Mechanical Drafting 
 
 REVISED IN 1915 
 
 By 
 
 THE DEPARTMENT OF GENERAL ENGINEERING DRAWING 
 
 H. W. MILLER, M.E. 
 
 R. K. STEWARD, C.E. F. M. PORTER, M.S. 
 
 H. H. JORDAN, B.S. H. O. RUGG, C.E. 
 
 R. CRANE, S.B. C. A. ATWELL, B.S. 
 
 In the University of Illinois 
 Urbana, Illinois 
 
 (Original edition by H. W. MILLER) 
 
 The Manual Arts Press 
 Peoria, Illino is 
 
Copyright, 1912 
 
 H. W. Miller and R. K. Steward 
 Copyright, Revissd Edition, 1916 
 
 H. W. Miller 
 Fifth Edition, 1918 
 
PREFACE 
 
 In writing the original edition of this text it seemed 
 wise to the author to base its arrangement and content 
 upon two principles which considerable experience 
 proved sound. These principles are: first, that the stu- 
 dent can just as well and perhaps better, be taught the 
 use of instruments on work that will at the same time 
 have educational value; second, that for greatest effi- 
 ciency in teaching drawing the text should be made so 
 complete and follow the class room work so closely that 
 lecturing is unnecessary. 
 
 The above principles were followed by first design- 
 ing a very flexible course in drafting, substituting draw- 
 ings of machine parts for the conventional geometrical 
 figures. The work was arranged into definite groups, 
 according to subject, each group being scheduled for a 
 definite amount of time. Second, the text was so ar- 
 ranged that section, lesson or chapter one, gave all 
 information necessary for the work included in group 
 one, etc. 
 
 After three years' very satisfactory trial of the text, 
 the department of drawing has undertaken a complete 
 revision with the desire that the work shall be not only 
 a text, more complete than the first, but also a book of 
 reference that will be of service after the student has 
 completed the course. H W M 
 
 October, 1915. 
 
 405431 
 
CONTENTS 
 
 PAGE 
 
 Chapter 1. Lettering, Freehand and Mechanical 7 
 
 Chapter 2. Use of Instruments 29 
 
 Chapter 3. Orthographic Projection 52 
 
 Chapter 4. Working Drawings 65 
 
 Chapter 5. Fasteners, Threads, Bolts and Nuts, etc 88 
 
 Chapter 6. Shop Terms, Tools, Machines, etc 106 
 
 Chapter 7. Isometric and Oblique Projection 125 
 
 Chapter 8. Machine Sketching 147 
 
 Chapter 9. Perspective 151 
 
 Appendix 161 
 
MECHANICAL DRAFTING 
 
 CHAPTER 1 
 
 LETTERING 
 
 FREEHAND 
 
 (1) Freehand or offhand lettering is so much a part 
 of every engineer's daily routine that to be unable to 
 letter with speed and grace is considered an inexcusable 
 discredit. The results of practice show that no one need 
 be embarrassed long because of the lack of this skill, for 
 anyone can learn to letter. However, the acquisition of 
 proficiency demands what skill in any manual perform- 
 ance requires, more or less experience and careful study 
 of principles. 
 
 It is fortunate for the beginner in lettering that there 
 are very few elements that must be mastered. Most 
 engineers use extremely simplified styles of freehand 
 letters. The Reinhardt alphabet (slant or vertical) is 
 especially noted for its simplicity as it has been stripped 
 of all superfluous appendages that made formed styles 
 both complicated and time-consuming in their use. In 
 the practice of either type the beginner will find that all 
 of the letters are made up of but two or three charac- 
 teristic elements or strokes, each of which is easily 
 constructed. 
 
 The first style or type presented is the Eeinhardt 
 slant. It should be mastered thoroly because it is in use 
 in most drafting rooms and colleges. It is probable that 
 its use in over eighty per cent of the large drafting rooms 
 
.MECHANICAl; DRAFTING. 
 
 of the country is due to its legibility and ease and 
 rapidity of construction. 
 
 EQUIPMENT 
 
 (2) Selection of Lettering Pens. For a pure type of 
 either Eeinhardt or vertical letter, such a pen should be 
 used as will give a stroke of uniform width, weight, or 
 heaviness, when it is moved up, down, right, left, or diag- 
 onally on the paper; otherwise the letter will have a 
 shading, which does not belong to the types mentioned. 
 
 Fig. 1 
 
 Some pens which have proven satisfactory for letters 
 of a uniform weight are the Sheppard lettering pen, 
 Paysant pen, Moore's Non-Leaking fountain pen, and 
 any of the steel points known as ball pointed pens. 
 
 Inking of Pens. Apparently a great part of the 
 trouble experienced in the use of the above pens is due 
 to improper inking* No lettering pen should ever be 
 dipped into the ink bottle. The proper method is to 
 transfer by means of the quill attached to the cork a 
 small amount of ink to the inside of the ball pointed pen 
 or between the nibs of the Sheppard or Paysant pens. 
 
LETTERING. 9 
 
 It is well to hold the pen point over the bottle so that any 
 superfluous ink may not be spilled on the drawing or 
 desk. The word of warning that must be heeded is to 
 use only enough ink and no more. One may be sure of 
 not having too much ink on the ball pointed pen if he 
 will always stroke off the pen upon the quill before 
 trying any letters. 
 
 Slope Guide. Immediately on beginning practice on 
 inclined freehand letters it will be well to provide oneself 
 with a sheet of heavy drawing paper, about three by 
 eight inches, across which have been ruled a series of 
 heavy parallel lines at from 70 to 75 to the long edge 
 as shown in Fig. 1. These lines should be at equal inter- 
 vals and from one-eighth to one-quarter inch 
 apart. An angle of approximately 72 may 
 easily be constructed by laying off a right 
 triangle whose base is 2 and altitude 6, Fig. 2. 
 If this sheet, which may be termed a slope 
 guide, be laid just below the line on which 
 the freehand letters are to be made, it will 
 not be difficult to make all first element 
 strokes parallel, to each other. It is likewise 
 well to make use of such a guide continually 
 until this slope has become perfectly natural, for nothing 
 so detracts from the good appearance of inclined letters 
 as a difference in slope of the stems. 
 
 Paper. A good quality of ledger paper will be found 
 best for lettering, inasmuch as it has a smooth, hard 
 surface that takes ink evenly. It is likewise well to adopt 
 a standarji letter size sheet, 8%xll, which will be found 
 in stock in any printing office or stationery store, and to 
 
10 MECHANICAL DRAFTING. 
 
 which all modern office files are adapted in case one 
 wishes to file the finished work. 
 
 PRACTICE ON ELEMENTS 
 
 (3) Guide Lines. Unless especially printed practice 
 sheets have been prepared, the beginner should rule on 
 the blank sheet a series of six light parallel pencil lines 
 (preferably parallel to the short edge of the sheet) at 
 intervals of one inch and six at intervals of one-half 
 inch. 
 
 i nun 1 1 in i 
 
 Element Number I. 
 
 HHHHHH 
 
 Element Number . 
 
 Fig. 3 
 
 First element, Stems. Element one is simply a 
 straight line of varying length, Fig. 3, and making an 
 angle with the vertical equal to the slope adopted for 
 the inclined alphabet. In practice this slope can easily 
 be secured by placing the slope guide just loeneafh the 
 guide line on which one is working. Several lines of 
 stems should be made on the practice sheet, using the 
 half -inch guide lines, each with a single downward stroke 
 of the pen and at equal intervals. When finished the 
 sterns should all have the same slope, be evenly spaced 
 and each have the same weight or thickness thruout its 
 length and all stems of the same weight. 
 
LETTERING. 
 
 11 
 
 Second element, Ovals. The second element is a per- 
 fect ellipse, inscribed in a parallelogram, two of whose 
 sides are parallel to element one and whose base is, for 
 normal letters, a little less than the vertical height, Fig. 3. 
 This element can be made with one stroke of the pen, 
 after some little practice; however, it is advisable for 
 the beginner to form it 
 with two strokes, as shown 
 in Fig. 4, making slightly 
 more than half each time 
 and letting the ends of the 
 strokes overlap. This will in general insure a better 
 joint, as the overlapping tends to smooth out the juncture. 
 
 Fig. 5 
 
 In order that one may learn the shape of element 
 number two in the least possible time, it is suggested 
 that a beginning be made as shown in Fig. 5, with the 
 height of the character one inch. Using the one-inch 
 spaced guide lines already on the practice sheet, rule a 
 series of parallelograms, bases one inch and sides 
 inclined at the slope angle. Then sketch in long sweeping 
 arcs tangent to the inclined sides at their middle points, 
 a, Fig. 5; next follow the arcs tangent to the horizontal 
 sides, b, Fig. 5. The completed shape now suggests itself, 
 c, Fig. 5, and a few smoothing up strokes will complete 
 the ellipse, d, Fig. 5. It should be remembered that the 
 
12 
 
 MECHANICAL DRAFTING. 
 
 ellipse is tangent to the sides of the parallelogram at 
 their middle points; this gives the necessary tip that is 
 essential to a graceful appearance of the alphabet. 
 
 (a) (a) fc) ( C ) 
 
 Compressed Normal E.*-hen<Jed. 
 
 Fig. 6 
 
 An excellent variation of this exercise is that of 
 making ellipses of varying widths. It is evident, Fig. 6 7 
 that this process will yield alphabets of widely differing 
 general effect, altho the elements entering into their 
 construction are identical. The types of letters produced 
 by the varying widths are as indicated, compressed, nor- 
 mal, and extended. 
 
 The sketch* exercise just outlined should be repeated 
 with diminishing heights of three- fourths, one-half, one- 
 fourth, and finally one-eighth of an inch, the size ordi- 
 narily used in drafting. 
 
 oadqbpcey 
 
 Fig. 7 
 
 FORMATION OF LETTERS 
 
 (4) In Fig. 7 it is seen that the lower case letters 
 o, a, d, q, b, p, c, e, and y, and capitals C, G, 0, Q, Fig. 10, 
 are simple elements or combinations of elements one and 
 
LETTERING. 13 
 
 two. Element one and a portion of element two make 
 up lower case letters g, y, j, f , n, h, m, r, s, and u, Fig. 8, and 
 
 Fig. 8 
 
 capitals B, D, J, P, R, S, and U, Fig. 10. The remaining 
 straight stroke letters, i, k, 1, t, v, w, x, and z, Fig. 9, and 
 A, E, F, H, I, K, L, M, N, T, V, W, X, Y, and Z, Fig. 10, 
 
 iklfvwxz 
 
 Fig. 9 
 
 are perhaps easiest to construct. It shoulcj be noted that 
 the lower case letters a, c, e, etc., are two-thirds the height 
 of the capitals. The letter t is, five-sixths height and 
 
 abcdefghijklmnopqrstu 
 1 2.345 vwxyyz O789O 
 
 ABCDEFG H IJ KLM N 
 O PQ RSTUVWXYZ 
 
 Fig. 10 
 
 b, d, h, etc., are full height. The tails of the letters g, 
 j, p, q, etc., extend below the base line one-third their 
 height. Numerals are the full stem height except when 
 used in fractions when they should be shortened slightly. 
 See Fig. 10 for complete slant alphabet and numerals. 
 
14 MECHANICAL DRAFTING. 
 
 VERTICAL LETTERS 
 
 (5) In Fig. 11 is given an alphabet of vertical let- 
 ters. The principles of construction are of course iden- 
 tical with those of inclined letters. Practice should 
 begin on the two elements, stems and ovals, as directed 
 in Art. 3. No vertical guide will be necessary in this 
 
 abcdefghijklmnopqrstu 
 
 12345 vwxyz 6789 
 
 ABCDEFGHIJKLMN 
 
 OPQRSTUVWXYZ& 
 
 Fig. 11 
 
 case, inasmuch as everyone has a well developed sense of 
 appreciation of the vertical. It may be well to mention* 
 that when using vertical letters, an extended style, similar 
 to c or d, Fig. 6, is always easiest of execution and has an 
 excellent appearance. 
 
 MECHANICAL LETTERS 
 
 (6) The need for letters made entirely with instru- 
 ments will be only occasional, and space will be given 
 here for only the general methods for laying out such 
 work. In the appendix will be found alphabets of vari- 
 ous styles for use in the construction of titles, signs, 
 name plates, etc. These may be constructed either 
 mechanically or freehand, as desired. 
 
LETTERING. 
 
 15 
 
 Unit Space. If any given height which may be 
 assigned to a letter be divided into six equal parts (for 
 methods see Fig. 12) each of these parts is termed a 
 
 5 t /\ 
 
 b\/ \ \ A 1 is any 
 
 &/\ \ \ chosen distance 
 
 52 
 
 \ \ \ \ 
 
 \ \ \ \ 
 
 
 \ \ \ \ 
 \ \ l 
 
 Zj v . 
 
 i i i : 
 
 A 1 2 
 
 3 4 5 c 
 
 Fig. 12 
 
 unit space. It will be noticed in Fig. 13, which is of the 
 mechanical vertical Gothic alphabet most commonly used 
 by engineers, that all stems are of equal width, that is, 
 
16 
 
 MECHANICAL DRAFTING. 
 
LETTERING. 
 
 17 
 
 one unit. Either an extended or compressed style of 
 letter may be obtained by arbitrarily increasing or 
 decreasing the unit. 
 
 CONSTRUCTION OF LETTERS 
 
 (7) In constructing a word or series of words, the 
 rectangles w r hich will enclose the individual letters can 
 be laid out most rapidly by the method shown in Fig. 14. 
 The vertical distance at the left extremity of the line is 
 
 Fig. 14 
 
 first divided into six units. Any desired number of units, 
 e. g., 5 for the letter H, may then be carried any distance 
 to the right, by means of the T-square, to the left side 
 of the H rectangle, and then by means of the 45 triangle 
 to the upper guide line, thereby obtaining the location 
 of the right side. of the rectangle. The unit width of 
 letter stems and other necessary construction may also 
 be secured thru the proper use of the 45 triangle as 
 shown in Fig. 14. 
 
 For letters involving arcs of circles, after the enclos- 
 ing rectangles have been drawn, the centers may easily 
 be located as shown in Fig. 14 and as indicated for other 
 similar letters in the Gothic alphabet, Fig. 13. 
 
 In the construction of the letters B, E, F, H, R, and 
 S, it should be noted that the intermediate horizontal 
 stroke is slightly above the center; for A, G, and P it 
 
18 
 
 MECHANICAL DRAFTING. 
 
 is below. The letters B, E, R, S, X, and Z, and the nu- 
 merals 2, 3, 5, 6, 8, and 9, Fig. 15, will have a more pleas- 
 ing appearance if the width of the top section is less 
 than that of the bottom. 
 
 The distance d may vary from 1/6 to 1/4 
 
 Fig. 15 
 
 SPACING 
 
 (8) Having learned the correct shapes of the indi- 
 vidual letters, it becomes necessary to direct particular 
 attention to their combination into words and sentences 
 
LETTERING. 19 
 
 in headings, signatures, titles, name plates, etc. While 
 it may be aptly said that beautifully formed letters can 
 result only by a process of designing each stroke as it is 
 executed, this is more especially true of the completed 
 title page or other group of letters, taken as a whole, 
 where as much judgment is employed in the determi- 
 nation of the areas to be left white as those to be made 
 black. 
 
 Methods of Areas. As a help in securing good spacing 
 by eye alone, a rule that has proven very good is that of 
 making the total areas between successive letters appear 
 equal. It is well to adopt a specific area for this unit. 
 The best unit area is about one-third of the area of the 
 letter M; this is equivalent to a linear spacing of 2 units. 
 
 KEY TO TABLE, FIG. 16. 
 
 To obtain the space, in units, to be allowed between any 
 letter, e. g., A, and any letter of the alphabet which may 
 follow it in a word, it is seen in the table, Fig. 16, that 
 between A and BDEF, etc., one unit space should be left 
 and between A and CGO, etc., one half unit. In every 
 case the spacing given is that to be allowed between the 
 letter given in the first column and any letter of the 
 alphabet which may follow it in a word. 
 
20 
 
 MECHANICAL DRAFTING. 
 
 
 2 
 
 1% 
 
 1V4 
 
 1% 
 
 1 
 
 % 
 
 V 2 
 
 W 
 
 
 
 Neg. 
 
 A 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 AX 
 
 JTW 
 
 VY 
 
 B 
 
 
 
 BDEFHI 
 KLMNPR 
 
 COOQSC 
 
 Z 
 
 X 
 
 AJTWT 
 
 \ 
 
 
 
 C 
 
 
 
 BDEFHI 
 KLMNPR' 
 
 CGOQSD 
 
 Z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 D 
 
 
 
 BDEFHI 
 KLMNPR 
 
 CGOQSD 
 
 Z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 E 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 COOQSD 
 
 z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 F 
 
 
 
 
 
 
 BDEFHJ 
 KLMNPR 
 
 D 
 
 COOQST 
 VWXTZ 
 
 
 AJ 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 COOQSC 
 
 Z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 B 
 
 1BDEFH1 
 KLMNPR 
 
 
 
 CGOQSZ 
 
 X 
 
 AJTWT 
 
 v 
 
 
 
 
 
 I 
 
 BDEFH] 
 KLMNPR 
 
 
 
 COOQS2 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 
 
 J 
 
 
 BDEFH1 
 KLMNPR 
 
 C 
 
 COOQSZ 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 
 K 
 
 
 
 
 BDEFHI 
 KLMNPrf 
 
 D 
 
 COOQSZ 
 
 X 
 
 AJTWT 
 
 V 
 
 
 L 
 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 A'COOQS 
 XZ 
 
 J 
 
 TVWT 
 
 M 
 
 BDEFHJ 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 X 
 
 A.JTWT 
 
 V 
 
 
 
 
 
 N 
 
 BDEFH1 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 X 
 
 A.ITWT 
 
 V 
 
 
 
 
 
 
 
 
 
 BDEFHJ 
 KLMNPR 
 
 COOQSD 
 
 Z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 P 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 TVWXT 
 
 AJ 
 
 
 Q 
 
 
 
 BDEFHI 
 KLMNPB 
 
 COOQSU 
 
 Z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 R 
 
 
 
 BDEFHI 
 KLMNPR 
 
 COOQSD 
 
 2 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 S 
 
 
 
 BDEFH! 
 KLMNPR 
 
 COOQSU 
 
 Z 
 
 X 
 
 AJTWT 
 
 V 
 
 
 
 T 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 TVWXT 
 
 A 
 
 J 
 
 D 
 
 
 BDEFH1 
 KLMNPR 
 
 
 
 COOQ9Z 
 
 X 
 
 AJTWY 
 
 V 
 
 
 
 
 V 
 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQST 
 VWXTZ 
 
 
 AJ 
 
 w 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 TVWXT 
 
 A 
 
 J 
 
 X 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 X 
 
 AJTVW 
 T 
 
 
 
 Y 
 
 
 
 
 
 BDEFHI 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 TVWXT 
 
 
 AJ 
 
 z 
 
 
 
 jBDEFHl 
 
 KLMNPR 
 
 D 
 
 COOQSZ 
 
 X 
 
 ATVWT 
 
 3 
 
 
 
 Fig. 16 
 
LETTERING. 21 
 
 Special Cases. The method of areas just suggested 
 can be easily applied in spacing the complete rectangular 
 letters, H, M, etc.; and after some practice will not be 
 found difficult for the curved letters. There are, how- 
 ever, letters which require attention in almost every 
 
 LAFAYETTE 
 
 Fig. 17 
 
 arrangement in which they occur. In Fig. 17 is shown 
 a word involving A, F, L, T, and Y, all of which, 
 together with J, P, and V, are difficult to combine with 
 other letters and maintain good spacing because they 
 differ so greatly in width at the top and bottom. When 
 L comes before A it is wise to decrease its width one-quar- 
 ter unit. So, also, when T follows F, P, T, V, W, or Y, its 
 width should be reduced one-quarter unit. A after F and 
 before or after T, V, W, or Y, should be set much closer 
 than when used with other letters, in some cases the 
 spacing being even negative, i. e., the F overlapping the 
 A, Fig. 17. Other changes will suggest themselves. 
 
