Broken Sections. — When a portion of a rod, bar, pipe, or other symmetrical piece is shown 
 as broken, the section should be suggestive of the shape. Fig. 34 represents a cylindrical rod. 
 Fig. 35, a bar of rectangular section. Fig. 36, a pipe. Fig. 37, a rod of wood. The outlines 
 of these sections may be drawn with an ordinary pen, but the lines should not be jagged save in 
 the representation of wood, as in Fig. 37. 
 
 Fic. 36 
 
 Fic 
 
 It is quite common to show the section made by a plane at right angles to a view, upon the 
 view itself. The sections of the gear arm. Fig. 32, made by the planes E F and G H illus- 
 trate this. 
 
 Figuring. 
 
 After the inking of a drawing is completed, and before the section lines are drawn, the figure 
 lines are required to be put on. This is the most important part of the making of a drawing, and 
 requires the greatest care and most experience. Unfortunately, at this stage the student, and not 
 unfrequently the draftsman, becomes wearied with his work, and the subsequent operations are too 
 often hurriedly and carelessly performed. While it may frequently be necessary to make haste in
 
 tiGUBlNG. 33 
 
 the figuring of a drawing, it must never be hurriedly done and the most scrupulous care should be 
 exercised in the drawing of every dimension line, and the making and checking of every figure. 
 
 As an illustration of the method to be employed in the figuring of a drawing, consider the 
 case of the stub-end, Plate 5. Suppose the drawing be in readiness to figure. We have first to 
 consider the class of mechanics for whom this drawing may be made. In general, the needs of the 
 pattern-maker are first to be thought of; but inasmuch as a pattern serves for many duplicate 
 pieces, the dimensions of unfinished parts may usually be omitted. In such cases the draftsman 
 will furnish the pattern-maker with a sketch or tracing having the necessary figures. This will 
 save the crowding of the drawing with figures which when once used are not likely to be required 
 attain. If the drawing is to be sent to a distance where detailed information may not be readily 
 obtained from the draftsman, these figures must not be omitted from tiie drawing. 
 
 The requirements of the forge shop are usually met by sketches specially prepared for that 
 department, but the figures given for the machinist will ordinarily suffice for the smith. In giving 
 dimensions for either pattern-maker or smith, specify finished sizes only, leaving the amount of shrink 
 or finish required, to his judgment. In the case cited, figures for the machinist only have been given. 
 
 It is customary to draw the figure lines in blue ink and the center lines in carmine, but this 
 order may be reversed, or one color used for both. If colors are used for these lines they are bet- 
 ter drawn full. Begin by drawing the dimension lines necessary for locating the center lines and 
 working faces. In the connecting rod the diameter and length of the pin, or box for same, is the 
 first consideration. Next locate end of rod C, after which completely figure that part by dimen- 
 sion lines marked D, E, F, G, H, I, J, K, L. Then consider the gib and key O, P, R, S, etc. 
 Next, the set-screw and strap, and finally, figure the boxes, if figures given for other parts do not 
 already include these.
 
 Si FIGURING. 
 
 The dimension lines being completed, the center lines should next be drawn, after which the 
 witness marks (or arrow points) and figures, are to be made. The drawing should then be cleaned 
 and finally section lined. 
 
 In figuring detailed drawings like Plates 7 and 8, great care is necessary to avoid mistakes, and 
 the draftsman will always do well to examine carefully the figures on all parts that fit together. 
 Thus the diameter and length of the bearings must accord with the dimensions for the spindle fitting 
 the same. 
 
 The dimensions on a drawing should always indicate the full size, and are independent of the 
 scale to which the drawing may be made. In connection with this it is well to note that the scale 
 dimensions of a drawing should never be spoken of, as great confusion would arise from it. To 
 illustrate : let us suppose a shaft eight inches in diameter to be drawn one-quarter size. It would 
 then measure two inches, but should never be spoken or thought of as other than eight inches, the 
 real diameter ; and if the draftsman was asked to add an inch to the diameter it is his business to 
 see that the proper increase is made according to the scale which he may be using. In this case 
 he would have to add one quarter of an inch to the diameter as drawn, but it must always be 
 spoken of as one inch. 
 
 Rules to be Observed in Figuring Drawings. 
 