 Crowding Letters. One of the common errors made 
 by beginners is that of crowding the straight stroke 
 
 MINING Ml NINO 
 
 Approved Spacing 
 Incorrect Spacing 
 
 Fig. 18 
 
 letters too close together and separating the oval letters 
 too far; this always results in making the inking look 
 heavier in some places than in others, Fig. 18. 
 
2Z MECHANICAL DRAFTING. 
 
 Spacing of Compressed and Extended Letters. In the 
 latter part of Art. 3 it was shown that wide variation in 
 the resulting appearance of an alphabet may be secured 
 by modifying the proportions of the oval element. It 
 should be kept in mind, when performing an exercise in 
 any altered style, that good appearance, i. e., uniformity 
 of shapes, equality of spacing, smoothness of effect, can 
 be produced in only one way: All letters and spaces 
 must be reduced or enlarged in the same proportion. 
 That is, if the letters are decreased one-third their normal 
 widths then the values given in Fig. 16 must be decreased 
 one-third also, in order to give the proper spacing to be 
 used. Thus, suppose the word shown in Fig. 19 (a) , if con- 
 structed of normal letters, is found to be either too long 
 or too short for the space available for it. In (b) and. 
 (c) of this figure are shown the same word constructed 
 
 TERMINAL STATION TERMINAL STATION 
 
 (b) 
 
 (e) 
 
 Fig. 19 
 
 in compressed and extended styles respectively. In each 
 form, however, it will be seen that the distance between 
 "straight stroke letters, as that between M and I, conforms 
 to that prescribed in Art. 8; that is, it is one-third the 
 width of the letter M. The values given in the table, 
 Fig. 16, may be used directly by simply taking as the unit 
 for spacing one-sixth the width of the M in the particular 
 style used. The stems of compressed and extended let- 
 ters have the same width as the stems of normal letters, 
 i. e., one-sixth of the height. The method here outlined 
 is applicable to both vertical and slant styles. 
 
LETTERING. 23 
 
 Mechanical Spacing. In the table, Fig. 16, is given in 
 terms of a sub-division of the standard unit space, the 
 spacing that is approximately correct, according to good 
 design, for any combination of letters. If this table be 
 given some careful study in connection with the principle 
 explained in the paragraph, "Method of Areas," it will 
 be possible after some little practice to design rapidly 
 without constant reference to the table for the correct 
 spacing. 
 
 NAME PLATES 
 
 (9) Definition, A name plate is a small metal plate 
 fastened to a machine or structure and should contain 
 the following information : Name of the machine (unless 
 it is so common as to be perfectly familiar to everyone), 
 name of the manufacturing company, and address or 
 location of the company's works or factories. 
 
 DRAWING TITLES 
 
 (10) Definition, A working drawing title is a con- 
 densed statement of the following information: Name 
 of the piece of machinery drawn, name and address of 
 the manufacturing company, initials of the draftsman, 
 checker, and tracer, scale, drawing number, and other 
 necessary filing data. 
 
 GENERAL ORDER OF WORK IN CONSTRUCTION OF 
 WORKING DRAWING TITLE 
 
 (11) Given data. In making up a working drawing 
 title the draftsman ordinarily has given him a certain 
 amount of data as follows : ' ' Details of Horizontal Mill- 
 ing Machine, manufactured by the Landis Tool Company, 
 Waynesboro, Penna.; drawn by (K. C. S.), checked by 
 ( ), traced by ( ), scale y 2 "=l", draw- 
 
24 MECHANICAL DRAFTING. 
 
 ing finished April 2nd, 1915. " The above material, con- 
 densed, must be placed within a given title space, per- 
 haps 3"x5". 
 
 Elimination of unnecessary material and arrange- 
 ment into groups. In order that the given material may 
 be placed within the given title space, every unnecessary 
 word must be eliminated. Eunning thru the given data 
 it is seen that the words italicized can be omitted 
 without the least danger of misunderstanding the 
 remainder. With these words omitted the remaining 
 data seems to group itself naturally as follows: 
 
 (1st prom.) Horizontal Milling Machine. 
 
 Details 
 
 (2nd prom.) Landis Tool Co. 
 
 (3rd prom.) Waynesboro, Pa. 
 
 Drawn by ( ), Checked by ( ), Traced by ( ), 
 
 (4th prom.) Date ( ), Scale ( ). 
 
 Order of prominence. In a drawing title as well as 
 in a name plate, certain groups of words are more impor- 
 tant than others. In the drawing title the name of the 
 piece of machinery is, of course, given most prominence ; 
 while, in the case of the name plate the name of the manu- 
 facturing company should be given first prominence. In 
 the drawing title the name of the manufacturing com- 
 pany will be given second prominence, address of the 
 company third, and the remaining information, being 
 about equally important, should be given least prom- 
 inence and arranged as desired. The word "Detail" or 
 " Assembly ", which may be either included or omitted 
 as desired, will not figure in the order of prominence. 
 
LETTERING. 25 
 
 Methods of securing prominence. In both advertis- 
 ing and drafting there are in use two methods for secur- 
 ing prominence of any one group of words over another. 
 The one most generally used is variation in height of 
 the letters of the various groups, to correspond in general 
 to the order of prominence established; if this is not 
 possible thru lack of space, a distorted letter, either of 
 odd construction or of the compressed or expanded style, 
 may be used. One may then depend on the odd appear- 
 ance of the letters to give to that group of words the 
 desired prominence. In the case of drawing titles and 
 name plates the first method, i.e., variation in height of 
 letters is preferable. 
 
 Margins and margin lines. Before sketching in the 
 guide lines for the various groups of words, margin 
 spaces should be determined and light margin lines ruled 
 in Fig. 20. In doing this certain rules of design must be 
 adhered to ; the upper and lower margins may be of any 
 desired width; however, for best appearance they must 
 be equal. The right and left margins, tho not necessarily 
 equal to the upper and lower, must be equal to each other. 
 In a rectangular space whose width is greater than the 
 height, better effect is obtained if the right and left mar- 
 gins are made slightly greater than the upper and lower; 
 if the reverse is true of the rectangle then the right and 
 left margins should be less than the upper and lower. 
 
 Guide lines. To obtain the guide lines for the various 
 groups of words, produce the lower margin line to the 
 left until it intersects the border of the title space at A, 
 Fig. 20, and .from this point draw up and toward the 
 right a line at an angle of about 60 degrees with the 
 horizontal. Selecting any desired distance a: the rela- 
 
MECHANICAL DRAFTING. 
 
 H 
 
 Q 
 
 ^ 
 
 i in 
 
 
 
 
 b 
 
 p 
 
 o 
 
 t 
 
 D 
 
 DQ 
 
 m 
 
 AV 
 
 ;.u 
 
 ! 8 
 
 fe 
 
 IE 
 
 9? 
 
 Q) 
 
 & 
 P 
 
LETTERING. 27 
 
 tive height of the letters of the lower group, lay off this 
 distance from A along the 60 degree line; then a relative 
 distance for the space between this line and the line next 
 above; next a relative space for the letters of the next 
 group and so on until all of the groups have been 
 accounted for along the 60 degree line. From the last 
 point, B, draw a line, B C, as shown in figure and from 
 the various points along the line A B draw lines parallel 
 to B C until they intersect the border line, A C; the re- 
 quired guide lines will then be found the same relative 
 distances apart as the points plotted on the line A B. 
 
 W ' A 
 
 Y 
 
 N 
 
 ' E ' 
 
 5 ' ' fl ' 
 
 Scratch 
 
 " R " ' 
 
 Paper 
 
 1 P " A \ 
 
 _^* 
 
 Guide Lines 
 
 : ,3 o 
 Scratch Paper 
 
 Fig. 21 
 
 Spacing of letters. Before attempting to place in any 
 of the letters the value of the unit spaces of the various 
 groups of letters must be determined. Tho the various 
 lines of letters may not require all of the horizontal space 
 allotted to them, for best appearance they must be placed 
 centrally ; i.e., with equal margins at their right and left. 
 To accomplish this, rule in a vertical center line of the 
 title space and use the following method : 
 
 Scratch paper method. Select any point close to the 
 left end of the straight edge of a sheet of scratch paper, 
 
28 MECHANICAL DRAFTING. 
 
 Fig. 21, and from this point step off with the large and 
 small dividers the proper number of unit spaces in suc- 
 cession, for the various letters and spaces between letters, 
 marking with the divider points the location of the 
 beginning and end of each letter. Placing the scratch 
 paper centrally along the lower guide line of the space 
 into which this group of letters is to go, mark with the 
 needle point the position of the beginning and end of 
 each of the letters. This method has the advantage of 
 centrally placing the entire group and of locating the 
 various letters at the same time. 
 
 If the letters are to be free hand the above method 
 will be found equally useful. Instead of laying off the 
 spaces in units, the letters themselves should be sketched 
 on the scratch paper and the group placed centrally as 
 before. The style of letters to be used, i.e., normal, com- 
 pressed or extended, will be readily suggested by this 
 procedure. 
 
 Bill of material. On detail drawings where numerous 
 pieces are shown, a bill of material should be placed 
 above, and usually joined to the title. In general it 
 should contain in tabular form such information as 
 the number of pieces required, material made of, pat- 
 tern numbers, part numbers, name of pieces, and other 
 information. Examples of typical bill of material will 
 be found in the Appendix. 
 
 GUMMED LETTERS 
 
 (12) For those who have an appreciable amount 
 of work on titles, signs, etc., the gummed letters sold by 
 the Ticket and Tablet Company, of Chicago, and which 
 are shown in their exact sizes and styles in the appendix, 
 will be found a great convenience. The many uses which 
 such letters serve need not be enumerated. They are 
 made in .red, white, and black. 
 
USE OF INSTRUMENTS. 
 
 CHAPTER 2 
 
 USE OF INSTEUMENTS 
 DRAWING-BOAKD 
 
 (13) Construction. Drawing-boards are made of 
 either poplar or white pine, the right and left edges, Fig. 
 1, being reinforced by cleats of some harder wood. These 
 
 White pine or poplar 
 This side for 
 
 hard wood cleat 
 
 Under side for 
 trimming paper, etc. 
 
 DRAFTING ONLY 
 
 Fig. 1 
 
 cleats serve both as stiffeners and as runners for the easy 
 sliding of the T-square. The better grades of small 
 
 Saw cuts 
 
 Maple or celluloid strip 
 
 Battens 
 
 Fig. 2 
 
 boards are reinforced on the back by two battens, Fig. 2, 
 and ordinarily, have inserted in their right and left edges 
 a wearing strip of either hard maple or celluloid, instead 
 of the cleats of Fig. 1. It will be noticed in Fig. 2 that 
 
30 
 
 MECHANICAL DRAFTING. 
 
 the right and left edges of the second class of board 
 are broken at intervals by saw cuts which prevent the 
 inserted strip of hard wood from expanding and split- 
 ting the wood. 
 
 Use. The two sides of the type of board shown in 
 Fig. 1 have very definite uses if the board is to be kept 
 in shape for good drafting. The one side for drafting 
 
 / 
 
 
 J \ \ o| 
 
 [X Hi-ad of T-square ALWAYS to LEFT O | 
 
 V 
 
 
 Paper 
 
 Tacks about 1 /4" from 
 
 2 
 
 
 o 
 
 edges of sheet 
 
 s 
 
 
 
 1 
 
 
 
 1 
 
 
 
 t 
 
 
 
 
 ^osition when not in use 
 
 
 
 \ 
 
 
 \ 
 
 Fig. 3 
 
 only, the other for any necessary rough work, trimming 
 paper, etc. Never trim paper on the drafting side. 
 
 PAPER 
 
 (14) Quality. A novice cannot obtain good work 
 from poor material, hence it is imperative that the begin- 
 ner in drawing use the best quality of paper obtainable. 
 A heavy, hard surface paper of the quality of Keuffel & 
 Esser's Normal, or E. Dietzgen's Napoleon is recom- 
 mended. 
 
 Position of paper on board. In tacking the paper to 
 the board, Fig. 3, keep the sheet well toward the top and 
 
USE OF INSTRUMENTS. 31 
 
 to the left; about two and one-half inches from the upper 
 and left edges. This should be done in order that the 
 draftsman may work to advantage on the bottom of the 
 sheet, and that it may not be necessary to work to any 
 great extent on the end of the T-square blade, which 
 cannot be prevented from springing slightly. 
 
 Tacking sheet. Place upper left corner of sheet in 
 approximately correct position and tack to the board, 
 Fig. 3, placing tacks close to the corners of the paper. 
 Then after lining up the upper edge with the upper edge 
 of the T-square blade, stretch sheet and tack upper right 
 corner. The lower edges may be tacked down in any 
 order; or, after some experience, may be left untacked, 
 as these tacks have a tendency to interfere with the 
 T-square and triangles. 
 
 BOEDER LINES 
 
 (15) The border lines as well as all othe^ construc- 
 tion work done by the draftsman should be placed in by 
 measurements from center 
 lines and not from the 
 
 ol oorcler lo 
 
 edges of the sheet. In the 
 
 1 - i 
 
 case of the border lines, 
 the measurements are 
 made from the horizontal 
 and vertical center lines of 
 the sheet, Fig. 4. Fig 4 
 
 T-SQUARE 
 
 (16) Construction. Both the blade and the head of 
 the T-square, Fig. 5, are of hard wood, hence the glue 
 
32 
 
 MECHANICAL DRAFTING. 
 
 Walnut or Ebony Head 
 
 Fig. 5 
 
 cannot cement them very tightly together ; neither do the 
 short screws hold very firmly; a fall, even to the floor, 
 may break the joint and damage the T-square. Keep the 
 T-square out of danger of any such fall. 
 
 In case the joint 
 breaks, take out 
 screws, rough both 
 head and blade with 
 coarse sandpaper, 
 coat well with Denni- 
 son's glue, place 
 blade at 90 with head 
 with triangle, tighten 
 screws and let stand 
 a day. Then take out screws and put in round-headed 
 wood screws long enough to run through and project an 
 eighth of an inch or more. File off screws carefully. Be 
 sure screws are tight. It may be advisable to bore small 
 holes entirely through head and blade for these large 
 screws, to prevent splitting of the wood. 
 
 Position on board. In drafting, a right-handed man 
 should keep the head of the T-square to the left, Fig. 6, 
 in order that he may handle it with his left hand, leaving 
 the right free for drafting. Never place the T-square in 
 any other position on the board, as the edges of the board 
 seldom form a rectangle nor is the head of the T-square 
 likely to make exactly 90 degrees with the blade. 
 
 Use of blade. The upper edge of the blade should be 
 used for drafting only; and the draftsman will do well 
 to take excellent care of this edge, for once nicked or 
 
USE OF INSTRUMENTS. 
 
 33 
 
 dented the instrument is practically ruined for good work. 
 The lower edge may be used as a cutting ruler but never 
 for drafting. 
 
 Head ALWAYS to LEFT 
 
 Fig. 6 
 
 Position when not in use. Any draftsman profits by 
 keeping his drawing instruments in certain definite 
 places, so that as far as possible he may keep his atten- 
 tion entirely on his work, handling his instruments sub- 
 consciously. It is found most convenient to slip the 
 T-square to the bottom of the board, when not in use ; it 
 is here out of danger, out of the way, yet easily accessible. 
 
 To keep clean. A drawing may easily be smudged by 
 a dirty T-square, so it will be well to give the blade a 
 thoro cleaning with a damp cloth or piece of art gum at 
 frequent intervals. 
 
84 MECHANICAL DRAFTING. 
 
 SCALE 
 
 (17) Care. The scale should never be used as a 
 ruler because, as a drafting instrument its efficiency 
 depends upon the condition of its edges, and these edges 
 can easily be defaced by misuse and the instrument badly 
 damaged. Furthermore, the boxwood of which the scale 
 is made warps quite easily; hence, the edges of a tri- 
 angular scale will seldom be found perfectly straight. 
 
 Fig. 7 
 
 Use. On inspection, Fig. 7, it is seen that the numer- 
 als are all placed on the scale so as to appear upright 
 only when one works over the top of the scale or on the 
 edge away from the draftsman and not toward him. All 
 dimensions should be taken directly from the scale as it 
 lies on the drawing and not by means of the dividers. 
 The needle point is the best aid in obtaining dimensions 
 with perfect accuracy. The pencil point is a poor sub- 
 stitute for the needle point. 
 
 NEEDLE POINT 
 
 (18) From Richter type of instruments. An excel- 
 lent needle point for obtaining dimensions may be made 
 
USE OF INSTRUMENTS. 
 
 35 
 
 up by inserting into the long knurled barrel furnished 
 with every set of Eichter type of instruments, the small 
 point which is provided for converting the large compass 
 into a set of dividers, Fig. 8. 
 
 Fig. 8 
 
 To make in shop. A needle point may be easily made 
 from a strip of white pine I4:"xi4"x2" and a medium size 
 sewing needle. 
 
 Fig. 9 
 
 Construction: Fig. 9. Insert the needle in a vise, 
 point down, with about %" of the point in the vise, and 
 
36 
 
 MECHANICAL DRAFTING. 
 
 carefully drive the strip of pine over the exposed part 
 of the needle; the wood may then be shaved round and 
 pointed slightly at the needle end. 
 
 TRIANGLES 
 
 (19) In drawing vertical lines with triangles the ver- 
 tical edge should always be to the left or toward the 
 head of the T-square, Fig. 10. 
 
 To clean. The surface of the celluloid tri- 
 angles quickly becomes smudged from era- 
 sings and pencil dirt that may be on the 
 drawing; hence, they must be cleaned 
 
 
 
 Always Never 
 
 IV A 
 
 
 E- ' 
 
 \ 
 
 
 
 Fig. 10 
 
 Fig. 11 
 
 frequently with soap if the drawings are to be kept in 
 good shape. 
 