 1. Dimension and witness lines should be made in blue ink, centre lines in carmine, arrow 
 points and figures in black. 
 
 2. Dimension lines may be continuous or broken, as •* >■ ■< *■ 
 
 The latter form is of advantage only in indicating the position to be occupied by the figure.
 
 S-IGURING. 
 
 35 
 
 3. Centre lines should never be used as dimension lines. 
 
 4. Dimension lines should not be too close to line of the object. 
 
 5. Make arrow point or witness point thus ■< and never < 
 
 6. Make the arrow points exactly touch the lines to which the dimensions are given. 
 
 7. Give dimensions overall, as well as sub-dimensions. 
 
 8. Exercise great care in the making of figures, adopting some plain type, and as far as 
 possible, using one size. 
 
 9. Separate the numerator and denominator of a fraction by a horizontal line thus, (|) never 
 using an inclined line for this purpose. (The horizontal line may be omitted, by writing the 
 figures above and below the dimension line, as < — • 1 >). 
 
 10. Write the figures in line with the dimension line, and never inclined or perpendicular 
 to it. 
 
 11. Figures should face bottom and right side of drawing. 
 
 12. If all dimensions are in inches, the inch mark ' need not be used, but when feet and 
 inches are to be represented, write as follows, 3 Ft. 6", or if the foot mark ' is used the figures 
 should be separated thus, 3'— ^6'. 
 
 13. AVhen using large and small dimensions on the same drawing it is well to express all 
 dimensions less than three feet in inches, and larger ones in feet and inches, thus 29' 3'^— 
 
 3 5". 
 
 14. First figure that view which illustrates most completely the details of the object. 
 
 15. In general, do not repeat figures. 
 
 16. Figure to centre lines and faced surfaces. 
 
 17. Figure diameter of circle, in preference to radius, and draw the line at an angle.
 
 36 FINDING DIMENSIONS. 
 
 18. If the radius be used instead of diameter, locate clearly, as, -<^—^" ^•*-^' 
 
 19. Do not draw section lines across the figures. 
 
 20. In correcting a figure without altering the drawing, affix the word " make," which in- 
 dicates a knowledge on the part of the draftsman of the existing discrepancy in the drawing. 
 
 Finding' Dimensions. — The figure for a special part may be more readily found by first 
 looking for the arrow point toucliing one of the lines limiting this part. If the point is not to be 
 found on one view, seek for it on other views, and, failing to find it, the figure may be declared 
 missing. To illustrate, sui^pose the combined widtli of gib and key of the connecting rod, Plate 
 5, is required. Beginning at the top of the key we find tiie first arrow [Joint leads to the dimen- 
 sion W, the second to the dimension E, the third to the required dimension O. This method 
 will greatly facilitate the finding of figures on complicated drawings, and enable the workman to 
 determine quickly whether the figure be missing. 
 
 Method of indicating' surfaces vvliicli are to be ftni,slied. — Although 
 this does not properly come under the head of the suliject of figuring, yet it often has to be con- 
 sidered at the same time. On many drawings in all shops it is unnecessary to give this informa- 
 tion, and in many shops it is never given. But where drawings are elaborately detailed and the 
 work of construction much subdivided, it is often necessary to iildicate this on the drawing. It 
 may be done by writing the word " finish," or simply the letter " f " across the line representing 
 the surface to be finished. Or a colored ink may be used to draw a line parallel with the surface 
 to be finished. This latter method is objectionably from the confusion caused by the increased 
 number of lines, but may be used to advantage on blue prints by using carmine and soda water 
 for the ink. This distinguishes the finish line from all others.
 
 technical sketching. 37 
 
 Technical Sketching. 
 
 The ability to make a free-hand technical sketch of a piece of mechanism is of more impor- 
 tance to most mechanics than that of making the ordinary mechanical drawing with instruments. 
 Unfortunately, however, it requires much more skill to do this, not because of the practice required 
 for the clever handling of the pencil, but by reason of the difficulty in executing a drawing without 
 the mechanical checks to errors of judgment in the representation ; and also because of the neces- 
 sity of a more concise expression of the idea than would be given in the drawing. Moreover, a 
 thorough knowledge of projection and the principles of machine drawing are as requisite to 
 technical sketching as to technical drawing. The enumeration of these difficulties is not for the 
 purpose of discouraging the student, but rather to direct his energies toward gaining a mastery of 
 the most efficient method of technical expression. 
 