 Letter guide lines. For the easy ruling of letter guide 
 lines without the use of the scale and needle point, it is 
 suggested that along the edges of the 30x60 triangle 
 light lines be scratched with the needle point as follows : 
 Along the hypothenuse and 1/8" from the edge scratch 
 carefully a fine line; also a second line 3/1 6" from the 
 
USE OF INSTRUMENTS. 37 
 
 edge ; along the long leg scratch two lines 1/8" and 1/12", 
 respectively, from the edge, Fig. 11. After the lines 
 have been scratched they should be smeared over with 
 India ink, rubbing the ink into the scratches with the 
 fingers. After the ink has dried for a few minutes the 
 surplus may be rubbed off with a cloth. Turning the 
 triangles over with the scratched lines against the paper, 
 it is seen that they now stand out very sharply, and may 
 be used in ruling guide lines for any necessary lettering. 
 
 Parallel and perpendicu- 
 lar lines. In Figs. 12 and 13 
 are shown a number of meth- 
 ods of obtaining a series of 
 parallel lines, or lines per- 
 pendicular to given lines, by 
 means of the triangles and T-- 
 square. These figures should 
 be studied until their mean- 
 ing is quite clear, as the 
 methods here shown are the F . 12 
 
 most accurate known, and 
 
 are the only ones that will be recognized in the drafting 
 room. 
 
 PENCILS 
 
 (20) Numbering. Before sharpening either end of 
 the pencil, cut with a pen knife a number of nicks toward 
 the center to correspond to the degree of hardness ; e. g., 
 four nicks for 4H, six for 6H, etc., Fig. 14. 
 
 Sharpening wood. In sharpening, trim the wood 
 carefully on both ends of the pencil, back a distance of 
 
38 
 
 MECHANICAL DRAFTING. 
 
 about one inch from the ends, leaving about %" of the 
 lead exposed, Fig. 15. One end is to be sharpened to a 
 round point, the other to a wedge. In shaping up both 
 of these points, use the pencil point file provided in 
 the kit. 
 
 Fig. 13 
 
 Fig. 14 
 
 Round point. In shaping up the round point, hold 
 the pencil at an angle of about 45 degrees with the axis 
 of the file. As the lead travels over the file, Fig. 16, 
 revolve the pencil slowly between the thumb and fingers, 
 
USE OF INSTRUMENTS. 
 
 39 
 
 attempting to give it a complete revolution with each 
 stroke. The lead may thus be easily sharpened to a per- 
 fect cone. In this sharpening be careful that the point 
 extends the full length of the lead exposed. 
 
 Fig. 15 
 
 
 Fig. 16 
 
 Wedge point. In sharpening the wedge point hold 
 the pencil perpendicular to the axis of the file, Fig. 17, 
 
 JRound point 
 
 Fig. 17 
 
 and so inclined to the plane of the file that the lead may 
 be sharpened the full quarter inch exposed. 
 
40 
 
 MECHANICAL DRAFTING. 
 
 Use of points. The round point should be used for 
 drawing short lines -and lettering, the wedge point for 
 long lines; the round point dulls rapidly in drawing a 
 long line and will make a line of varying weight. 
 
 ERASERS 
 
 (21) If an eraser becomes apparently greasy and 
 smudges instead of cleans a drawing, it may easily be 
 cleaned by rubbing it with another eraser or by rubbing 
 it on the rough surface of the drawing-board itself. 
 
 Chamois roll 
 
 Fig. 18 
 
 CLEANING PADS AND BLOTTERS 
 
 (22) Chamois roll or block. Inasmuch as water 
 proof drawing ink dries so rapidly the pen should be 
 cleaned thoroly with cloth or chamois before each refill- 
 ing. In addition to this cleaning it will be found possi- 
 ble to obtain more clear cut work if after each three or 
 four lines the point of the pen is scraped over a piece 
 of chamois. A convenient cleaner may be made by roll- 
 
USE OF INSTRUMENTS. 41 
 
 ing up a 2"x 4" piece of chamois and binding it with a 
 rubber band, Fig. 18, or by pasting a 2"x 2" piece on a 
 small block of wood. 
 
 Blotters. Never attempt to blot drawing ink. , The 
 ink is too heavy to be absorbed by blotting paper. 
 Always permit the ink to dry. A puddle of ink may, 
 however, be removed by the careful use of the corner of a 
 blotter. 
 
 LARGE DIVIDERS 
 
 (23) Adjustment of the points. With the Richter 
 type of instrument, it will always be found possible to ad- 
 just the points of the various tools to any desired length; 
 so, before attempting to use the large dividers be sure that 
 the points are adjusted to exactly the same length and 
 that they are in perfect shape. In case the points of the 
 Gem Union instruments are not of the same length, it 
 will be necessary to grind the long point down on a small 
 carborundum stone. Keep points always in perfect shape 
 for good work. 
 
 Opening and setting. It is desirable always to handle 
 each instrument with the right hand unaided by the left; 
 this permits of much more rapid work and the habit is 
 not difficult to acquire. To open the divider, insert the 
 thumb between the legs, prying them apart a short dis- 
 tance until the fingers may be inserted and the one leg 
 grasped between the first and second fingers, the other 
 between the third finger and the thumb; the head of the 
 instrument should rest against the knuckle of the first 
 finger. Holding the instrument in this position it is 
 found easily possible to adjust the points to any desired 
 distance. 
 
42 
 
 MECHANICAL DRAFTING. 
 
 To place point. To place the one point of the divider 
 at any point on the sheet, rest the wrist at a convenient 
 distance from the point ; it will then be found easily pos- 
 sible to place the point of the leg between the third finger 
 and the thumb in any desired position. Baising the 
 wrist and keeping the little finger on the paper, the other 
 leg can now be adjusted for any desired distance. It is 
 perhaps as good practice and may be found easier for 
 some to steady the hand thruout the operation by merely 
 resting the little finger on the paper, instead of the wrist. 
 
 Stepping off distances. After the points have been 
 placed as desired, to step off a certain distance a num- 
 ber of times, raise the first finger to the top of the head, 
 then, releasing the other leg, grasp the head between the 
 first finger and the thumb and step off the distance by 
 swinging the dividers alternately over and under. Hand- 
 ling the instrument in this way it will not be necessary 
 to take a new grip on the head thruout the operation. 
 
 LARGE COMPASS 
 
 (24) Adjustment. To 
 adjust the needle point of 
 a compass to both the pen- 
 cil and pen, remove the 
 pencil point and insert 
 pen; after adjusting the 
 needle point so that its 
 shoulder, not the point, is 
 flush with the end of the 
 pen, remove pen and in- 
 serting pencil, adjust lead 
 until it is even with the shoulder of the needle point. 
 
 Wedge point 
 
 Fig. 19 
 
USE OF INSTRUMENTS. 43 
 
 Use. For adjustment of leads to any desired radius, 
 and placing needle point at any desired center, see Large 
 Dividers, Art. 23. For describing arcs with the large 
 compass the legs should be adjusted as shown in Fig. 19. 
 
 IRREGULAR CURVE 
 
 (25) The irregular curves are those which cannot be 
 drawn readily and accurately with the compass. The gen- 
 eral directions of the different portions of such curves are 
 first determined roughly by a number of plotted points 
 at as small intervals as possible (the positions of these 
 points are obtained either by mathematical coordinates 
 or mechanically from other projections or views of the 
 same curve). Before drawing the curve mechanically it 
 is best to draw lightly a freehand curve thru the plotted 
 points, then carefully piece by piece the mechanical 
 curve may be drawn. In drawing the mechanical curve 
 two things must be kept in mind; first, that the final 
 curve must coincide as absolutely as possible with 
 the freehand curve; second, that the curve must be 
 " smooth," i. e., it must have no sudden glaring changes 
 of curvature or "humps." The failure of a novice to 
 obtain a good irregular curve is due to perhaps two 
 causes: first, that he starts with the assumption that it 
 is too easy to require any attention, and second, that he 
 is too easily satisfied with a very indifferent job. Curves 
 having curious "humps" may be termed freaks and are 
 seldom, if ever, encountered in Mechanics. 
 
 It is difficult to recommend any curve or even several 
 curves as being even approximately universal, so no such 
 advice will be attempted. A great number of such curves 
 are listed in all instrument catalogs and special require- 
 ments will have to be depended upon in any selection. 
 
44 
 
 MECHANICAL DRAFTING. 
 
 However, two curves have found much favor among stu- 
 dents and are recommended for general use. One of 
 these has obtained the name of " Banana " curve, Fig. 20, 
 and the other is the G. E. D. Special, Fig. 21. 
 
 Banana 
 
 Fig. 20 
 
 Fig. 21 
 
 BOW DIVIDERS 
 
 (26) Adjustment. (See Adjustment for Large 
 Dividers.) 
 
 Placing at center. (See same for Large Dividers.) 
 
 Opening and closing points. With the center adjust- 
 ment instrument, which is always preferable to the side 
 
USE OF INSTRUMENTS. 45 
 
 adjustment, after placing the one point at a given point 
 on the sheet, raise the first finger to the head and turn 
 the adjustment screw between the second finger and 
 thumb until the points are apart as desired. 
 
 Stepping off distances. (See same for Large 
 Dividers.) 
 
 BOW PENCIL 
 
 (27) Hard lead. To obtain satisfactory work from 
 the boiv pencil the lead should be extremely hard, at least 
 6H. Ordinarily, the lead supplied with instruments is 
 not more than 2H or 3H, and wears down too rapidly. 
 Try the lead before using it on a drawing, and if found 
 soft, substitute for it a piece of lead from a 6H pencil. 
 
 Sharpening lead. Since the bow pencil is, like the 
 bow dividers, an instrument of precision, for small arcs 
 the round point will be found more 
 convenient than the wedge. Inas- 
 much as the total amount of use is 
 small compared with that of the 
 large compasses, the need of a 
 wedge point to diminish the number 
 of times required to shape it up, is 
 not great enough to overbalance the 
 inaccuracy and awkwardness of the 
 latter in drafting. It is well to Fig< 22 
 
 shape the point as long as the con- 
 struction of the instrument and the strength of the lead 
 will permit. Fig. 22. 
 
 Adjustment to any radius. In adjusting ihepoints to any 
 desired radius, instead of obtaining the dimension directly 
 
46 
 
 MECHANICAL DRAFTING. 
 
 from the scale, it will be better to transfer this 
 radius to the paper by means of the scale and needle 
 point, and set the bow pencil from 
 this as explained under Large Di- 
 viders. 
 
 Describing arcs. In describing 
 an arc with either the compass, bow 
 pencil or pen, the direction of mo- 
 tion of the lead should be clockivise 
 and thru the total length of the de- 
 sired arc before taking the point 
 from the paper, Fig. 23. 
 
 RULING PEN 
 
 (28) Manner of holding. The 
 ruling pen should be held between 
 the first and second fingers and 
 thumb as shown in Fig. 24. In 
 ruling lines, the adjusting screw 
 should be turned from the user. 
 
 Fig. 23 
 
 Position of pen. Unless care is 
 taken to keep the pen in a vertical 
 plane thru the edge of the T-square 
 blade or edge of the triangle, Fig. 25, trouble may be ex- 
 perienced in the ink running under the T-square blade, 
 Fig. 26, or in a badly broken line, Fig. 27. 
 
 Tilted in the direction of motion. For best results 
 the pen should be tilted slightly in the direction of the 
 motion, Fig. 24; this permits one to inspect the work of 
 
USE OF INSTRUMENTS. 
 
 47 
 
 the pen as it travels. A greater angle than 10 or 15 
 degrees may however permit the ink to run down and 
 cause a blot. 
 
 Fig. 24 
 
 Fig. 25 
 
 Effect of Position 2 
 
 Effect of Position 3 
 
 Ink ran under T square 
 Fig. 26 
 
 Pen riding on one nib 
 Fig. 27 
 
 To fill pen. To fill the pen, always use the quill sup- 
 plied on the stopper of the ink bottle. Never dip the pen 
 into the ink. If by chance any ink has gotten on the out- 
 side of the pen, wipe it off carefully before using; it may 
 save a serious blot. 
 
48 
 
 MECHANICAL DRAFTING. 
 
 Direction of motion in ruling lines. In ruling lines, 
 either with the pen or pen- 
 cil, the direction of motion 
 should be from left to right 
 or from bottom to top of the 
 sheet, Fig. 28. Euling lines 
 thus, it is always possible to 
 see what the pen or pencil 
 is doing. Never rule lines 
 down the sheet unless they Fig - 28 
 
 are oblique and are being put in with the triangle. 
 
 Paste sheets together 
 and cut to 6" diam. 
 
 Fig. 29 
 
 INK BOTTLES 
 
 (29) Holder. A convenient holder for the ink bot- 
 tle may be made from two sheets of blotting paper and 
 a rubber band as shown in Fig. 29. A holder of some 
 
USE OP INSTRUMENTS. 
 
 49 
 
50 
 
 MECHANICAL DRAFTING. 
 
 Fig. 30 
 
 kind is advisable and one such as this answers a double 
 purpose. A holder of the style shown in Fig. 30 may be 
 purchased from any of the instrument companies. 
 
 Closed when not in 
 use. India ink is very 
 heavy and dries quite 
 rapidly; hence, if the 
 stopper is left out of the 
 bottle even for several 
 hours the ink may be- 
 come so heavy as to 
 make it impossible to 
 obtain good work from 
 it. Be sure to close the bottle carefully after each refill- 
 ing of the pen. With proper treatment the ink will 
 remain in good condition for several years. 
 
 To open bottle and 
 fill pen. To open the 
 bottle without danger 
 of upsetting, grasp 
 the neck between the 
 third and little fin- 
 gers, Fig. 31, and the 
 stopper between the 
 first finger and thumb 
 of the same hand; af- 
 ter removing the 
 stopper, place the 
 quill between the nibs 
 of the pen, and fill as desired. If too much ink is placed 
 in the pen ragged lines and perhaps serious blots will be 
 suit. 
 
 Fig. 31 
 
USE OF INSTRUMENTS. 
 
 51 
 
 PROTRACTOR 
 
 (30) The protractor in most general use is a semi- 
 circle of celluloid, horn or metal whose circumference is 
 divided into degrees and perhaps half degrees. On the 
 
 Fig. 32 
 
 Line-0-Graph, Fig. 32, is shown a 90 protractor which 
 without any handicap can be substituted for the usual 
 180 instrument. To measure any desired angle, the 
 center of the circle is placed at the vertex, and on one 
 side of the given angle. The value of the angle may 
 then be read directly from the quadrant. 
 
52 MECHANICAL DRAFTING. 
 
 CHAPTER 3 
 
 ORTHOGRAPHIC PROJECTION 
 
 (31) Definition. An orthographic projection of any 
 object is such a representation on a given plane (usually 
 vertical or horizontal) as will show in true proportion 
 the contours of the object as seen in a direction perpen- 
 dicular to the plane; i. e., as though viewed from an in- 
 finite distance, when all the lines of sight would be paral- 
 lel to each other and perpendicular to the plane of pro- 
 jection. 
 
 PRINCIPLES OF ORTHOGRAPHIC PROJECTION 
 
 (32) It is seen from Fig. 1, which is a representation 
 of a machine part that, tho the object is represented as 
 we are accustomed to see it, the picture gives us abso- 
 lutely no conception of the ratio 
 
 of the several parts of the object 
 to each other; i. e., tho the sides 
 of the square hole in the top may 
 appear to be equal to the thick- 
 ness of the object, one has no 
 means of knowing exactly what 
 
 the relation is ; hence, unless actual dimensions were given 
 for every detail of such a drawing, and these dimensions 
 could be depended upon to be absolutely accurate, one 
 would have no means of making, except approximately, 
 the object which the drawing represents. Hence, it will 
 be appreciated that in making drawings for the use of 
 
ORTHOGRAPHIC PROJECTION 
 
 workmen in shops, such an application of Descriptive 
 Geometry should be employed as will represent each line 
 of the object at least once, in its true mathematical ratio 
 to other lines; i.e., such a representation, that if no 
 dimensions were given, one could compare lines by means 
 of a scale or dividers and be certain of their exact ratio 
 to each other. This branch of Descriptive Geometry is 
 known as Orthographic or Proportional Measurement 
 Projection. 
 
 Orthographic projection. To obtain such a projec- 
 tion of the machine part represented in Fig. 1, let us im- 
 agine that we have suspended it 
 in space with the face containing 
 the square hole horizontal; then, 
 see Fig. 2, let us imagine that 
 four planes be drawn about this 
 machine part in the positions 
 shown, one, a horizontal plane, a 
 second a vertical plane parallel 
 to the face A, and two other 
 planes perpendicular to both the 
 vertical and horizontal planes 
 just drawn. 
 
 Fig. 2 
 
 Coordinate planes and coordi- 
 nate angles. The three planes just constructed about the 
 machine part in Fig. 2 are known in orthographic pro- 
 jection as coordinate planes and are named individually, 
 the Horizontal or H plane, Vertical or V plane, Profile or 
 End plane; see Fig. 3. The four dihedral angles formed 
 by the H and V planes are known as 1st, 2nd, 3rd, and 4th 
 and are numbered in the order shown. 
 
MECHANICAL DRAFTING. 
 
 Projections or orthographic representations. In ex- 
 plaining the method used in obtaining the orthographic 
 representations of the machine part, the corner A, Fig. 
 4, will be taken as typical of all significant points of 
 
 Fig. 8 
 
 the object. It is desired to represent this point on each 
 of the three coordinate planes, the second End plane be- 
 ing for the time eliminated. From point A are dropped 
 three perpendiculars, one to each of the coordinate 
 planes; the points in which these perpendiculars pierce 
 
ORTHOGRAPHIC PROJECTION 
 
 55 
 
 these coordinate planes are known as the projections of 
 point A, and are called, V or Vertical projection or 
 Front View (always lettered a' if lettered at all), H or 
 Horizontal projection or Top View (always lettered a 
 if lettered at all), and Profile, End Projection, End or 
 Side View (always lettered a" if lettered at all) ; if then 
 from all of the points of the object perpendiculars were 
 dropped to the Vertical plane and lines drawn connecting 
 the piercing points of these perpendiculars in regular 
 
 FIRST ANGLE 
 PROJECTION 
 
 Fig. 4 
 
 order, Fig. 4, we would have on the Vertical plane a 
 drawing or projection representing perfectly the appear- 
 ance of the -front of the machine part ; a similar process 
 would give us on the Horizontal plane a correct repre- 
 sentation of the top of the object and on the End plane a 
 representation of the side of the object. 
 