 One of the most important functions of the sketch is in the development of a design. At 
 such a time the engineer cannot resort to the more laborious process of instrumental drawing, but 
 must rapidly express his thoughts by free-hand sketches. Some of these preliminary sketches 
 may be as complete in the important details as the more elaborate drawing which the draftsman 
 must finally make for the shop use. 
 
 Practice in acquiring this invaluable art of rapidly and clearly expressing one's technical ideas 
 may be acquired in several ways. Tiiat most to be commended is the practice of sketching 
 directly from the object according to the method hereinafter explained. A perspective or isometric 
 representation is often useful as a substitute 'for many views, or to more sharply define certain 
 obscure details, but if the student is unfamiliar with these methods, the orthographic representation 
 will suffice for all cases..
 
 38 TECHNICAL SKETCHING. 
 
 When it is not possible to obtain models from which to work, a good exercise will be found 
 in a free-hand detailing of the parts of a finished drawing, after which the sketch may be tested by 
 making the assembled drawing from it. 
 
 A most valuable training, both in sketching and in observation, may also be had from 
 memory sketches. For this purpose choose some simple model or the drawing of a plain object, 
 and, having carefully studied it, set it aside and make a free-hand drawing comprising two or 
 three views. 
 
 In the making of all sketches, establish first the center lines and important details as would 
 be done in the making of a drawing, and in general, proceed in a similar manner. 
 
 Order to be observed iu the making- of a .sketch from mechanism already 
 constructed. — First : Having separated the different parts of the machine, sketch each in detail, 
 omitting nothing necessary to its complete representation. Use written notes whenever they may 
 save the time of drawing. Complete the sketches of every part before putting on any dimension 
 lines. 
 
 Second : Sketch all the necessary dimension lines with the arrow points, but do not figure 
 the sketch. Tiiere are reasons for doing this. It insures a more thorough figuring of the draw- 
 ing, as one is not diverted from the consideration of the dimensions wanted, by the measuring of 
 the pieces and writing of the figures ; it is productive of neater work, since one is not required to 
 handle the pieces which are likely to be coated with oil or covered by dust ; it enables the work to 
 be more rapidly and easily done, since it may be executed at the desk, without reference to the 
 pieces save through the sketch. This will also involve a critical reading of the sketch, and serves 
 as a check to errors of drawing. 
 
 Third ; Obtain the figures for the dimension lines indicated on the sketch.
 
 PRACTICAL SUGGESTIONS. 39 
 
 Practical Suggestions.— The sketch and its dimensions should accurately represent the 
 object illustrated. It does not follow, however, that the drawing subsequently made from this 
 sketch shall be a duplicate representation of the pieces sketched. Drawings made from existing 
 mechanisms are intended to reproduce that which the machine was designed to be, rather than to 
 copy the piece already constructed. If an attempt be made to suggest these alterations on the 
 sketch, confusion is very likely to arise. It frequently happens that the dimension of a piece may 
 be found to involve sixteenths or thirty-seconds of an inch when integers or halves or quarters 
 would serve as well : thus, if the diameter of a flange was found to measure 12^L inches, it would 
 ordinarily be inferred that 12 inches was meant, although the former dimension should appear on 
 the sketch. 
 
 Use one view if possible, and do not overcrowd the sketch with details. 
 
 Exercise such care in the making of the sketch as shall enable it to be readily used by any 
 one familiar with the technique of drawing. The character of a sketch too frequently implies the 
 supposition that it is intended solely for the draftsman who made it, and not unfrequently many 
 details are omitted to be supplied by the memory. For the information which it is intended to 
 convey, the sketch should be as complete as a drawing. 
 
 When practicable, it is well to sketch those parts which may be mechanically related so that 
 reference may be readily made from one to the other. 
 
 Sketch objects in their proper position, for it is better thus to suggest the true relation of the 
 lines and surfaces, although the dimensions alone are to be relied on to determine them. 
 