 1st and 3rd angle projections. If the object be placed 
 in the 1st angle, as in Fig. 4, the projections referred to 
 above are known as first angle projections. If the object 
 
56 
 
 MECHANICAL DRAFTING. 
 
 is placed in the 3rd angle, as in Fig. 6, the projections 
 are known as third angle projections; i. e., the projections 
 of an object are known as First or Third Angle projec- 
 tions according to the angle in which the object is placed. 
 It should be noted that Figs. 4 and 6 show only those 
 
 / 
 
 / 
 
 / 
 
 V Plane 
 a' 
 
 Elevatio 
 
 
 
 ,- 
 
 a* 
 
 
 
 rr-n 
 
 I* 
 
 
 x 
 
 End View 
 P Plane Revolved 
 
 a 
 
 H Plane 
 
 
 x i 
 / i 
 
 L / 
 
 s 
 
 s 
 s 
 
 
 
 
 / 
 
 \~~ 
 \ 
 \ 
 
 \ 
 
 
 Plan 
 
 
 
 Re 
 
 olved ^ -^ 
 
 Fig. 5 
 
 parts of the coordinate planes that enclose the angle of 
 projection under consideration. No mention is made of 
 the Second or Fourth Angle projections because it would 
 be impracticable to use either as working drawings. 
 
 Revolution of coordinate planes. Already an appar- 
 ent difficulty has arisen in the question of how to repre- 
 sent all of these projections, e.g., of point A, Fig. 4, on a 
 single sheet of paper when in fact the three projections, 
 a, a' and a", are found on three planes at right angles to 
 
ORTHOGRAPHIC PROJECTION 
 
 57 
 
 each other. The line of intersection of the Horizontal 
 and Vertical planes is known as the Ground Line or G L; 
 the intersection of the Vertical and End planes is G 1 L r 
 This difficulty can now be solved as follows : Using G L 
 as an axis, Fig. 5, let us imagine that the portion of the 
 H plane in front of V is revolved down until it coincides 
 with the V plane. It should be remembered that the por- 
 tion of the H plane behind (not shown in the Fig.) re- 
 
 THIRD ANGLE 
 PROJECTION 
 
 volves up till it coincides with the V plane above G. L. In 
 this revolution, a revolves into the new position, a, on 
 the continuation of the perpendicular dropped, from a' 
 to G L; for, if thru the two lines Aa and Aa', Fig, 4, a 
 plane be passed, it will cut from the V plane a line 
 thru a' perpendicular to G L ; as a revolves about G L 
 down, it revolves in the plane a' Aa, and when it reaches 
 the V plane, must lie on the perpendicular to G L thru 
 a', the line cut from the V plane by the plane a' Aa. Since 
 a is before G L the distance Aa', a will be found below 
 G L the same distance ; a' is above G L the distance A a; 
 hence, the distance from G L to the points a and a' repre- 
 
58 
 
 MECHANICAL DRAFTING. 
 
 sents the exact distances which the point, of which these 
 are the projections, is from the V and H planes. If then, 
 G t L! be used as an axis and the portion of the Profile 
 plane in front of V be revolved to the right, a" comes 
 into the new position a", a distance to the right of Gi 1 Lj 
 equal to Aa' and a distance above Gr L equal to Aa, or on 
 the horizontal line thru a'. 
 
 Projections of objects. Advancing from the point A 
 just discussed, to all other elemental points of the object 
 and projecting them in turn in the same manner as was A, 
 
 H Plane Revolved 
 
 ITT"T 
 
 -71 
 
 /\ 
 
 P Plane Revolved 
 
 End Vie 
 
 o 
 
 Fig. 7 
 
 we find the representation of the machine part in the 
 first angle, when the several points are properly joined by 
 lines, to be as shown in Fig. 5. Proceeding in the same 
 manner with the object in the third angle we obtain the 
 views as shown in Figs. 6 and 7. It should be noted that 
 
ORTHOGRAPHIC PROJECTION 
 
 59 
 
 |_ _i 1 _| 
 
 r r ri 
 
 Fig. 8 
 
 the views are identical in character but appear in differ- 
 ent positions in respect to each other. In practice it is 
 the universal custom to omit 
 both ground lines together 
 with the boundary lines 
 of the three planes. The 
 resulting projections of 
 the object appear as in 
 Fig. 8. 
 
 Elimination of the first 
 angle. From Fig. 1, it is 
 noted that as we ordinarily 
 see objects the top appears 
 
 above the front and the right end to the right of the 
 front or the left end to the left of the front, according to 
 the position from which the object is seen. When the 
 object is placed in the first angle and the projections 
 revolved into the positions shown in Fig. 5, it is seen 
 that the left end projection comes in a position to the 
 right of the front and that the top is under the front, 
 an arrangement, by no means natural. While, when the 
 object is placed in the third angle, Fig. 6, and projections 
 revolved as shown in Fig. 7, the views assume a group- 
 ing identical with their order on the object itself; i.e., 
 the right end to the right of the front, and the top above 
 the front. Merely for the sake of this natural arrange- 
 ment the third angle will be selected in preference to the 
 first in making working drawings; i. e., all working draw- 
 ings will be third aoagle orthographic projections. 
 
(50 MECHANICAL DRAFTING. 
 
 SUMMARY OF PRINCIPLES 
 
 (33) It may be well to summarize a number of prin- 
 ciples brought out in this discussion, likewise to mention 
 several violations of pure orthographic projection. The 
 top view, Fig. 8, represents the exact appearance, with 
 lines in true proportions, of the top of the object; the 
 front view represents the same of the front of the object, 
 and the side view the same of the side of the object. 
 
 The top and front views must be directly above and 
 below each other and the front and end views must be 
 on the same horizontal lines as shown in Fig. 7, if the 
 group is to represent the true orthographic projection 
 of the object; a violation of this renders the whole draw- 
 ing incorrect. 
 
 PERMISSIBLE VIOLATIONS 
 
 (34) In Fig. 5, it is shown that the portion of the 
 End or Profile plane in front of V is revolved to the right; 
 this of course means that the portion of the Profile plane 
 behind V revolves to the left; while, in Fig. 7, the portion 
 of the Profile plane behind V is represented as being re- 
 volved to the right. This revolution to* the right of the 
 portion of the Profile plane behind V is ortho graphically 
 incorrect; however, in the case of the third angle projec- 
 tions it is tolerated for the natural order of projections 
 which it produces. 
 
 PROJECTIONS OF HIDDEN LINES 
 
 (35) In Figs. 5 and 7 certain lines of the projections 
 are shown dotted lines. This is the custom always fol- 
 lowed for showing hidden or invisible lines. For ex- 
 ample in the projection on the V plane, the two dotted 
 
ORTHOGRAPHIC PROJECTION 
 
 61 
 
 lines show that the hole thru the object is invisible when 
 viewed in a direction perpendicular to the V plane. A 
 simple rule for determining the visibility of a line is to 
 always consider the H projection a view from the top 
 and the V projection a view from the front. This ap- 
 plies equally to first and third angle projection. The 
 
 Fig. 10 
 
 projection on the P plane is considered a view from the 
 corresponding side of the object, that is, looking perpen- 
 dicularly thru the P plane at the object. 
 
 AUXILIARY PLANES OF PROJECTION 
 
 (36) Frequently an object is so shaped that it can- 
 not be placed in an entirely simple position with respect 
 to the planes of projection. The face K on the corner 
 brace shown in Fig. 9 will not be shown in its true size 
 
62 
 
 MECHANICAL DRAFTING. 
 
 on either the H, V, or P planes when the object is placed 
 in its simplest position with respect to these planes. 
 
 Fig. 11 
 
 The use of a fourth plane, which is perpendicular to H 
 but parallel to face K, will give an additional view which 
 will show K in its true size. Fig. 10. 
 
 Fig. 11 shows the correct arrangement of the four 
 views of the object after the V, P, and auxiliary planes 
 have been revolved into the H plane. 
 
ORTHOGRAPHIC PROJECTION 
 
 63 
 
 POSITIONS OF THE THIRD AND FOURTH VIEWS 
 OF AN OBJECT 
 
 (37) In Fig. 12 is shown the correct arrangement, 
 orthographically, of the three views of an object-box. 
 However, occasions may arise in which it will be in- 
 
 r 
 
 
 
 
 
 
 Top | 
 
 
 **< 
 
 \ 
 
 
 
 
 ^ \ 
 
 1 
 
 Front 
 
 
 | Side 
 
 
 1 I 
 1 I 
 
 
 1 
 
 
 
 
 
 Fig. 12 
 
 convenient to place the side view directly opposite the 
 front; in this case we may imagine that the line of inter- 
 section of the end plane and the horizontal plane becomes 
 an axis about which the end plane is revolved, Fig. 13, 
 until it coincides with the horizontal plane. This entire 
 horizontal plane is then revolved about its line of inter- 
 section with V as an axis, until it coincides with V. The 
 side view will now be found opposite the top instead of 
 the front. If two side views are necessary to show the 
 construction they may be placed on either side of the 
 
MECHANICAL DRAFTING. 
 
 front view, Fig. 14, or on either side of the top vieiv, 
 Fig. 15. No other arrangement is permissible. 
 
 Top 
 
 Side 
 
 
 
 
 1 / 
 
 
 ' 
 
 / 
 
 
 / \ 
 
 Front 
 
 
 J 1 
 
 1 1 
 
 
 / 
 
 
 
 ~~ 
 
 Fig. 13 
 
 Pig. 14 
 
 In constructing a three view drawing it is best always 
 to construct the top and -front views from dimensions 
 and by projection; 
 then, to obtain the 
 side views from these 
 two, entirely by con- 
 struction and not by 
 the use of dimensions. 
 For the sake of con- 
 struction the two 
 ground lines, Fig. 12, 
 may be drawn in 
 lightly; however, they should be erased when no longer 
 needed. 
 
 | Left 
 
 f 
 
 1 
 1 
 
 1 A 
 
 v \ 
 
 \ 
 
 Side 
 
 1 
 1 
 1 
 
 Tp 
 
 Ril 
 
 ,-ht Side I s N 
 
 \ 
 
 \^ 
 
 fl 
 
 
 
 I 
 
 L 
 
 t 
 
 _/T~ 
 
 J 
 
 ^ 
 
 ! 
 
 ^ 
 
 / 
 
 
 / ! 
 
 
 i/ 
 
 \ 
 \ 
 
 X 
 
 1 
 
 7' 
 
 / 
 
 / 
 
 ! J__L 
 
 > / Front' 
 
 f 
 
 Fig. 15 
 
WORKING DRAWINGS. 
 
 65 
 
 CHAPTER 4 
 
 WOEKING DRAWINGS 
 
 WORKING DRAWING 
 
 (38) Definition. A working drawing of a piece of 
 machinery is such a group of correctly and completely 
 dimensioned orthographic views of that object as will 
 give all the information necessary in constructing a 
 duplicate of the same. Fig. 1. 
 
 Fig. 1 
 
 DETAIL DRAWING 
 
 (39) Definition. A detail drawing is a working 
 drawing of one piece of any machine. 
 
 A group of detail drawings of all of the parts of a 
 machine or any collection of parts is termed a set of 
 details. 
 
66 MECHANICAL DRAFTING. 
 
 ASSEMBLY DRAWING 
 
 (40) Definition. An assembly drawing of a machine 
 is a one, two or three view orthographic projection of a 
 machine completely assembled; i. e., all parts in their 
 proper working place. Figs. 2. 
 
 Uses. Assembly drawings have three important uses. 
 (1) As an index to a working drawing; i. e., an assembly 
 of a machine is ordinarily given with the set of detail 
 working drawings to explain the use of each of these de- 
 tails in the machine; (2) For purposes of advertisement 
 or magazine illustration; (3) As a construction guide in 
 assembling machines which may be sent out from shops 
 in sections. 
 
 Characteristics. Some characteristics which may be 
 noted of assembly drawings when used for any of the 
 above purposes are: (a) All dimensions are ordinarily 
 omitted; (b) The several views are elaborately sectioned 
 to explain clearly all inside constructions; (c) When 
 given with a set of details the assembly will ordinarily 
 occupy a fixed relative place on the sheet, i. e., the lower 
 left corner or whole left side if necessary. 
 
 DETAIL WORKING DRAWINGS 
 
 (41) Arrangement of set of details. In making a set 
 of details a certain order of arrangement should be fol- 
 lowed, both for appearances and ease in reading the draw- 
 ing. As mentioned under assembly drawings, the assem- 
 bly should occupy the left portion of the sheet. In gen- 
 eral, the arrangement of the details on the sheet should 
 be such as to suggest their direct relation in the machine 
 itself; i. e., such an arrangement as is suggested by the 
 relation of these parts in the assembly. It may not always 
 
WORKING DRAWINGS. 
 
 67 
 
 Fig. 2 
 
68 
 
 MECHANICAL DRAFTING. 
 
WORKING DRAWINGS. 
 
 G9 
 
70 
 
 MECHANICAL DRAFTING. 
 
WORKING DRAWINGS. 
 
 71 
 
 be possible to carry out this scheme 
 completely; however, in general it 
 will be found possible so to arrange 
 the main details. For further ex- 
 planation see Fig. 3. The assembly 
 is here shown to the left, followed 
 along the bottom of the sheet by the 
 main detail, the remaining details 
 being arranged about the sheet 
 properly with relation to each other 
 if not to the main details. Fig. 3a 
 shows an arrangement with the as- 
 sembly omitted. 
 
 Fig. 4 
 
 Fig. 5 
 
72 
 
 MECHANICAL DRAFTING. 
 
 Order of work in a set of details. In making a set of 
 details, e. g., of the bell crank, Fig. 4, the following order 
 
 Fig. 6 
 
 of work will be found to lend to the greatest speed: 
 (a) Make list of details to be drawn and number of views 
 required of each, (b) Select scale, (c) Draw on 
 pieces of scrap paper rectangles or rectangular figures 
 of the proper size to enclose the desired number of 
 views of each detail, (d) Cut out these rectangles 
 and arrange them on the sheet of drawing paper on 
 which the details are to be drawn, (e) After the 
 rectangles are arranged mark their positions, Fig. 5. 
 (f ) Divide the rectangles on the sheet of drawing paper 
 into smaller rectangles to contain the separate views of 
 each detail, Fig. 6. The rectangles mentioned in (e) 
 
WORKING DRAWINGS. 
 
 and (f) should, of course, be put in only lightly 
 may be erased when no longer needed. Fig. 7. 
 
 and 
 
 Fig. 7 
 
 Detail signature. Accompanying each detail draw- 
 , whether the detail drawing be by itself or one of a 
 set, should be given a characteristic signature containing 
 the following information: Name of the machine part, 
 material of which it is made, number of parts required, 
 and some arbitrary number for the pattern if the object 
 
 Valve Crank C. I. 
 
 Reqd. 1. 
 Pattern No. A-3. 
 
 is to. be cast. This information should be given in the 
 manner shown above. 
 
74 
 
 MECHANICAL DRAFTING. 
 
 The letter A in the pattern number refers to the sheet 
 A of the Details of the Corliss engine of which this valve 
 crank is a part ; the number A-3, indicates that the valve 
 crank is detail number 3 on sheet A. 
 
 ORDER OF PENCIL WORK 
 
 (42) The most rapid progress can be gained in the 
 pencil work of a working drawing by following the order 
 given in Fig. 8. 
 
 Caution. It is by no 
 means wise to attempt to fin- 
 ish one of several views be- 
 fore doing any work on the 
 others. Fewer mistakes will 
 be made and more rapid 
 progress gained by working 
 on all views at the same 
 time; i.e., when a line is 
 
 Fig. 8 
 
 placed on one view, its pro- 
 jections in the other views should be obtained before 
 proceeding with other lines. All views will thus be fin- 
 ished at practically the same time. When one projection 
 of a line is obtained from a given . dimension, the other 
 views of this same line should be obtained by the prin- 
 ciple of projection rather than by making use of the 
 scale a second time. This practise, tho it may permit a 
 mistake to remain undetected, has the advantage of pro- 
 ducing drawings which are true orthographic projections. 
 
WORKING DRAWINGS. 75 
 
 ORDER OF PENCIL WORK 
 
 1 Border Lines 
 
 2 Title Space 
 
 3_Selection of Scale 
 
 4 View Spaces 
 
 5 Center Lines 
 
 6 Outlines 
 
 7 Auxiliary and Dimension Lines, and Dimensions 
 
 8 Section Lines and Notes 
 
 DIMENSIONING 
 
 (43) In dimensioning the following rules or sugges- 
 tions should be observed : 
 
 (a) Dimensions should read from left to right or 
 up, and in the direction of the dimension line. Fig. 9. 
 
 (b) The auxiliary lines used in dimensioning should 
 not quite connect with the lines from which they lead. 
 Fig. 10. 
 
 (c) Series. A series of dimensions should be given 
 on one continuous dimension line, as in Fig. 11, and not 
 as in Fig. 12. 
 
 (d) An overall dimension should always accompany 
 a series, both as a check and for the convenience of the 
 workman. Fig. 11. 
 
 (e) Diameters. Diameters should be placed on a 
 linear diameter of the circle as in Fig. 13 whenever 
 possible; when necessary to indicate the diameter on a 
 straight line projection of a circle, the dimension should 
 be accompanied by the letter D. 
 
 (f) Radii of arcs should be marked E. Fig. 14. 
 
76 
 
 MECHANICAL DRAFTING. 
 
 Incorrect 
 
 Fig. 15 
 
WORKING DRAWINGS. 77 
 
 (g) Inasmuch as the meaning of hidden lines is not 
 always clear, it is bad practice to place dimensions on 
 such lines. 
 
 (h) Place dimensions between views unless clear- 
 ness will be gained by placing them otherwise. 
 
 (i) Do not repeat dimensions on adjacent views. 
 
 (j) Dimensions should not be crowded. 
 
 (k) Dimensions always indicate the size of the fin- 
 ished object. 
 
 (1) Do not place dimensions on or along Center 
 Lines. Fig. 15. 
 
 (m) In general dimension from the center lines and 
 not from the outlines of the object. 
 
 (n) Fractions should be made with a dividing line 
 in the same line with, but not a part of the dimension 
 line. Fig. 11. 
 
 (o) The arrows of dimension lines contain two 
 barbs, while those of leaders, Figs. 13 and 16, but one. 
 
 (p) Arrows should be so placed that there may be no 
 confusion as to which line they point to. 
 
 (q) Leaders. All leaders, Fig. 16, should be made 
 mechanically and not freehand. 
 
 (r) Notes. For explanatory notes the leader should 
 end so that the notes may read either horizontally or 
 vertically as the dimensions, but not diagonally. Fig. 16. 
 
 (s) Dimensions up to two feet should be stated in 
 inches ; e. g.,' 12", 18", etc. 
 
 Two feet may be written either as 24" or 2'-0". 
 
 Except for sheet metal, dimensions above two feet 
 should be expressed as follows : 2'-3", 6'-4", 7'-0", etc. 
 
 The dimensions for sheet metal should be given in 
 inches and in the order of thickness, width, length; 
 e. g., i/ 8 x 36 x 120". 
 
78 
 
 MECHANICAL DRAFTING. 
 
WORKING DRAWINGS. 79 
 
 SECTIONING 
 
 (44) The primary function of orthographic projec- 
 tion is, of course, to represent the portions of an object 
 visible to the eye. Any constructions hidden by the sur- 
 faces in view may be represented by conventional lines 
 known as hidden lines, Fig. 17. The dotted lines in this 
 figure represent the three recesses in the top, front, and 
 side of the cube. It may be satisfactory to represent in 
 this way the interior construction of so simple an affair 
 as the object shown ; however, if the interior construction 
 is in the least elaborate this method is by no means satis- 
 factory. If an interior construction be represented by a 
 number of hidden lines which cross each other, the draw- 
 ing becomes so vague as to be almost unintelligible. For 
 this reason a substitute method has been devised for 
 showing any interior or hidden construction. According 
 to this method it may at any time be imagined that a 
 cutting plane, parallel to one of the coordinate planes, 
 can be drawn in any position, cutting away such portions 
 of the object as will expose any oilier parts one may ivish 
 to see. Ordinarily these planes will be found to pass thru 
 some axial line of the object, Fig. 18; however, if desired, 
 they may be imagined drawn elsewhere, Fig. 19. This 
 process of sectioning is purely imaginary and may be 
 represented on only one view of a two or three view 
 working drawing, the other views representing the ob- 
 ject unsectioned by any such plane. The process of sec- 
 tioning is strictly utilitarian ; i.e., one should section only 
 objects whose construction can be more clearly explained 
 by this process than otherwise. 
 
 Certain terms applying to sections are sometimes 
 confused from the fact that they may apply either to the 
 
80 
 
 MECHANICAL DRAFTING. 
 
 drawing or the object. These terms are quarter section, 
 half section, and full section. The confusion ordinarily 
 comes between the terms quarter and half section. From 
 Fig. 20, it is seen that when one-quarter of the object is 
 removed one-half of the drawing will be found sectioned. 
 Likewise if the entire front or 
 half of the object were removed 
 the drawing would be full sec- 
 tioned. Hence the term quarter 
 section will then, of course, be 
 entirely discarded, as it can refer 
 only to the object. 
 
 Solid cylinders. The drafts- 
 man should keep in mind the fact 
 that there is but one thing to be 
 gained in sectioning, i. e., to show 
 more clearly the interior construc- 
 tion of any piece of machinery; 
 if the section does not accomplish 
 this purpose it is just so much 
 wasted labor. This point refers 
 particularly to solid cylinders, 
 e. g., shafts, Fig. 21, bolts, screws, 
 etc., which should never be sec- 
 tioned. 
 
 Fig. 21 
 
 Interpolated or Revolved Sections. In such cases 
 as are shown in Fig. 22, with respect to rims and spokes 
 of wheels, standard construction iron, etc., sections known 
 as interpolated or revolved sections are given to show 
 the cross-section of the material at certain places. These 
 sections are obtained by passing planes perpendicular 
 
WORKING DRAWINGS. 
 
 81 
 
 to the axis of the piece to be sectioned and revolving 
 this plane 90 about the center line of the section thus cut. 
 
 Fig. 22 
 
 Section thru spokes. Whenever the cutting plane 
 passes thru spokes of wheels as is the case shown in 
 Fig. 22, the cross hatching is put in as if the plane had 
 been passed on the line AB. 
 
 Section lines. Indication of material by variation in 
 section lines. It is the custom in many shops to indicate 
 the material of which a piece of machinery is to be made 
 by using a characteristic section line for any parts of 
 that piece which have been sectioned, Fig. 23. There 
 are some apparent disadvantages in this, however, for 
 there is at present no universal standard system of sec- 
 tion lining. Some shops use one characteristic for brass, 
 wrought iron, etc., and others a radically different char- 
 acteristic. Furthermore, unless one uses these section 
 
82 
 
 MECHANICAL DRAFTING. 
 
 lines constantly or has a chart of them with him always, 
 he may find it quite 
 difficult to remem- 
 ber some of them. 
 A third objection 
 is that it requires 
 an excessive 
 amount of time to 
 draw some of these Fig - 23 
 
 section lines. 
 
 Indication of materials by abbreviations and univer- 
 sal section lines. For greatest convenience and ease, 
 both in making and reading a drawing, the writers 
 approve the universal section lining with material abbre- 
 viations as a sub- 
 stitute for the 
 above system, i. e., 
 the use of the 
 standard section 
 line now used for 
 cast iron as the 
 standard for all 
 materials and the 
 particular material 
 of which the piece 
 is to be made indi- 
 cated by its char- 
 acteristic abbrevia- 
 tion as shown in 
 Fig. 24. These ab- 
 breviations are 
 
 easy to remember and the section lines can be drawn 
 rapidly. 
 
 Where necessary a variation in space 
 between section lines may be substituted 
 for a change in direction of lines 
 
 Fig. 24 
 
WORKING DRAWING. 
 
 83 
 
 TRACING 
 
 (45) Tracing cloth is a fine quality of cotton coated 
 with a preparation which gives it a smooth hard surface 
 and renders it transparent. Of the various grades of 
 cloth on the market, the imported brand " Imperial M 
 gives by far the greatest satisfaction and is recom- 
 mended for general use. Always before making use of 
 any piece of cloth be sure to rip off about %" of the 
 selvage edge; it may prevent a bad buckling of the 
 tracing. 
 
 Tacking to the board. It is 
 
 best always to have the sheet 
 of tracing cloth slightly larger 
 than the sheet of paper so that 
 the tacks used in pinning down 
 the cloth may be placed outside 
 the sheet. In tacking down the 
 cloth, preferably with the dull 
 side up, be sure to stretch very 
 tight and tack firmly. See Fig. 
 25 for best order of tacking. 
 
 Preparation of the surface of the cloth. Unless pre- 
 pared in some way, the surface of the tracing cloth will 
 likely take the ink very poorly, giving ragged and faded 
 out lines. The cloth may be dusted or rubbed with chalk 
 or preferably magnesium carbonate, which may be pur- 
 chased at any drug store in 5-cent blocks, and then rubbed 
 with a piece of linen. 
 
 
 Board 
 
 
 
 ^^ Drawing 
 e 7 k 
 
 
 
 o - _ - ,- U4 .. _. k 
 
 
 
 ^Tracing Cloth 
 
 
 Fig. 25 
 
 Order of work. Unless one is sure of being able to 
 finish the tracing of several views of a drawing before it 
 
84 MECHANICAL DRAFTING. 
 
 is necessary to stop work, it will be found best always to 
 trace one view at a time, finishing that view before leav- 
 ing work. Tracing cloth has a decided tendency to 
 stretch and warp, and it may be found most difficult to 
 make old lines check with new if the tracing has been left 
 standing for a day or more. 
 
 Erasing. In erasing, use the pencil eraser always in 
 preference to the ink eraser or knife. It may require 
 more time to erase a mistake; 
 however, the cloth will be 
 found in good condition after 
 such erasing ; while the ink era- 
 
 Scrape out 
 y'with Unify 
 
 ser or knife quite easily rough- Fig - 26 
 
 ens the surface and causes blots on application of new 
 ink. A knife may be used to advantage in scraping out 
 slight accidental extensions of lines, Fig. 26. 
 
 Caution. If necessary to rule across ink lines, be 
 sure to move the pen rapidly. If the pen is moving 
 slowly the ink will likely follow down the old ink line to 
 the T-square or triangle and cause a bad blot. 
 
 Weights of lines. The visible and hidden outlines are 
 the heaviest lines on the drawing and should be slightly 
 less than 1/32" in width. This weight may be obtained 
 by using a number 3 line on the adjustable graduated 
 detail pen. All other lines on the drawing, i.e., dimen- 
 sion, auxiliary, center, and section lines, should have a 
 weight of number one. Fig. 27. 
 
 Order of inking in tracing. In tracing^ the following 
 order should be observed for most rapid and accurate 
 work. 
 
WORKING DRAWINGS. 85 
 
 Visible Outline 
 
 Hidden Outlines 
 
 Dimension, Auxiliary and Section Lines 
 
 Center Lii 
 
 Fig. 27 
 
 Undercut Tracing Ruler 
 
 Fig. 28 
 
 1. Center lines. 
 
 2. Large circles and arcs. 
 
 3. Small circles and arcs with the bow pen. 
 
 4. Irregular curves with special curve. 
 
 5. Horizontal lines with the T-square. 
 
 6. Vertical lines with T-square and triangles. 
 
 7. Inclined lines in groups, e. g., 30, 45, and 60. 
 
 8. Other oblique lines. 
 
 9. Dimension and auxiliary lines. 
 
 10. Section lining, dimensions and notes. 
 
 BEVELLED AND RAISED TRACING RULES 
 
 (46) For tracing, the two rulers shown in Figs. 28 
 and 29 are indispensable. With the bevelled ruler, Fig. 
 28, it is possible to rule across inked lines without any 
 danger of blotting. The raised ruler of Fig. 29 saves an 
 
86 
 
 MECHANICAL DRAFTING. 
 
 6 inch section from 18 inch beveled celluloid 
 ruler sold by Frederick Post Company. Screw 
 the point thru one-eight inch. Cut off on top 
 and file smooth. 
 
 Fig. 29 
 
 immense amount of time, as it makes it possible to con- 
 tinue tracing no matter how many ink lines are still wet. 
 
 CONVENTIONAL LINES 
 
 (47) The conventional lines shown in Fig. 27 are 
 standard and should be followed strictly. Concerning 
 the hidden lines, it may be said that no one thing except 
 dimensions will add to or detract from the appearance of 
 a drawing more than care or lack of it in the correct draw- 
 ing of hidden lines, both as to the uniform length of the 
 dashes and uniform space between dashes. In tracing, 
 follow strictly the weights given in the figure for these 
 various conventional lines. 
 
 SCALES 
 
 (48) Architect's scale. The spaces representing 
 feet on the architect's scale are divided into twelve equal 
 parts, making it possible to draw, without any interpo- 
 
WORKING DRAWINGS. 87 
 
 lation, plans, etc., of objects whose dimensions are given 
 in feet and inches. 
 
 Engineer's scale. On the engineer's scale the indies 
 are divided into various numbers of subdivisions, these 
 numbers being multiples of ten; i. e., the inches are 
 divided into 10, 20, 30, 40, 50, or 60 divisions. By use of 
 this scale without any interpolation maps may be made 
 and drawings plotted directly from field notes in which 
 the distances are all given in feet and tenths of feet. 
 
 Mechanical engineer's scale. Recently a scale has 
 been placed on the market on which the spaces repre- 
 senting inches have been divided into halves, quarters, 
 eighths, sixteenths, etc. Likewise a scale that combines 
 all of the three scales just described. Mechanical engi- 
 neers will find it to their advantage to own one or both 
 of these. 
 
 Scale versus size. A drawing made to such a size 
 that one-half inch on the drawing equals one foot on the 
 object drawn, is said to be made to one-half scale. How- 
 ever, if the drawing be made so that one-half inch on the 
 drawing represents one inch on the object the drawing is 
 said to be made one-half size or to a scale of " to V. 
 
88 MECHANICAL DRAFTING. 
 
 CHAPTER 5 
 FASTENEES 
 
 (49) In every field of construction the builder finds 
 it necessary to hold the component parts of the whole 
 together by means of fasteners. Among the numerous 
 kinds and varied shapes of fasteners, several are of such 
 universal importance that the draftsman as well as the 
 mechanic must be entirely familiar with the method of 
 manufacture and manner of representing them on draw- 
 ings. 
 
 Among others, rivets, keys, bolts and screws are to be 
 specially noted. The several kinds of rivets with their 
 customary conventional representations will be found in 
 the appendix. Brief mention is made of the common 
 standard keys in Art. 59. The greater portion of this 
 chapter will be devoted in main to the most widely used 
 fasteners, Bolts and Screws. 
 
 THREADS 
 
 (50) The Helix. The helix is a mathematical curve 
 often wrongly termed the Spiral. It is generated by mov- 
 ing a point on any surface of revolution, around and 
 along the axis of revolution. The motion of the 
 point in both directions is generally uniform but may be 
 variable in either or both of its motions. Thus we may 
 have cylindrical, conical, spherical and many other forms 
 of helices. On Bolts and Screws the thread is almost 
 always a cylindrical helix. For special purposes the 
 
FASTENERS. 
 
 thread may be a conical helix. The threads on water 
 pipes and their connections are of this class. Fig. 1 
 shows the geometric method of constructing a cylindrical 
 helix, which form will always be 
 understood when the term Helix 
 is used. The distance (x) is 
 called the pitch of the helix and 
 may be assumed at will. In con- 
 structing the helix the pitch dis- 
 tance is divided into the same 
 number of axial divisions as is 
 the projected circle. 
 
 From a mathematical stand- 
 point, a thread is simply a helix 
 cut around and into a solid cone 
 or cylinder. 
 
 THREADS CLASSIFIED 
 
 (51) V and Square threads. 
 
 Threads may be divided into two 
 general types or groups, called V 
 threads or Square threads accord- 
 ing to the shape of the tool used 
 in cutting them. Each of these 
 groups may be further classified 
 as Single, Double, Triple threads, 
 
 etc. This latter classification depends upon the number 
 of separate threads that are turned on one bar of metal. 
 All threads are in general Single threads except in cases 
 where rapidity of motion is required without a corre- 
 sponding increase in coarseness of thread. Some ex- 
 
 Fig. 1 
 
90 
 
 MECHANICAL DRAFTING. 
 
 amples of the foregoing mentioned threads are shown 
 in Fig. 2. 
 
 Single 
 
 Double 
 
 V Threads. The V thread is the usual thread found 
 on bolts and screws. It derives its name from the re- 
 semblance of its profile to the letter V. There have been 
 devised numerous modifications of this thread intended 
 to make it stronger and more durable and in some in- 
 stances to fit special classes of work. Fig. 3 shows the 
 profiles of some of these modified V threads. Of these 
 
FASTENERS. 
 
 91 
 
 several types the U. S. Standard (Seller's) thread is the 
 most used in this country. Sizes and dimensions for this 
 class of threads will be found in the Appendix. 
 
 P/8 
 
 Sharp V 
 
 U. S. Standard 
 
 P/ 
 
 Buttress 
 
 Fig. 3 
 
 Whitworth D 
 
 Square threads. In cases where a thread is con- 
 stantly being drawn or loosed or where heavy loads are 
 
 B & S Worm Thread 
 
 Fig. 4 
 
 Knuckle 
 
 to be lifted, the square thread finds an important place 
 due to the reduced friction over the V thread. This 
 
92 MECHANICAL DRAFTING. 
 
 thread finds a further field of usefulness in transmitting 
 motion. As with the V thread, many modified forms 
 have been devised. Fig. 4 illustrates a few of these 
 forms. 
 
 DEFINITION OF THREAD TERMS 
 
 (52) Crest, Root. The sharp edge 
 of the thread is known as the crest; 
 the depression line as the root, Fig. 5. 
 The term crest or outside diameter 
 is used to denote the diameter of the 
 crest of the thread and is assumed 
 equal to the diameter of the bar. The 
 diameter of the bottom of the grooves 
 is known as the root diameter and is 
 approximately equal to the crest di- 
 ameter of the nut or the diameter of 
 tap drill. 
 
 Pitch. For bolts and screws of 
 various diameters the size of the 
 threads must vary, hence the number 
 of threads per linear inch must vary. For each size bolt 
 or screw there is a standard number of threads per linear 
 inch which is often improperly termed the pitch of the 
 thread. The distance B, shown in Fig. 5, denotes the 
 pitch of the thread on the bolt. It should always be 
 understood that when the term pitch is used the distance 
 between two adjacent threads is meant, whether the 
 thread is single, double, or triple. In the case of the latter 
 two threads the term lead is used to denote the distance 
 between crests on the same helix. 
 
FASTENERS. 
 
 93 
 
 CONVENTIONAL REPRESENTATION OF THREADS 
 
 (53) As noted above, the projections of threads on 
 planes parallel to the axis of the threads are curved lines. 
 
 As each thread requires two 
 helices for its complete projec- 
 tion root and crest, Fig. 2 
 standard conventions have been 
 evolved to represent the differ- 
 ent threads. On large threads 
 the curved lines are replaced 
 by straight lines; the projec- 
 tion of the thread remaining 
 otherwise the same. Examples 
 
 Single 
 
 Single 
 
 Double 
 
 Single 
 
 Double 
 
 Fig. 6 
 
 Fig. 7 
 
 of these conventions are shown in Fig. 6. 
 
 On threads one inch or less in diameter the profiles are 
 omitted altogether and the forms shown in Fig. 7, A, B 
 and C are used. In drawing these conventions care must 
 be used not to make the slope of the lines too great, one- 
 half the pitch being right. The spacing may be done by 
 eye but should conform in a relative way to the number of 
 threads on the several bolts or screws on a drawing. 
 
94 
 
 MECHANICAL DRAFTING. 
 
 Light pencil guide lines should be ruled limiting the 
 length of the short heavy lines which should be equal to 
 the root diameter of the thread. When threads are to 
 be shown as invisible lines, the convention as shown in 
 
 Tapped Holes Top Views 
 
 
 Tapped Holes Front Views 
 
 Tapped Hole in Section' 
 Fig. 8 
 
 A Fig. 8 is recommended. Altho possessing no appear- 
 ance of a thread it is easy to construct and is universally 
 understood by mechanics. Fig. 8 represents the conven- 
 tional way of showing threads in tapped holes, the largest 
 diameter being known as the diameter of the thread. 
 In some instances threads may be made left handed. 
 
FASTENERS. 
 
 95 
 
 Care should be taken to show such threads by the proper 
 slope of the lines. Also attention is directed to the 
 change in direction of slope for threads in sectioned parts. 
 These variations may be understood more fully by ref- 
 erence to Fig. 9. 
 
 Conventional Representation of Screw Threads 
 
 Left Hand 
 
 Left Hand 
 
 Right Hand 
 
 Fig. 9 
 
 Right Hand 
 
 BOLTS AND NUTS 
 
 (54) Bolts. There are three distinct classes of bolts 
 in use at the present time called carriage, machine, and 
 stud bolts. Each is made from a rod of iron, threaded 
 on one end to receive a nut, and, with the exception of the 
 stud bolt, having the other end shaped into some form of 
 head. 
 
 Carriage-Bolt 
 
 Fig. 10 
 
 Carriage bolts. A carriage bolt may be denned as 
 a bolt with an oval head; its shank is squared from 
 %" to %" under the head, the side of this square being a 
 
96 
 
 MECHANICAL DRAFTING. 
 
 little larger than the diameter of the bolt. This bolt is 
 used in woodwork and when drawn into a hole the square 
 under the head takes a grip in the wood and prevents 
 turning while the nut is drawn. The nut being thinner 
 than the ordinary nut the whole effect is to give a more 
 finished appearance to this class of work, especially after 
 painting. Fig. 10 is given to further explain this class 
 of bolts. 
 
 Root 
 Crest 
 
 m 
 
 ^ 
 ^ \ 
 
 ^^ 
 
 
 \ 
 P 
 
 k 
 
 V 
 
 
 
 
 
 - A- 
 
 ~ 
 
 
 N 
 
 ^v- 
 
 7 
 
 * 
 
 Fig. 11 
 
 Machine bolts. Machine bolts are divided into a 
 number of classes, each class being named either from 
 its peculiar shape or its distinctive use. The dimensions 
 
FASTENERS. 97 
 
 of the several parts of all such bolts have been standard- 
 ized, tables arranged, and the construction and size of 
 every part of any particular size bolt is perfectly definite. 
 