 The center lines should always be drawn with care, and the position of dimension lines 
 determined as in the case of a drawing, save that in the latter case more will be required. Figure 
 each piece independent of others. Thus, in the case of a shaft and its bearings, the diameter will 
 appear on each.
 
 40 1'ractical suggestions. 
 
 Every draftsman sliould acquire tlie habit of preserving his sketches, especially those made in 
 connection with the design of a machine, for it not unfrequently happens that an apparently value- 
 less sketch which has been destroyed becomes necessary to the complete development of a detail, 
 or invaluable as a matter of record. Two kinds of sketch books have become a part of the para- 
 phernalia of the modern drafting room ; one in which is made or filed sketclies suggestive of various 
 designs and alterations in machinery ; the other, a copy book in which may be preserved a copy 
 of every sketch sent from the drafting room.
 
 CHAPTER IV. 
 Examples for Practice. 
 
 Problem 1, Plate 1.— Assembled drawing of a Locomotive Parallel Rod. The planning 
 of this sheet is so simple as to require no sketch ; but since the principles involved do not differ 
 from those of the " lay-out "of the most complicated drawing, it is expedient that the student 
 should perform this work. The size of the sheet witliin the margin line shall be 10x14 inches. 
 Two views are required and are best arranged as shown in the " lay out " sketch. The scale of 
 the drawing will be determined by the dimensions marked D, E and F, the sum of which when 
 drawn cannot be greater than 10 inclies, and should be considerably less to allow for the title, 
 which will require from 1 J to 2 inches. The sum of tlie dimensions D, E and F according to the 
 sketch is 12 inches, which prevents the use of a full size scale but makes the half-size possible, as 
 it would require but 6 inches, leaving 4 inches for title, space between the views, and space at 
 top. Having determined H, K and L, so as to enable the drawing to present the most symme- 
 trical appearance, the center lines may be drawn. It should previously have been observed that 
 the length of the parallel rod is such as to preclude the possibility of drawing it even at half or 
 quarter scale without illustrating the bar as broken, which may of course be done, leaving suf- 
 ficient space on either end. The only section requiring to be shown is that of the rod, which may 
 be drawn as suggested by the sketch. The practice to be derived from the use of shade lines on 
 this drawing should not be neglected. For the purposes of study it is well to draw the dimen-
 
 42 EXAMPLES FOU PRACTICE. 
 
 sion lines in pencil, so that they may be well considered and changed if necessary, but in prac- 
 tice they should be drawn in ink at first. Figure the drawing so that the dimension of every de- 
 tail may be obtained. 
 
 Problem 3, Plate 3. — Assembled drawing of a Boiler Check Valve. This is to be shown 
 complete with the valve on its seat, the cap screwed down, and the coupling nut partly on. One 
 view is quite sufficient for illustrating every detail, but it is desirable to draw a side view to obtain 
 the practice. The principal view should be sectioned and the character of the metal designated 
 by the character, or color, of the section line. 
 
 Problem 3, Plate 3. — Detailed Drawing for a 2 inch Globe Valve. All of the parts are 
 to be shown separately, in like manner to those of Plates 7 and 8, but on one sheet. The lay-out 
 of this sheet will require a careful study, involving the consideration of the number and character 
 of the views. Because two views of any of the parts are shown on the plate, it does not follow 
 that the details should be similarly treated. 
 
 A more difficult but most excellent treatment of this problem would be the making of a free- 
 hand detailed sketch of the valve, figuring the same completely. Then, putting aside the plate, 
 make the assembled drawing from these sketches. Either of these methods will require much 
 more time than may at first appear necessary, but to faithfully and accurately produce one such 
 drawing is worth a dozen thoughtlessly executed. 
 
 Problem 4, Plates 4, 5 ami 6. — The drawing of a connecting-rod involves an excellent 
 problem in the intersection of surfaces, and this should be thoroughly mastered before proceeding 
 with the drawing of the rod. As the principles involved are applicable to many practical prob- 
 lems it is desirable that the student should make a careful study of each of the cases shown. 
 
 Fig". 2, Plate -4, represents a cylinder terminating in a bell-shaped end, and because the
 
 EXAMPLES FOR PRACTICE. 43 
 
 surface may be generated by the motion of a line about an axis, it is known as a surface of revo- 
 lution. The end view of this surface is shown as cut by four planes, A B, C D, A C, B D, parallel to 
 the axis, and tlie appearance of the object after having been cut is shown by Fig". 1, The prob- 
 lem consists of finding the curve of intersection E F G, together with a similar curve on the upper 
 surface which would be shown on another view. 
 
 Fig". 3 illustrates the same case without the line shading. Three views of the cylinder with 
 its bell-shaped end are shown, but they ai-e represented as cut by the planes A^ B" and B^ D**, 
 producing the intersecting curves B'' G'' D'' and A^ H'^ B' wiiich it is required to find. Since the 
 points A^, B* and D^ lie on the surface of the cylinder and at its intersection with the bell-shaped 
 end, their projection on the other views must be at the points marked by the corresponding letters 
 in these views. The limiting points H and G of the curve of intersection are readily determined 
 by extending the lines B"' C and B^ C^ until they cut the curve at the points H' and G^. The 
 top view of the point H'' must lie between A^ and B^ and directly over H''. Similarly project G^ on 
 to the front view at G''. It remuins only to determine the intermediate points in the curves. 
 Pass any plane, K L, perpendicular to the axis ; this will intersect the curved surface in a circle 
 shown on the side view by O^ P^ M' N* ; but this circle would be intersected by the plane A* B' 
 and B^ D^ at the points O^ P' M^ and N^, and hence these points will be points common to the 
 two surfaces, and therefore points of the curve of intersection. Projecting these points on to 
 the front and top views will have determined two points in each curve. In like manner obtain 
 other points. 
 
 The following practical application differs from the preceding only in that the curve of the bell- 
 shaped piece is not located. Fig. 4 illustrates this case and is the same stub-end as that shown 
 in Plate 5. In the sketch we shall have those dimensions given which are indicated by the figure
 
 44 EXAMPLES FOR PRACTICE. 
 
 lines of Fig. 4, but it will be seen that neither of the points H" or G^ are given and the position of 
 the center X is unknown. As the curve of the bell-shaped piece is tangent to the neck of the rod, 
 the diameter of which is given, it is only necessary to obtain one point in this curve to fix its posi- 
 tion. This is to be determined by revolving the point B'' until it lies in the plane of the paper. 
 To do this an end view will be required, but since economy in the use of lines is advisable, let 
 the line B'' V represent the center line of this end view, and the rectangle B'' W Y V, the half 
 end view of the stub-end. As W is the end view of the point B'' we may obtain its extreme dis- 
 tance from the axis which may be laid off on the front view at R, thus determining the revolved 
 position of B'' and the required point in the curve. Through this point and tangent to the neck 
 of the rod, with the given radius, describe the arcs representing the bell-shaped portion, observing 
 that all of the centers must be in the same line X X. These arcs will determine the limiting points 
 of the curves of intersection, and intermediate points may be found as in the preceding problem 
 and as illustrated in this figure. 
 
 The method of penciling one view directly over anotiier is commonly used when the view is 
 to serve no other purpose than that of determining lines of intersection. 
 
 Fig'. 5 illustrates a case in which the cutting plane is tangent to the diameter of the cylinder. 
 Determine the curve from the dimensions given, using the side view only for the purpose of ob- 
 taining the curve of intersection and in the manner illustrated in tiie preceding problem. 
 
 The action of a gib ami liey to produce motion of the strap for taking up the wear in 
 the boxes is illustrated by Fig. .38. A represents the stub-end, B and C the boxes, D the strap, 
 E the key, and F the gib. The parts are shown in such relative position as would exist in a 
 newly fitted connecting rod. The box, B, bears against the end of the rod, A, and is immovable, 
 all of the motion due to the wear of the boxes being made by C. In order to move the box C,
 
 EXAMPLES FOK PRACTICE. 
 
 45 
 
 toward B, the strap D must be made to move to the right. This is accomplished by driving 
 down the taper iiey, E, so as to increase the distance between the parallel faces of gib and key, 
 and since there can be no motion to the left, the gib is moved to the right, and with it the strap 
 against which it bears. 
 