 Hexagonal and square-headed bolts. Inasmuch as 
 these two classes of bolts are usually dealt with in the 
 same table of dimensions, it will perhaps be as well to 
 include both in this discussion. In Fig. 11 is shown 
 the conventional manner of representing hexagonal and 
 square-head bolts in a mechanical drawing. It will be 
 noticed that the hexagonal bolt is so placed that three 
 faces of both the bolt head and the nut are visible and 
 the square head bolt is so placed that two of its faces are 
 visible. This placing should be strictly adhered to, espe- 
 cially in machine sketching where it may be necessary to 
 show the kind of bolt by only one view. 
 
 Likewise it will be seen that on both bolts the outer 
 corners of the heads and nuts have been ground or turned 
 off until the face of the head and nut is a circle tangent 
 to the hexagonal or square limits of the head or nut. 
 This bevel on the head or nut is called the chamfer of 
 the head, etc. 
 
 In constructing the end view of any bolt the chamfer 
 circle is first drawn (the diameter of this chamfer circle 
 will be found in table under head of "Distances Across 
 Flats" or "Short Diameter") and the hexagon or square 
 circumscribed by means of the 30x60 or 45 triangles. 
 No other method should be used for obtaining the hex- 
 agon or square. 
 
 The geometric construction of these bolts should be 
 entirely familiar to the draftsman, and Fig. 11 should be 
 thoroly studied and mastered in every detail. Fig. 12 
 should also be consulted in this connection. 
 
98 
 
 MECHANICAL DRAFTING. 
 
 Hex. Hd. Bolt 
 
 Oval Fillister Hd. Mach. Screw 
 
 Plat Fillister Hd. Mach. Screw 
 
 s| -; Set Screws 
 
 Headless Low Head 
 
 II 
 
 Set Screw Points 
 
 Flat Conical Oval Dog 
 
 Fig. 12 
 
FASTENERS. 
 
 99 
 
 Stud bolt. On account of the particular use and form 
 of the stud bolt it deserves special mention. It has no 
 head and is threaded on both ends nearly up to its center. 
 In places where a headed bolt is impracticable the stud 
 bolt is screwed into the tapped hole in the piece of metal ; 
 the part to be clamped in 
 place is then slipped on 
 the projecting end and "an 
 ordinary nut used to draw 
 the piece tight. The bolt 
 thus serves the second 
 purpose of being a guide 
 in assembling which makes 
 it almost indispensable in 
 places where machine 
 parts are removed and re- 
 placed very often. Fig. 
 13 illustrates this impor- 
 tant bolt. 
 
 Fig. 13 
 
 Nuts. A carriage or machine bolt nut may be defined 
 as a square or hexagon of steel or wrought iron of any 
 desired thickness with a threaded hole thru the center. 
 They need no classification, since they differ only in 
 shape, thickness and finish. They may be square or 
 hexagonal, very thick or quite thin, and if rough they 
 quite likely have been punched from sheets of wrought 
 iron or steel, while the finished nuts have been cut from 
 square or hexagonal bars of steel, Fig. 11. 
 
 DIMENSIONING BOLTS 
 
 (55) Length, diameter. The length of a bolt is 
 always understood to be the distance from the end to 
 
100 MECHANICAL DRAFTING. 
 
 the under surface of the head. In placing a note on a 
 drawing designating the size of bolt used, the diameter, 
 length, and pitch of thread should be given in the order 
 named, followed by the kind of bolt wanted; e.g., 
 l"x 4"x 8 thrds. per in. Fin. Hex. Bolt. If the bolt is to 
 be a U. S. Std. bolt, only the length and diameter are 
 needed. On large or long bolts the threaded length 
 should be given. 
 
 SCREWS 
 
 (56) Definition. A screw may be denned as a rod 
 of iron or steel threaded on one end and containing a 
 square, hexagonal, or slotted head on the other by which 
 the screw is turned. Screws are divided into four gen- 
 
 o 
 
 Lag Screw Allen Headless Set Screw 
 
 Wood Sere 
 
 ShouJder. Screw 
 
 Drive Screw 
 
 Fig. 14 
 
 eral classes wood, set, cap, and machine screws. Figs. 
 12 and 14 illustrate some of the types most commonly 
 used. Tables of dimensions may be found in the Appen- 
 dix. 
 
 In listing screws on a drawing the method outlined 
 in Art. 55 for bolts should be followed. 
 
FASTENERS. 
 
 PIPE THREADS 
 
 101 
 
 (57) Many times the engineer is required to deal 
 with plans in which water, steam or gas pipes are used. 
 In order to make 
 all connections wa- 
 ter or steam-tight 
 the threads are 
 turned with a 
 standard taper of 
 1" to 16". Care 
 
 should be taken to specify this kind of thread when 
 used on a drawing and to designate its size by giving 
 the inside diameter of the pipe and not the outside diam- 
 eter as is done on bolts and screws. Fig. 15 further illus- 
 
 Complete Threads Imperfect Threads 
 
 Starter or Taper Tap 
 
 Medium or Plug 
 
 Finishing or Bottoming 
 
 Fig. 16 
 
 trates this type of thread. Tables of pipe sizes and 
 threads will be found in the Appendix. 
 
102 
 
 MECHANICAL DRAFTING. 
 
 IHV SHOP OPERATIONS 
 
 (58) Taps and Dies. The usual method of cutting V 
 threads is by means of tools known as taps and dies. 
 Figs. 16 and 17 furnish general information concerning 
 these shop tools. The tap is used for cutting the threads 
 
 Dies. 
 
 Fig. 17 
 
 m nuts and also for threading holes drilled in parts of 
 machines. Dies are used for threading bolts and screws 
 and other rods of iron not greater than V in diameter. 
 
FASTENERS. 
 
 103 
 
 Fig. 20 
 
 Woodruff Key 
 
104 
 
 MECHANICAL DRAFTING. 
 
 Square threads, threads not having a standard pitch, 
 and all large threads are turned on the lathe. 
 
 KEYS AND KEYWAYS 
 
 (59) In fastening wheels, pulleys, etc., to shafts two 
 classes of fasteners may be used, set-screws or keys. 
 Set-screws may be used to advantage in all cases in which 
 the twisting force on the shaft is 
 very small. It is not wise to use 
 such a fastener on large pulleys 
 or in cases in which the load is 
 likely to be very great. In this 
 latter case one of three varieties 
 of key may be used according to 
 the nature of the machine. These 
 keys and keyways are (a) Keys 
 on flats, Fig. 18; (b) Straight 
 seated keys, Fig. 19; (c) Wood- 
 ruff keys, Fig. 20; (d) Round keys, Fig. 21. It is clearly 
 seen that the first type of key has a very limited use, and 
 owing to the fact that the Woodruff key is patented, the 
 straight keys and seats have the most general use. In 
 this type of key, it is seen, Fig. 19, that one-half of the 
 recess is milled or cut into the shaft (this groove being 
 known as a keyseat) while the other half of the recess is 
 cut into the hub of the pulley and is known as the keyway. 
 When fitted over each other they should form nearly a 
 square, the height being slightly less than the width. The 
 keys used in this connection are cut from square bars of 
 cold rolled steel and filed to a slight taper on one side 
 only, so that when driven in far enough they wedge 
 
 Fig. 21 
 
FASTENERS. 105 
 
 between the hub and shaft, thereby preventing the pulley 
 both from sliding along the shaft in either direction and 
 from turning about the shaft. 
 
105 MECHANICAL DRAFTING. 
 
 CHAPTER 6 
 
 SHOP TERMS, TOOLS, MACHINES 
 Draftsman's Use of Shop Terms. 
 
 (60) Certain terms that are in common use in the 
 workshop are used by the designer and draftsman in the 
 form of a direction to the workman. Such words as 
 "drill," "tap," "ream," "finish," etc., are shop terms 
 directing the workman to perform the operation indi- 
 cated. When these words are used on a drawing, the 
 lettering should be so placed that there will be no con- 
 fusion in determining to exactly what part of the ob- 
 ject the term applies. Leaders should point to the part 
 referred to if the meaning is not clear without them. If 
 additional wording other than the simple term is needed, 
 the English language should be used in such a way that 
 the meaning of the note cannot be misunderstood. 
 
 Ordinarily, working drawings sent to the shop are 
 made so complete that the same drawing will answer for 
 the pattern-maker, blacksmith, and machinist. In this 
 case, each workman uses only that part of the information 
 on the drawing that applies to his work. Some large 
 shops follow the method of making a separate drawing 
 for each of these workmen, so that he will be supplied 
 only with the dimensions and notes that apply to his par- 
 ticular work. 
 
 FINISH 
 
 (61) A casting or forging is in a rough state when it 
 comes from the foundry or forge shop and if certain parts 
 are to be machined, they are marked "finish" or simply 
 
SHOP TERMS, TOOLS, MACHINES. 
 
 107 
 
 "f" on the drawing. The most convenient way of indi- 
 cating that a surface is to be finished is to place the letter 
 "f" across the straight line projection of the surface. 
 In Fig. 1, the upper and lower faces of the block are to 
 
 Drill |" 
 
 OJ 
 
 ' 
 
 J ! 
 
 
 .1 
 
 i 
 
 i , 
 
 
 
 | 
 
 i 
 
 
 1 
 
 Fig. 1 
 
 be machined. Since the dimensions given on the draw- 
 ing indicate the size of the finished object, surfaces 
 marked with an "f" will indicate to the pattern-maker 
 or blacksmith that allowance for the tool cut must be 
 made on the casting or forging. 
 
 The note "f all over" placed under a detail drawing 
 means that the entire surface of this part is to be ma- 
 chined. 
 
 The operations coming under the head of "finish" will 
 in general be performed on lathes, planers, or shapers 
 such as are shown in accompanying cuts. 
 
108 
 
 MECHANICAL DRAFTING. 
 
 MILL 
 
 (62) In the shop operation required in cutting slots, 
 grooves known as key seats, also other similar opera- 
 tions, Fig. 2, a machine known as a milling machine 
 
 Cut on Milling Machine 
 
 Key Seat for 
 Woodruff Key 
 
 Slot 
 
 Fig. 2 
 
 is used. The cutting tools resemble the common type 
 of circular saw and operate on the same principle. As 
 seen on pages 109 and 110, which are horizontal milling 
 machines, the cutter is fastened rigidly to the revolving 
 shaft or arbor while the piece of material to be machined 
 is clamped to the table and the table moved, either by 
 hand or automatically, slowly under the cutter, as a log 
 is fed into the saw of a sawmill. For special work mill- 
 ing cutters of many odd designs are made, as seen on 
 pages 111 and 112. The machine shown on page 113 is 
 known as a vertical milling machine, the shaft or arbor in 
 this case being vertical. To prevent vibration in the 
 arbor of the horizontal machine (this vibration being 
 
SHOP TERMS, TOOLS, MACHINES. 
 
 109 
 
 HOKIZONTAL MILLING MACHINE 
 
110 
 
 MECHANICAL DRAFTING. 
 
 HORIZONTAL MILLING MACHINE 
 
SHOP TERMS, TOOLS, MACHINES. 
 
 Ill 
 
 MILLING CUTTERS 
 
112 
 
 MECHANICAL DRAFTING. 
 
 MILLING CUTTEKS 
 
SHOP TERMS, TOOLS, MACHINES. 
 
 113 
 
 VERTICAL MILLING MACHINE 
 
114 
 
 MECHANICAL DRAFTING. 
 
 known as chatter) and consequent rough work of the cut- 
 ter, chatter braces, shown below, are being put on most 
 machines of late design. The note used to indicate any 
 desired milling operation may be as follows: "2" mill"; 
 the two inches indicating the diameter of the milling 
 cutter; or "Mill %" key seat, 4" long," "Mill %" slot, 
 %" deep/' etc. 
 
 HORIZONTAL MILLING MACHINE WITH CHATTER BRACES 
 
 Since economy of time is a large item in shop work 
 the designer will do well to study carefully the many pos- 
 sibilities of the milling machine. Next to the lathe and 
 drill it is perhaps the most efficient machine in use. 
 
SHOP TERMS, TOOLS, MACHINES. 
 
 115 
 
 TWIST DRILLS 
 
116 
 
 MECHANICAL DRAFTING. 
 
 DEILL PRESS 
 
SHOP TERMS, TOOLS, MACHINES. 117 
 
 DRILL 
 
 (63) The term "drill" may be applied to all holes of 
 small diameter up to two inches, which do not need a high 
 finish. Holes which are to be tapped for screws or which 
 are to receive a bolt or which are later to be finished to 
 a larger diameter with a reamer may be cut on a drill 
 press with a twist drill. On pages 115 and 116 are 
 shown twist drills and drill presses of various designs 
 used in performing the shop operation termed "drill." 
 
 BORE 
 
 (64) In all cases where a round hole is to be 
 machined and the hole is either so large that a twist drill 
 cannot be used or it is desired to give such a finish to the 
 hole as is impossible in the inevitably somewhat rough 
 work of the twist drill, the work will be done on a lathe 
 by means of the short boring tools or by cutting tools in 
 connection with the boring bar and the operation will be 
 termed boring instead of drilling. The note referring to 
 such an operation is 1" bore, etc., the dimension referring 
 to the diameter of the hole. Such boring operations 
 are performed on a lathe or boring machine, pages 118 
 and 119, and are ordinarily necessary on holes whose 
 diameters are greater than two inches. Twist drills 
 larger than two inches in diameter are not in very com- 
 mon use as it requires an extremely heavy drill press to 
 operate them satisfactorily. 
 
 If a cylindrical part is to fit into a bored hole, the 
 terms "driving fit," "forced fit," "turning fit," etc., will 
 tell the kind of fit that is required. 
 
 The dimension given will indicate the size of the part 
 
MECHANICAL DRAFTING. 
 
 ri 
 
SHOP TERMS, TOOLS, MACHINES 
 
 119 
 
120 
 
 MECHANICAL DRAFTING. 
 
 REAMERS 
 
 EEAMEKS 
 
SHOP TERMS, TOOLS, MACHINES. 121 
 
 to be fitted into the hole and the necessary allowance 
 for the desired fit will be made in the boring operation. 
 
 BEAM 
 
 (65) Wherever a small hole is to be given a certain 
 taper or is to be given a finish not possible with a twist 
 drill or is to be cut to a very exact dimension, a tool 
 known as a reamer, page 120 should be used and the term 
 applying to such an operation is ream. This operation 
 of course presupposes that a hole slightly less in diam- 
 eter has already been cut with a twist drill, or bored on 
 a lathe. 
 
 CORE 
 
 (66) The term core is used in connection with cast- 
 ings only and indicates that the hole referred to is to 
 be produced by a core (a hardened cast of sand of the 
 desired shape and size), which is placed in the mold 
 when the casting is made. The pattern-maker must make 
 provision for the core in the construction of the wood 
 pattern of the casting. 
 
 11 Core 1%"" means that a core 1%" in diameter will 
 be used in the mold. The cored hole will of course be 
 as rough as the surface of a rough casting. 
 
 TAP 
 
 (67) The term tap applies to the shop operation 
 required in cutting V threrxds in holes of comparatively 
 small diameter ; that is, less than one and one-half inches. 
 The note used to indicate that a certain hole is to be 
 threaded to a certain pitch is as follows : y 2 " tap x 13 pi. 
 
122 
 
 MECHANICAL DRAFTING. 
 
 On pages 101 and 102 are shown a series of standard 
 taps and likewise both bolt and pipe dies used in cutting 
 V threads on bolts, pipes, etc. 
 
 TAP DRILL 
 
 (68) A tap drill is a twist drill of the common type, 
 named a tap drill in this case because it has been used 
 in drilling a hole which is to be threaded to receive a 
 screw. 
 
 HARDEN, TEMPER, ANNEAL 
 
 (69) These are terms which have to do with the heat 
 treatment of the machine parts in question and there- 
 fore will be interpreted by the workmen in the forge 
 shop. 
 
 FILLET 
 
 (70) It is a well recognized principle of mechanics 
 that a break is much more likely to occur in sharp 
 
 Killed Curium- 
 
 Fig. 4 
 
 corners of a machine than elsewhere, the corner seem- 
 ing to furnish a starting point for the break. For this 
 reason, and others which need not be mentioned, all 
 corners found on castings are seen to be slightly rounded. 
 
SHOP TERMS, TOOLS, MACHINES. 123 
 
 Fig. 3. This rounded corner is known as a fillet; like- 
 wise the material which is used to make this fillet in pat- 
 terns takes the same name. In Fig. 4 is shown the 
 method of making such filleted corners in patterns. The 
 triangular piece shown is made of wood, shaped by driv- 
 
 Steel Die %" Rouml 
 
 Cold Rolled Steel 
 Hole the 
 
 Shape of the Fillet 
 Fig. 5 Fig. 6 
 
 ing thru a Die, Fig. 5, as dowel pins, or of hard wax 
 rounded by a heated rod, Fig. 6, or it may be of leather 
 which can be purchased in coils of any length. The 
 leather fillets, of course, are most convenient for very 
 irregularly shaped pieces. The radius of the arc of such 
 fillets is quite generally %" ; however, it is necessarily a 
 matter of machine design and for very large pieces the 
 radius must be greater than 14". 
 
 BEARINGS 
 
 (71) Brasses. In certain types of machines it is 
 desirable to use brass for bearings rather than the com- 
 bination of lead and zinc and copper. Such bearings are 
 ordinarily made in halves, constructed so as to permit 
 of a slight adjustment, Fig. 7. These half bearings are 
 commonly known as brasses. 
 
 Babbit. The alloy of lead, zinc and copper mentioned 
 above is commonly known as babbit. The greater the 
 amount of zinc and copper, the harder this compound is. 
 Two of the material advantages of babbit for bearings 
 
124 
 
 MECHANICAL DRAFTING. 
 
 are, that the metal is cheap, and such bearings can be 
 easily replaced by a workman of but ordinary experience. 
 Babbit lining is poured while molten into the cast iron 
 casings with the shaft in place. 
 
 Brass Box 
 or Brasses 
 
 Fig. 7 
 
ISOMETRIC AND OBLIQUE PROJECTION. 125 
 
 CHAPTER 7 
 
 ISOMETRIC AND OBLIQUE PROJECTION 
 
 EXPLANATION OF PRINCIPLES 
 
 (72) If through a given point called the origin three 
 lines be drawn at right angles to each other, as the three 
 adjacent edges of a cube, we have the usual mathemat- 
 ical coordinate axes X, Y, and Z. These axes taken in 
 pairs determine three planes, such as the three coordi- 
 nate planes used in Chapter 3. If now an object with 
 rectangular or square faces, for example a cube, be placed 
 in the first angle, and be viewed in turn in the direction 
 of the axes X, Y, and Z, the figure in each case will appear 
 to be simply a square. These squares projected on their 
 respective coordinate planes give, of course, the ortho- 
 graphic projections of the cube, and it should be remem- 
 bered that the square seen, if the cube is viewed in the 
 direction of the X axis, represents the entire object and 
 not merely the face of it. Thus we see that one face 
 only is visible, in general, in each view. 
 