 Fic. 38 
 
 The Assembled Drawing ot a Coimectiug Rod, the sketches for which are given 
 on Plate 6. This drawing will be made similar to that of Plate 5. As this is designed to be
 
 46 
 
 EXAMPLES FOR PRACTICE. 
 
 drawn on a 10x14 inch slieet, it is evident that a full representation is impossible, but the lay-out 
 sketch will enable the scale to be determined. In obtaining the curve of intersection on the rod» 
 do not draw a special end view but use the method of Fig. 4, Plate 4. 
 
 Problem 5, Plate 9. — Detail of casting of the base for a Back Rest. Two views of a 
 
 Fic. 39 
 
 back rest for a milling machine are given, to draw the details of the base, illustrating it by three 
 views. The representation given in the plate was chosen to show the use of a dotted section and 
 the advantages to be derived from the omission of shade lines on cylindrical surfaces. Without 
 the use of these systems it would be very difficult to show ail of the details by two views. The 
 only detail omitted is that of the clearance curve cut from the base for the adjusting nut. In the 
 front view this nut is shown in full section, save where it is concealed by the casting. The 
 dotted section of the side view is that made by a plane through the center of the slide.
 
 EXAMPLES FOR PRACTICE. 4T 
 
 Of course it would be desirable to detail all of the parts of the back rest as well as 
 the one specified. 
 
 Problem G, Plates 7 and 8, (see also Fig. 39). The Assembled Drawing of a Screw 
 Polishing Machine. One view only is required for the drawing of this machine, and it may be 
 drawn on a 10x14 inch sheet. Nearly all of tlie parts will have to be shown in section and some 
 of the minor details of the parts will have to be explained by notes, such as the slots in the Bearing 
 Nuts, Plate 7. The details for a leather washer and the oil feeder are shown in Fig. 39. Observe 
 that the spring here shown is that detailed on Plate 8, but must be shown as compressed when 
 drawn in its proper relation to the other parts. After having determined tiie lay-out, begin the 
 drawing by locating the center line, and position of bearings with relation to the casting, as given 
 in Fig. 39. Then, without completing any of the details, determine the position of pulleys, collar, 
 tail screw, etc. Be sure that proper provision has been made for taking up the wear of the boxes. 
 In order to avoid confusion it may be found desirable to indicate the different pieces by sectioning 
 them in pencil as directed on page 27. 
 
 A good method of illustrating the degree of a taper is shown on the detail of the bearings, 
 Plate 8. This signifies an increase in the radius of one-tenth of an inch for every inch of length. 
 If the taper is designated by figures without the lines, it is always questionable whether the in- 
 crease is in the diameter or the radius. In practice, the taper would usually be designated by a 
 number having reference to some standard used by the shop. 
 
 Problem 1, Plate 10.— Detail of a Crosshead. The type here shown differs from the ordi- 
 nary form of crosshead in being made in halves, the parts being united by four #)oIt8 which also 
 serve to clamp the piston-rod to the crosshead, and to prevent any movement of the slide-gibs, 
 other than tliat governed by tiie gib-screws. Three views of one-half of tlie crosshead will be
 
 48 EXAMPLES FOR PRACTICE. 
 
 required, the only difference between the halves being in the diameter of the hole for the crosshead- 
 pin, and the key for the same. A note will suffice to ex[)lain this difference and if thought desir- 
 able, one of these holes may be shown in red. Two views of the slide-gib will be sufficient. The 
 pin and screws are also to be detailed. The scale and the size, number and arrangement of the 
 sheets are left to the discretion of the student. 
 
 Problem 8, Plate 11.— Details for the Head Stock of a 17 Inch Lathe. The section 
 lines clearly indicate the character of the metals used, and the drawing and figuring is 
 sufficiently complete to enable all of the forms and dimensions to be determined. The value of a 
 carefully made lay-out sketch will be more apparent in connection with this problem than that of 
 any preceding one. Draw three views of each of the [larts [upper and lower], of the main cast- 
 ing. See that all parts are completely and correctly represented and figured, that the number of 
 each piece and the cliaracter of the metal be specified, and finally, make sure of the accuracy of 
 all by a careful examination of every detail and the checking of the figures. 
 
 If the student is not already familiar with a lathe, he should inform himself concerning its 
 construction, design and management, by such means as he may have at his command. That 
 most to be desired would be the knowledge gained directly from the working machine by that most 
 valuable of all educational methods, observation. 
 