 If now we imagine a line drawn in such a direction 
 as to make equal angles with X, Y, and Z, for example, 
 the diagonal of the cube, and view the object in the direc- 
 tion of this line, it is apparent that three faces will be 
 visible, although now none shows as a rectangle, nor do 
 we see any of the edges in their true lengths. However, 
 all the edges of the cube parallel to axes X, Y, and Z 
 are equally or proportionally fore-shortened if seen in 
 the direction of this new axis, known as the isometric 
 axis. The plane perpendicular to the isometric axis is 
 
126 
 
 MECHANICAL DRAFTING. 
 
 known as the isometric plane, and the projection on this 
 plane of any object viewed in the direction of the iso- 
 metric axis is known as an isometric projection. The 
 sheet of paper or blackboard may, of course, be conceived 
 as the isometric plane, on which the projections of the 
 three axes X, Y, and Z will be right lines making 120 
 degrees with each other and the projection of the iso- 
 metric axis will be their point of intersection, Fig. 1. 
 This point of intersection may also be termed the origin. 
 
 Fig. 1 
 
 Fig. 2 
 
 Fig. 3 
 
 DIRECTRICES 
 
 (73) The orthographic projections on the isometric 
 plane of the three coordinate axes X, Y, and Z are known 
 in the drawing as the directrices, and occasionally as the 
 isometric axes. Since the coordinate axes make with each 
 other equal angles, their projections (the directrices) 
 also make equal angles (120 degrees) with each other. 
 This being true, when it is desired to make any isometric 
 projection, the directrices may be drawn immediately 
 through any chosen point and at 120 degrees to each 
 other. One of the directrices is usually taken vertical, 
 Fig. 1 ; however, the arrangements shown in Figs. 2 and 
 3 are frequently used. 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 127 
 
 ISOMETRIC SCALE 
 
 (74) Since the coordinate axes are oblique to the 
 isometric plane, their projections are shorter than the 
 axes themselves. However, since each axis makes the 
 same angle with the isometric plane, one inch measured 
 on each of the three axes will project in equal lengths 
 on tho isometric plane. For all ordinary purposes, in 
 
 Origin 
 
 Fig. 4 
 
 making an isometric projection, it is more convenient to 
 lay off the projections of lines which are parallel to 
 X, Y, and Z equal in length to the actual lines. It is 
 seen, of course, that the projection made with such 
 measurements represents the object as being about fifty 
 per cent larger than it actually is. Since the direct use 
 of the scale in measuring these lines full length makes 
 so much for convenience and only enlarges the view, this 
 procedure is usually followed. If, on the other hand, 
 it is desired that the projection be mathematically cor- 
 rect, the projection of all lines parallel to X, Y, and Z 
 must be measured according to the isometric scale. Since 
 each coordinate axis makes with the isometric plane an 
 
128 
 
 MECHANICAL DRAFTING. 
 
 angle of 35 16', if we assume the hypotenuse AB of the 
 right triangle, Fig. 4, to be one of the coordinate axes, 
 BC the isometric axis, and CA the isometric plane, viewed 
 edgewise, the isometric projection of any given length 
 BE on the axis BA would project on the plane with a 
 
 Isometric Scale 
 
 Pig. 5 
 
 length equal to Ce. Figs. 5 and 6 illustrate simple 
 methods for obtaining the isometric scale. 
 
 (75) Problem 1. To construct the isometric projec- 
 tion of any parallelepiped. 
 
 Construction. Cube 2" on edge, Fig. 7. 
 
 Thru point are drawn the axes OB, OA, and OC. 
 making with each other angles of 120 
 degrees. From 0, along OA, measure 
 with the isometric scale 2"; the same 
 along 00 and OB to points D, E, and 
 F. OD and OE then represent the 
 two adjacent sides of the base, and 
 lines from D and E parallel to OE and 
 OD complete the base. In similar 
 manner the vertical faces DOF and Fig - 7 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 129 
 
 FOE are completed; then draw the top base FS and 
 finally the faces SD and SE. 
 
 IRREGULAR OBJECTS 
 
 (76) Inasmuch as all but a very small percentage of 
 machine parts are either of rectangular shape or can 
 easily be enclosed in such 
 a box or parallelepiped, 
 the isometric projections 
 of irregular objects are 
 easily constructed with the 
 aid of such an enclosing 
 parallelepiped, Fig. 8. In 
 most cases it will be found 
 necessary to section the 
 object in order to show 
 the interior portion or 
 cross-section, Figs. 9 and 
 10. 
 
 Fig. 8 
 
 CIRCLES 
 
 (77) Problem 2. To construct the isometric projec- 
 tion of a circle, Fig. 11. 
 
 8 point method. ABCD is the isometric projection of 
 a square in which a circle is inscribed. On edge AB con- 
 struct a square and inscribe in it a circle. Draw the hori- 
 zontal diameter of this circle and diagonals of the square. 
 The points of tangency of the circle with the square and 
 the 4 points of intersection with the diagonals constitute 
 the desired 8 points. If the diagonals of the parallel- 
 ogram be drawn the isometric projections of these 8 
 
130 
 
 MECHANICAL DRAFTING. 
 
 Fig. 10 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 131 
 
 points may be obtained as shown and the ellipse drawn 
 thru them by means of the irregular curve. 
 
 Fig. 11 
 
 Approximate mechanical method. The isometric 
 projection of a circle which lies in a plane parallel to 
 the plane of any two isometric axes will always be an 
 ellipse inscribed in a rhombus ABCD, whose acute angles 
 A and C are 60 degrees, and which itself is the isometric 
 projection of the square circumscribing the circle repre- 
 sented. The ellipse may be approximated with satisfac- 
 tory exactness if made of arcs of circles as illustrated in 
 Fig. 12. From the obtuse angles 
 B and D perpendiculars are 
 dropped to the opposite sides. 
 Then with radius E equal to DE 
 and centers B and D the arcs HF 
 and GE are described; with cen- 
 ters K and L, and radius r equal 
 to LE, the small circles are de- 
 scribed completing the approxi- 
 mate ellipse. Fig. 12 
 
132 
 
 MECHANICAL DRAFTING. 
 
 DIMENSIONING 
 
 (78) In placing dimensions on an isometric drawing, 
 the same rule must be followed as in orthographic work- 
 ing drawings ; the dimensions must read from left to right 
 or from the bottom up. In following this rule it will be 
 found always that the dimension lines are parallel to the 
 coordinate axes, never otherwise. In giving the diam- 
 
 eters of circles the method shown 
 in Fig. 13 is preferable to plac- 
 ing the diameter directly on the 
 isometric of the circle. On in- 
 spection of Fig. 14 it is seen that 
 there are actually three faces of 
 the object to be dimensioned and 
 in giving the dimensions for face 
 No. 1, which is parallel to the 
 isometric plane No. 1, it must first 
 be decided what directions consti- 
 tute from left to right and from bottom up. The same 
 thing must be decided for faces 2 and 3. In Fig. 15 is 
 given a key \\hich will be useful in dimensioning. In con- 
 
 rig. 15 
 
ISOMETRIC AND OBLIQUE PROJECTION. 133 
 
 nection with this key it will be necessary for the student, 
 in placing dimensions, to decide merely to which face of 
 this key his dimensions are parallel, Figs. 9 and 10. 
 
 OBLIQUE PROJECTION 
 
 (79) Inasmuch as circles are so rarely found in such 
 positions that their projections are true circles in iso- 
 metric projection, a variety of projection has been de- 
 vised in which it is possible so to place circles that their 
 projections are circles and are easily drawn. This is 
 known as oblique projection. 
 
 In oblique projection as in the isometric projection 
 just discussed, we have one plane of projection. The line 
 of sight is always assumed oblique to the plane of projec- 
 tion. We may call this line the oblique axis. If two of the 
 coordinate axes are placed parallel to the plane of projec- 
 tion and projected thereon by lines parallel to the line of 
 sight, the projections will be unchanged in relation to 
 each other. In projection the third axis will, however, 
 be foreshortened and inclined to the other two at an angle 
 other than 90. This angle may be varied at will accord- 
 ing to the angle of inclination of the oblique axis with the 
 plane of projection, but is 
 usually assumed at 30, 45, 
 or 60 with the horizontal. 
 These projections of the 
 coordinate axes are called 
 the directrices. 
 
 DIRECTRICES AND CO-ORDINATE PLANES 
 
 (80) Thru the origin, 0, Fig. 16, (a) and (b), are 
 drawn three directrices as shown; one horizontal, a second 
 vertical, and the third to the right or left at 45, 30, or 
 
134 
 
 MECHANICAL DRAFTING. 
 
 60 with the horizontal, preferably 45. These three lines 
 represent lines at right angles to each other, and may be 
 compared to the three adjacent edges of a cube. 
 
 Taken two and two, these directrices include coordi- 
 nate planes as follows : OA and OB, plane 1, or the plane 
 of true circles; OB and OC, plane 2, a second vertical 
 plane, and OA and OC, plane 3, a horizontal plane. 
 
 DIMENSIONING 
 
 (81) In oblique as well as in isometric projection, 
 the problems of dimensioning are threefold ; i. e., any 
 object drawn may have faces parallel to each of the three 
 
 coordinate planes in Fig. 
 17. In placing dimensions 
 for constructions on these 
 faces it is necessary, of 
 course, to decide what di- 
 
 Fig. 18 
 
 rections constitute from left to right and from bottom up. 
 The key in Fig. 18 may be used in a manner similar to 
 that of the key given for isometric projection. Inspec- 
 tion of Figs. 19-23 may serve to clear up any doubtful 
 points, both in dimensioning and in construction. 
 
 OBLIQUE SCALE 
 
 (82) If equal distances be measured from along 
 the axes OA, OB and OC, Fig. 24, the distance along 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 135 
 
 Oblique Projection of Stuffing Box. 
 
 Fig. 19 
 
136 
 
 MECHANICAL DRAFTING. 
 
 Oblique Projection of Shaft Coupler. 
 Fig. 20 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 137 
 
 Oblique Projection of Post Hanger. 
 
 Fig. 21 
 
138 
 
 MECHANICAL DRAFTING. 
 
ISOMETRIC AND OBLIQUE PROJECTION. 139 
 
 r 
 
 Oblique Projection of Flanged Pipe Tee. 
 
 Fig. 23 
 
140 
 
 MECHANICAL DRAFTING. 
 
 OC will appear to be longer than those along OA and 
 OB ; hence, for symmetry, it is necessary to make use of 
 
 Fig. 24 
 
 Oblique Scale for 45 Oblique Scale for 30 
 Fig. 25 
 
 the oblique scale in measuring any distance along OC. 
 The oblique scale is obtained by measuring off inches, 
 etc., on the hypotenuse of a 45, 30, or 60 triangle and 
 projecting these inches upon either of the legs for 45, 
 long leg for 30 and short leg for 60, Fig. 25. 
 
 (83) Problem 3. To draw the oblique projection of a 
 parallelepiped. 
 
 Construction. Cube V on edge. 
 
 Thru a chosen point, 0, Fig. 26, draw the three axes 
 OA, OB, and OC. Along axes OA 
 and OB measure 1" to D and S, 
 and with the oblique scale meas- 
 ure V along OC to R. Com- 
 plete the parallelograms ODMR, 
 OSLR,'and DNSO; then the re- 
 maining faces may easily be 
 added. 
 
 N. 
 
 V 
 
 \ 
 
 \ 
 
 II 
 
 Fig. 26 
 
 CIRCLES 
 
 (84) Point E, in face TLRM, Fig. 27, is the center 
 of a circle %" diameter. Since this is the face of true 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 141 
 
 circles, the circle may be constructed with the compass. 
 If it is desired to draw the projections of circles lying 
 in faces TNSL or NTMD the 8-point method explained 
 in isometric projection may be used. In cases where 
 
 rapidity of construction is more important than sym- 
 metry, it is common practice among draftsmen to omit the 
 use of the oblique scale altogether. Then if the oblique 
 axis be drawn at an angle of 30 degrees to the horizontal, 
 it will be noted, in Fig. 28, that face NM is now of such 
 shape as to convert the oblique projection of any circle 
 placed in that face into an isometric projection, and the 
 mechanical method of constructing that isometric pro- 
 jection, shown in Fig. 12, can and should be used. If, 
 on the other hand, the oblique axis be drawn at an angle 
 of 60 degrees to the horizontal, Fig. 29, the face NL is 
 now of such shape as to convert the oblique projection 
 of any circle placed in it into an isometric projection 
 which can be constructed mechanically by the method of 
 Fig. 12. 
 
142 
 
 MECHANICAL DRAFTING. 
 
 With some care it will usually be possible, in making 
 the oblique projection of any object containing circles, 
 so to place the object that the oblique projections of 
 some of the circles are true circles, while the projec- 
 tions of the remainder become isometric when the ob- 
 lique axis is drawn either at 30 or 60 degrees to the 
 horizontal. 
 
 Fig. 29 
 
 IRREGULAR OBJECTS 
 
 (85) All that has been said on this subject under 
 isometric projection applies as well in oblique projection. 
 It is perhaps unnecessary to suggest that when making 
 any obKque projection care should be taken so to place 
 the object that most of the circles will appear as true 
 circles. 
 
 SHADES AND SHADOWS IN ISOMETRIC AND OBLIQUE 
 PROJECTION 
 
 (86) Shades and shadows, in isometric projection 
 as in orthographic projection, are used merely for the 
 
ISOMETRIC AND OBLIQUE PROJECTION. 143 
 
 natural appearance which they give to a drawing. Hence, 
 as in orthographic projection, the draftsman has con- 
 siderable freedom in determining both the direction and 
 the length of the shadows. Before proceeding with a 
 problem in shades and shadows it will perhaps be well 
 to define a few of the terms and state the fundamental 
 principles which govern construction. 
 
 Direct light. All light which comes to any body di- 
 rectly from the source (the sun, arc lights, etc.) is known 
 as direct light. 
 
 Indirect light. All light which reaches objects in an 
 indirect way, e. g., by reflection from other objects which 
 are in direct light, is known as indirect light. 
 
 Shade. Any portion of the surface of an object from 
 which the direct light is excluded by some part of the 
 same object is said to be in shade. This shaded surface 
 may also be known as a shade. 
 
 Shadow. Any portion of the surface of an object from 
 which the direct light is excluded by some part of another 
 object is said to be in shadow, and for convenience may 
 be .called a shadow. 
 
 PRINCIPLES 
 
 1. All rays of light in these problems are regarded as 
 parallel; hence, when the direction of the first ray has 
 been assumed, all others must be considered parallel to it. 
 
 2. The shade or shadow of a given point on a given 
 surface is the point in which a ray thru the given point 
 pierces the given surface. 
 
 3. Any ray used to determine the shade or shadow of 
 a given point may in reality be a ray of light ; however, 
 
144 
 
 MECHANICAL DRAFTING. 
 
 in this discussion it will be known as a shadow ray; see 
 Miller's Descriptive Geometry, Art. 124. 
 
 4. If a line AB is parallel to a plane, e. g., H, the 
 shadow of AB on H is parallel and equal in length to AB. 
 
 Fig. 30 
 
 5. If lines AB and CD are parallel the shadows of 
 AB and CD on any plane must be parallel, i. e., the 
 shadows of parallel lines are parallel. 
 
 6. If a line AB is oblique to H, AB and its shadow 
 on H will meet at the point in which AB pierces H. 
 
 7. The shadoivs of parallel lines on parallel planes 
 are parallel. 
 
 (87) Problem 4. To find the isometric or oblique 
 projection of the shade and shadow on H of a given object. 
 
 Given. Isometric and oblique projections of Cross, 
 Figs. 30 and 31. 
 
ISOMETRIC AND OBLIQUE PROJECTION. 
 
 145 
 
 Req'd. Isometric and oblique projections of shade and 
 shadow on H. 
 
 Beginning with point as an origin, a line may be 
 drawn in any desired direction, e. g., Oa, to represent the 
 shadow of OA, and point a assumed in any desired posi- 
 
 
 f \ 
 
 
 \ 
 
 1 
 
 \ 
 
 1 
 
 IP 
 
 
 Pig. 31 
 
 tion as the shadow of point A. Aa is the isometric pro- 
 jection of the shadow ray thru A, and all other shadow 
 rays must be parallel to Aa. Since AB is parallel to H, 
 its shadow ab is parallel and equal in length to AB. BC 
 is parallel to OA, hence its shadow be is parallel to Oa, 
 and c is determined by shadow ray Cc. CD is parallel to 
 H, hence its shadow cd is parallel and equal in length to 
 CD; d may likewise be located by the shadow ray T)d. 
 Since the plane GCDK is parallel to H, the shade of GE 
 on this plane is parallel to Oa, see Principle 7, and e is 
 located by the shadow ray from E. EF is parallel to 
 
146 MECHANICAL DRAFTING. 
 
 GCDK, hence the shade line from e is parallel to EF; 
 to find the shadow of F draw the shadow of MF parallel 
 to Oa; the intersection of this shadow line with the ray 
 thru F locates f. The shadow of EF is paralled to cd; 
 fn is parallel and equal in length to FN. It is readily 
 seen from the direction of Oa that the face AOM must be 
 in shade, likewise BCD and GEFK and space KGeh. 
 
 The isometric projections of the shadows of the re- 
 maining points are located successively as those already 
 found. 
 
j MACHINE SKETCHING. 147 
 
 CHAPTER 8 
 
 MACHINE SKETCHING 
 
 (88) Definition. A machine sketch may be roughly 
 denned as a freehand working drawing. 
 
 To the engineer no one accomplishment is of more 
 value than the ability to make rapidly accurate, legible 
 machine sketches. 
 
 A draftsman or shop foreman may be called upon at 
 any time to make a hasty sketch of some broken machine 
 part which perhaps cannot be removed without shutting 
 down the machine for a day or two. 
 
 A construction engineer putting in some new machin- 
 ery may find that some plates, fixtures, etc., designed 
 especially for the job, are all wrong, and he must imme- 
 diately send in sketches of what is wanted. 
 
 A bridge engineer may find his work held up by the 
 breaking or absence of some peculiarly shaped piece, or 
 may need some special fixtures to handle difficulties pecu- 
 liar to the job. 
 
 Likewise, it is understood that all machine forms are 
 devised in the mechanic's brain and must be placed on 
 paper in some approximate form before it is possible to 
 make a mechanical working drawing. 
 
 In all of these and hundreds of other cases which are 
 inevitable, the ability to sketch rapidly and well is indis- 
 pensable, and the man who finds himself called upon to 
 make a sketch and is not well grounded in its principles, 
 will find himself seriously handicapped. 
 
 PAPER 
 
 (89) It will be seen that the nature of the situations 
 
148 MECHANICAL DRAFTING. 
 
 which require sketching will demand the use of scratch 
 paper or a notebook. Cross-section paper is invaluable 
 for this purpose, as it aids materially in the rapid and 
 accurate sketching of the several views. 
 