 Problem 9, Plates 13, 13 ami 14. (Also see Fig. 40.) Assembled Drawing of 
 the Head Stock of a 16 Inch Lathe. — The representation required is that shown in Fig. 40, 
 save that it must be more complete, involving the use of much sectioning. It must be figured 
 for machinists o«ly, therefore no figures for finished parts must be omitted. It would be well to 
 draw this full-size although that would necessitate a very large sheet, and the possible separation 
 of the front and side views, each requiring a sheet. The sketches have been drawn to no scale,
 
 EXAMPLES FOR PRACTICE. 
 
 49 
 
 although the proportion of the various parts have been preserved where practicable. Small parts 
 have necessarily been enlarged in order to make the drawing legible. Plate 12 includes the main 
 casting together with the boxes and caps. The cone and coneheads are also here shown. Plate 
 
 FiC. 40 
 
 13 illustrates small castings and brass details with a few accompanying forgings. Plate 14 is 
 devoted to forgings and gears. By reference to Fig. 40, it will be observed that in the main 
 view, the upper shaft, called the quill, is a revolved position of that shaft, the center of wliich is 
 shown on the side view at A. If an attempt had been made to draw this in its proper position
 
 50 EXAMPLES FOK PRACTICE. 
 
 beliind the main casting, it would have resulted in confusion, and would have required another 
 view to illustrate the simple details shown in the figure. This method of illustrating a train of 
 o-ears as though their shafts were all in one plane is an excellent device for detailing a system of 
 ^earino-, showing the gears, shafts, distance between centers and the actual or relative velocity 
 of the several shafts. In connection with this, an end view should be shown with the centers of 
 the shafts in their relative positions and the pitch lines of the gears also drawn. AVhen such a 
 representation is made of several trains of mechanism operated by a single driving shaft, but per- 
 forming different functions, the pitch lines of the different trains may to advantage be represented 
 in different colors. Referring again to Fig. 40, it will be seen that the gears shown in the front 
 view are shown in working contact, the distance between their centers C being equal to one- 
 half the sum of their pitch diameters. But in the side view, these same gears are not drawn in 
 contact but in their extreme position to the left. This lateral movement of the back-gear is 
 accomplished by means of an eccentric quill shaft, as may be seen by Plate 14. The intermediate 
 o-ears E F are for changing the direction of the motion transmitted through the change gear 
 marked K, to the screw operating the carriage of the lathe, but not shown in the figure. The 
 centers B E and H do not lie in the same plane, and since it would be desirable to represent them 
 in the same sectional plane, when drawing the front view, it will be necessary to draw the shaft, 
 havino- its center at H at a different hight in the front view which would be rather objectionable, 
 or to so change tlie diameters of gears E and H that the gear E could be shown in the plane of 
 the other two. The error in the drawing made by using this latter method, which is the better of 
 the two, will not be perceptible. The figures for the pitch diameter would of course be figured 
 
 correctly. 
 
 As in the preceding problem, this study should be anticipated by first gaining a thorough 
 
 knowledge of the lathe and its operation.
 
 Plate 1.
 
 Plate 1 
 
 1— -^i -H 
 
 7%3. 3 /S93
 
 Plate 2.
 
 Plate 2 
 
 ^^ 
 
 »^^^ 
 
 r-^~-, Sf. 
 
 .Mk. 
 
 L m 
 
 -v-^-" 
 
 
 /:^[Sro7^ze CA&ci^l^&e.,
 
 Plate 3.
 
 Plate 3 
 
 '/Globe i/alve 
 lie full Size 
 • 1 2. /89S
 
 Plate 4.
 
 Plate 4 
 
 Fig. 4
 
 Plate 5.
 
 Plate 5 
 
 CONNECTING ROD END. 
 SCALE FULL SIZE. 
 SEPT 6 1833
 
 Plate 6.
 
 Plates 
 
 Ju/if26 /893
 
 Plate 7.
 
 PtATE? 
 
 TWO 8E/*RIN(> NUTS. one; DRIVING- PULLEY. OI^E LOOSE PuLlEY. 
 
 ^ iSCREW POLISHING 
 
 MACHINE. 
 
 J iC AST IRON DETAILS, 
 
 +f H SCALE FULL SIZE. 
 
 AUG.I2.I893
 
 Plate 8.
 
 Plates 
 
 one: tail scrcw 
 
 OME REAR BEARING. 
 
 ONE e'SonT bearing. 
 
 — Z^i 
 
 r^6- - ,r 
 
 
 
 ^ ^f^ 
 
 ONEWASHEB TWO CAPS OME N'UT SCREW. ONE CENTCR DRIVE ONECENTER 
 
 ONESPRIN& Nol7WIRE. ONE ORIVIiM&PULLfy ONE LOOSE PuulEy 
 
 ^ri 
 
 ^*- 
 
 SCHEW. 
 
 T 
 
 HAADEN % GRIND 
 
 16 ,U.^p 
 
 "^ 
 
 1 
 
 
 SCREW. 
 
 T I ri 
 
 
 1^- 
 
 jL 
 
 ^ -t 
 
 a DCN C- GPi N O 
 
 ONE SPINDLE. 
 
 SCREW POLISHINGMACHINE 
 STEEL FORGING DETAILS. 
 SCALE FULL SIZE 
 AUG 12.1893
 
 Plate 9.
 
 Plate 9 
 
 "vt 
 
 J L 
 
 -rt 
 
 
 ^^ 
 
 11. 
 
 
 
 ijjj 
 
 - -w 
 
 ^ 
 
 r r- 
 
 ±1 
 
 
 K^- 
 
 Sco\e ". ^\x\\. S\.xe.
 
 Plate 10.
 
 Plate 10 
 
 Cross/iecj 
 rSco/e : 3fnc/ieS'=J/oot.
 
 Plate 11
 
 Plate 11. 
 
 Plate 1 1 
 
 Sact^vo n <7tt C,3: 
 
 17"XJatfic. 
 OaltSiock. 
 
 Oc\.2.\&90,
 
 Plate 12.
 
 Plate. 1 2 
 
 Co^G — Ca.^t Iron. 
 
 ^'^T^ 
 
 //ecc*/ — Oust -/V<??7 
 
 ^e.a</ StocAr JDeMfU Se^^^ sS^/8^^
 
 Plate 13.
 
 Plate. 13 
 
 r/6li 

 
 Plate 14.
 
 Plate 1 4 
 
 -.£s^lLXr ^'f ■ ^p^-'^J^'^-^ct9t-:o... ^ ^^r" ^'^^J/% ^^""^s.fef.'^ .r-/,<"'*— s)s^t.'M 
 
 
 
 ^//////.'///y/. y. 
 
 /'/ >»« /• ■ ,. < . ri g . /^-a 
 
 wmmm : in 
 
 
 
 
 St^&Z 
 
 Spin.uZe.Qeo.^ Cast Iro-rv 
 
 ^ £ 3 > 
 
 Quill Qear. ~ 'Cast 7,x>ri 
 
 
 
 Q-Lc^Zl—C'cLSi jTon, 
 
 ^&ci/^ SCocA:J)e£a,ils. 
 Se^^ JB^'' ■.■rf3. 
 
 zLocZ /Vt^C-S^e^T
 
 Plate 15.
 
 Plate 15 
 
 FlG.1 
 
 Fig. 2 
 
 Fig. 3 
 
 Fig. 4 
 
 ''/ 
 
 
 
 
 '//////V///// 
 
 Fig. 5 
 
 Fig 6 
 
 Fig. 7 
 
 Fig. 8 
 
 
 VISIBLE LINE 
 
 
 y/ / /j " " ^ '//^ '/ 
 
 VISIBLE LINE [SHADED] 
 
 INVISIBLE LINE 
 
 CENTER LINE 
 
 
 IMAD-INflRY LINE 
 
 
 FIGURE LINE 
 
 -> 
 
 Fig. 9 
 
 Fig.1 1 
 
 Fig. 10
 
 Plate 16.
 
 Plate 16 
 
 FiG.2 
 
 Fig. 3 
 
 FlQ.1 
 
 
 W 
 
 
 
 
 
 
 
 — 1 
 
 W 
 
 m 
 
 FiG.4 
 
 Fig. 5 
 
 Fig. 9
 
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