 NATURE OF DRAWING 
 
 (90) As in a mechanical working drawing, a machine, 
 sketch consists of a number of views (top and front; top, 
 front, and left end, etc.) of a machine or machine part. 
 These views are true orthographic projections, hence 
 projections of each other, as in working drawings. Never 
 show more views than are necessary to explain clearly 
 the construction; of course, two are a minimum; varia- 
 tions in this respect will be mentioned later. 
 
 PENCIL SKETCH STROKE 
 
 (91) For sketching it will be better to use a com- 
 paratively soft pencil, H or 2H, as it is desirable to show 
 marked distinction between the outlines of the object and 
 dimension and section lines. 
 
 In drawing lines, whether short or long, the sketch 
 stroke should be used. The sketch stroke is merely a 
 succession of short strokes in the desired direction, and, 
 as a result, the line will, of course, be somewhat ragged, 
 consisting of a number of short overlapping lines. How- 
 ever, by this method it will be found possible to approxi- 
 mate a straight line much more closely than by a con- 
 tinuous stroke. 
 
 SIZE OF DRAWING 
 
 (92) The work being freehand and done usually 
 under adverse conditions, sketches are not made to 
 scale; numerical dimensions are depended upon en- 
 
MACHINE SKETCHING. 149 
 
 tirely for sizes. As an aid in approximating propor- 
 tions of the different parts of a machine, the follow- 
 ing scheme will be found useful: Suppose after care- 
 ful inspection it is decided that only two views are 
 necessary, and these front and right end. You have 
 perhaps a 5 x 7 notebook at hand and must place these 
 two views, with dimensions, on this size sheet. Estimate 
 the ratio of the length of the object to its width and 
 height and block out roughly on the sheet the proper pro- 
 portional spaces, for the two views, making them as largo 
 as possible. Then measure off on a lead pencil with the 
 thumb-nail a distance equal to the length you have given 
 the space for the front view, and, holding the pencil hori- 
 zontally and about 1' from the eye, move off from the 
 machine until the space from the end of the pencil to the 
 thumb-nail just covers the length of the machine. Stand- 
 ing in this position and using the pencil in this manner, 
 the several parts of the machine may be rapidly sketched 
 in their proper sizes. 
 
 PROCEDURE 
 
 (93) In making a machine sketch, the greatest speed 
 and accuracy will be attained by following some system. 
 The following will be found valuable : 
 
 1. Decide on the number of views necessary, and 
 decide which these should be. 
 
 2. Estimate ratio of length to width of machine and 
 block out on sheet proportional spaces for above views. 
 
 3. Sketch in all outlines (working on all views at 
 the same time). Do not attempt to finish one view en- 
 tirely before working on the other ; when a line is placed 
 on one view, place its projection on the other view so 
 that all views are finished at approximately the same 
 time. 
 
150 MECHANICAL DRAFTING. 
 
 4. Sketch in dimensions, auxiliary, and section lines. 
 The reason for placing on dimension lines while making 
 up the views is, that each detail of the piece as it is 
 drawn may suggest a necessary dimension that perhaps 
 would be overlooked if left until later. A break should 
 be left in each dimension line. No attempt need be made 
 here to distinguish between outlines and other lines. 
 
 5. Go over the sketch carefully and increase the 
 weight of outlines so that the construction shows easily. 
 
 6. Obtain from the machine with calipers and rule 
 all dimensions already indicated on sketch. Always 
 place on overall dimensions as a check. 
 
 7. Be liberal with notes. 
 
 SHORT CUTS 
 
 (94) To save time, the following short cuts are 
 permissible : 
 
 1. In drawing objects of familiar shape, wheels, etc., 
 the hub, two spokes, and a short portion of the rim is 
 sufficient. 
 
 2. -Where objects are symmetrical with respect to a 
 center line, e. g., gate valves, etc., it is sufficient to show 
 only one-half of object, limiting the portion drawn by 
 the center line. The other half may be drawn in when 
 time permits, if desired. 
 
 3. Where objects are symmetrical about two center 
 lines at right angles to each other, it will be sufficient to 
 show only one-fourth of the object. 
 
 4. Where any part cannot be shown well in detail, 
 e. g., bolts, holes, fasteners, etc., explanatory notes may be 
 substituted e. g., %" drill; %" x 10 pi. tap; %" He?*. 
 Hd. MacJi. Sc.; etc. 
 
PERSPECTIVE. 151 
 
 CHAPTER 9 
 
 PERSPECTIVE 
 
 (95) Tho it is impossible to give here any complete 
 explanation of the principles of perspective, it has been 
 deemed advisable to attempt sufficient explanation to 
 enable one to understand a few of the basic principles. 
 
 It is readily seen that no one view of a working draw- 
 ing of any object can present to the eye the natural 
 appearance possessed by a crayon or charcoal drawing. 
 The reason is, that, in making a working drawing the 
 eye was imagined at an infinite distance from the object, 
 an assumption so unnatural as to give rise immediately to 
 results of an unnatural appearance. 
 
 PERSPECTIVE DRAWING 
 
 (96) Definition. A perspective drawing of an object 
 is such a representation of that object on a given plane 
 or sheet of paper as will present the same appearance as 
 the object itself when the eye is in a certain position with 
 respect to the object. 
 
 The plane on which the perspective drawing is made 
 is called the picture plane, and, for reasons which need 
 not be given here, is usually taken vertically. 
 
 PRINCIPLES OF CONSTRUCTION 
 
 (97) The principle on which perspective construc- 
 tion is based is as follows : The vertical picture plane 
 is placed between the eye and the object (that the draw- 
 ing may be smaller than the object), and lines of sight 
 or visual rays drawn from the eye to the various points 
 
152 
 
 MECHANICAL DRAFTING. 
 
 of the object. The points in which these lines pierce the 
 picture plane are respectively the perspectives of the 
 corresponding points of the object. If lines be drawn 
 connecting these piercing points in their proper order, a 
 perspective drawing of the whole object is obtained. 
 Fig. 1. 
 
 PICTURE PLANE AND POSITION OF OBJECT 
 
 (98) Since perspective drawings are made mostly 
 from working drawings, the vertical plane of ortho- 
 
 Picture Plane 
 
 Fig. 1 
 
 graphic projection is used as the picture plane and the 
 object placed in the third angle. 
 
 POSITION OF POINT OF SIGHT 
 
 (99) The point of sight is, of course, in front of the 
 vertical plane, and may be in either the first or fourth 
 angles, according to the nature of the view desired; i. e., 
 if it is desired to make a drawing showing tlie appear- 
 ance of the object when directly in front of it, the point 
 of sight would be in the fourth angle. 
 
 PRINCIPAL POINT IN PERSPECTIVE 
 
 (100) The projection of the point of sight on the 
 vertical plane is called the principal point in perspective, 
 and is of prime importance in construction. Inasmuch 
 
PERSPECTIVE. 
 
 153 
 
 as the vertical projections of points are designated thus, 
 a', b', c', etc., the vertical projection of the point of sight, 
 S, will be indicated by s'. 
 
 PRINCIPAL POINT THE VANISHING POINT OF LINES 
 PERPENDICULAR TO THE PICTURE PLANE 
 
 (101) It is a familiar fact that as one stands 
 near a long straight section of railroad track the two 
 lines of rails appear to meet off in the distance. So 
 it is with any set of parallel lines; if the eye follows 
 them for a distance and, when speaking geometric- 
 
 Fig. 2 
 
 ally, we give this distance a value of infinity they 
 all appear to meet in one point. This point we call 
 their vanishing point. When our line of sight follows out 
 these parallel lines to infinity, where they appear to meet, 
 for all practical purposes the line of sight is parallel to 
 the given set of lines. Eeference to Fig. 2 may serve 
 to make this explanation clearer. Point S represents 
 the position of the eye. A cube BD rests on a horizontal 
 
154 MECHANICAL DRAFTING. 
 
 plane on the other side of the picture plane. The four 
 parallel edges, AB, CE, etc., of the cube are produced as 
 indicated by dotted lines to the right; if they are pro- 
 duced an infinite distance they will appear to meet, and 
 the line of sight from S to the apparent meeting or 
 vanishing point is the line thru S and V. Then, as ex- 
 plained above, if SV meets AB; CE, etc., at infinity, it 
 is parallel to them. But AB, CE, etc., are perpendicular 
 to the picture plane; therefore the line thru S and V out 
 to this vanishing point is also perpendicular to the pic- 
 ture plane and must pass thru s', the projection of S on 
 the picture plane. As viewed from point S, the four 
 edges, AB, CE, etc., which we have produced to infinity, 
 do not in reality appear to be parallel lines forming the 
 edges of a long prism, but seem to represent the four 
 edges of a long pyramid. To return to the perspective, 
 suppose we wish to represent this long pyramid on the 
 picture plane as seen from S. According to Art. 97, 
 lines are drawn from S to the several points of the 
 pyramid; the line from S to the imaginary apex at in- 
 finity pierces the picture plane at s'; and the lines from 
 S to A, C, D, and F pierce the picture plane at a^ Ci di fi ; 
 then ai d di / a -s' is the perspective of the pyramid. From 
 this explanation it is seen that the perspective of all lines 
 perpendicular to the picture plane meet at s', the vertical 
 projection of the point of sight. For this reason s' is 
 called the vanishing point of perpendiculars. The fact 
 that perpendiculars do converge at s' affords an easy 
 method of constructing the perspective of any object 
 when placed in a certain position. Lines from S to the 
 other points of the cube are seen to pierce the picture 
 plane in points on the perspectives of these perpendicu- 
 lars, giving the figure &i a t Ci d /! g^. This figure repre- 
 
PERSPECTIVE. 
 
 155 
 
 sents the cube as seen from S. Face ABEC is not visible 
 from S. 
 
 THE HORIZON IN PERSPECTIVE 
 
 (102) Any line which is perpendicular to a vertical 
 plane is horizontal. In Fig. 2 the lines AB, CE, etc., are 
 horizontal lines and, when produced an infinite distance, 
 
 appear to meet in a point on what we commonly call the 
 horizon. Then the line of sight from S to this meeting 
 point becomes a horizontal line, and the perspective of 
 the horizon will be the horizontal line drawn thru the 
 point s'. The horizontal line lying in the picture plane 
 
156 MECHANICAL DRAFTING. 
 
 and passing thru the vertical projections of the point of 
 sight, s', is also called the horizon. 
 
 SPECIAL POSITION OF THE OBJECT 
 
 (103) If the cube in Fig. 2 be moved until face ACDF 
 coincides with the picture plane, then this face becomes 
 its own perspective and each line on this face is shown 
 in its true value ; i. e., a circle shows as a true circle, etc. 
 From this it follows that the perspective of any circle 
 whose plane is parallel to the picture plane will be a true 
 circle; its diameter will be less or greater than the true 
 diameter, however. 
 
 MECHANICAL CONSTRUCTION OF A PERSPECTIVE 
 
 (104) Inasmuch as all lines in perspective are shorter 
 than the lines which they represent, except in the case of 
 lines which lie in the picture plane, it will be best to put 
 one face of the object or one face of a circumscribed 
 parallelepiped into coincidence with the picture plane, in 
 order that we may have a foundation of actual measure- 
 ments on which to base our construction. 
 
 COORDINATES 
 
 (105) The position of the point of sight with respect 
 to some chosen point, A, of the object will hereafter be 
 given as follows: 
 
 x = distance of point of sight to right or left of A 
 as x is + or . 
 
 y distance of point of sight above or below A as y 
 is + or . 
 
 z = distance of point of sight before the point A; 
 e. g., x == 3", y=- 4", z = 6" locates S 3" to the right 
 and 4" below A and 6" before the picture plane. 
 
PERSPECTIVE. 
 
 157 
 
 (106) Problem 5. To draw the perspective of a cube 
 " on edge, one face of the cube coinciding with the 
 
 picture plane; x = 2", 2/ = l", 2 = 4". A is taken at 
 
 corner A. 
 
 Fig. 3 
 
 Construction. See Fig. 3. 
 
 Draw well toward the top of the sheet a horizontal line 
 G. L., the intersection of the horizontal and vertical 
 planes. Since the picture plane coincides with the verti- 
 cal plane this line, Gr. L., represents the picture plane as 
 
158 MECHANICAL DRAFTING. 
 
 seen from the top. Construct in a convenient position the 
 top view b-fc-da-gj of the cube, the line da-fc, which repre- 
 sents the front face of the cube, coinciding with G. L. At 
 any desired distance directly below the top view, draw the 
 square fli/id dj. which is the front view of the cube. 
 
 The point of sight 8 is to be located by the three co- 
 ordinates given with reference to the point A on the cube. 
 First, locate 8 as viewed from above. The top view of 8 
 (lettered s) is 2" to the left of a (x = 2) and 4" in front 
 of a (z=4"). The square b-fc-da-gj, G. L., and s now 
 represent respectively the cube, the picture plane, and the 
 point of sight as they appear looking down from above. 
 Second, locate S as viewed from the front. The front 
 view of 8 (lettered s') is 2" to the left of a, (x= -2) and 
 1" above a t (y=l"). The square a^Cidi and s' now rep- 
 resent respectively the cube and the point of sight as 
 viewed from the front. 
 
 The square a-ifiddi is the perspective of the front face 
 of the cube since this face lies in the picture plane. Draw 
 lines from Oi, /i, Ci, and d to s'. This figure s' ckfiCtdi 
 then is the perspective of the long pyramid spoken of in 
 Art. 101. The perspectives of the edges of the cube that 
 are perpendicular to the picture plane will lie along these 
 lines just drawn to s'. For example, the perspective of 
 the edge AG is a-^g^ lying along ch s' and it is only neces- 
 sary to locate g on this line. To locate g^ draw sg and 
 where it crosses G. L. at v drop a perpendicular to G. L. 
 until it intersects Oi s'. Since sj coincides with sg, j^ will 
 lie directly below g^ on d^ and the perspective of the left 
 side of the cube is completed as a^g^id^. A horizontal line 
 from gi produced until it interesects /!$', completes the 
 perspective of the cube. It is easily seen that sg is the 
 
PERSPECTIVE. 159 
 
 top view of a line of sight from 8 to G and was drawn to 
 ascertain the distance v d to the left of the edge FD of the 
 cube at which the line of sight pierces the picture plane, 
 
 It is desired to place a small pyramid on top of the 
 cube, the edges of its base parallel to the edges of the cube 
 and its apex P directly above the center of the top face. 
 Construct the top and front views of the pyramid in place 
 and proceed with the construction of the perspective of 
 the base as shown. The perspective p of the apex is the 
 point in which the line of sight sp pierces the picture 
 plane and is found by dropping a perpendicular from the 
 point where sp crosses G. L. until it meets s' p'. The per- 
 spective of the pyramid is then readily completed. 
 
 In certain instances, a left side view will be an addi- 
 tional aid in constructing the perspective. In Fig. 3, the 
 square l"g" f'a," d"<f'j", & L, and s" represent 
 respectively the cube, the picture plane and the point of 
 sight as viewed from the left. The line s"p" represents 
 the line of sight from s to the apex p of the small pyramid 
 as viewed from the left and a horizontal line drawn from 
 v" meets s'p' at p. It will be readily seen that the per- 
 spective could have been determined from the left side 
 and front views without the use of the top view at all. 
 The use of both top and left side views is usually unneces- 
 sary. 
 
 CIRCLES IN PERSPECTIVE 
 
 (107) The 8 point method may be used in construct- 
 ing circles in perspective. This is illustrated on the cube 
 in Fig. 3. The diagonals can easily be drawn and the 
 points of tangency of the perspective with the upper and 
 lower lines / A g^ and d 1 j determined by drawing a ver- 
 tical line thru the intersection of the diagonals. 
 
160 MECHANICAL DRAFTING. 
 
 IRREGULARLY SHAPED OBJECTS 
 
 (108) Any irregularly shaped object may be easily 
 drawn in perspective by first enclosing the object in a 
 parallelepiped and referring the several constructions 
 of the object to lines of the parallelepiped. 
 
 POSITION OF POINT OF SIGHT 
 
 (109) Considerable care and judgment must be used 
 in placing the point of sight, for it is easily understood 
 that a house viewed from a point only two feet in front 
 of it would look absurd; however, its perspective can be 
 constructed as easily under such circumstances as any 
 other. It is well to estimate approximately from what 
 particular position we would likely view that object to 
 obtain the b&st view, taking into account the size of the 
 object in this "estimate. The point of sight may then be 
 placed accordingly. For large objects a safe rule is to 
 place the point of sight in front of the object a distance 
 equal to twice the greatest dimension. For smaller 
 objects we may increase this to 4 or 5 times the greatest 
 Dimension. 
 
APPENDIX 
 
162" MECHANICAL DRAFTING. 
 
 PHOTOGRAPHIC REPRODUCTIONS 
 
 Blueprinting. Blueprinting is in short a process of 
 simple photographic reproduction on sensitized paper, 
 of drawings which have been made on some translucent 
 material; this material may be tracing cloth, tracing 
 paper, or ordinary paper oiled after the drawing has 
 been finished. In common practice the process is some- 
 what rough as one would infer from a glance at the 
 average print; however, with care it can be carried 
 nearly to the same limits of refinement as other photo- 
 graphic printing. 
 
 BLUEPRINT PAPERS 
 
 Occasions may arise when it is necessary to sensitize 
 paper for blueprinting; however, unless absolutely nec- 
 essary no draftsman should ever bother to coat his own 
 paper, for it is a tedious and most unsatisfactory proc- 
 ess. The machine-coated papers sold by any of the in- 
 strument companies in 10 or 50-yard rolls of any width 
 and of any desired thickness or quality of paper is 
 cheap, keeps well for months in a tin tube, and always 
 gives better results than paper coated by the amateur. 
 For prints which must stand extra hard use, either 
 mounted paper (cloth-backed paper) or blueprint cloth 
 (a smooth, hard-surfaced, sensitized cloth) should be 
 used; the latter, however, seldom gives the sharp detail 
 obtainable on paper. Below is tabulated information 
 that will be of value in ordering papers or cloth. 
 
APPENDIX. 
 
 163 
 
 Blue Print Paper and Cloth 
 
 PAPER 
 
 CLOTH 
 
 WEIGHT 
 
 USE 
 
 WEIGHT 
 
 USE 
 
 Extra thin 
 
 For sending thru mail. 
 Not satisfactory for 
 shop use, too thin. 
 
 Extra thin 
 
 L/arge prints which 
 are to receive extra 
 hard wear. 
 
 Thin 
 
 For large prints that 
 would be too bulky on 
 heavier paper. 
 
 Medium 
 
 Small maps, moderate 
 sized prints that re- 
 ceive extra wear. 
 
 Medium 
 thick 
 
 Best for all ordinary use, shop, construction work, etc. 
 
 Thick 
 
 For durable small prints; maps, land plots, etc. 
 
 Printing Speed in Bright Sunlight 
 
 Regular 
 
 Rapid 
 
 Extra Rapid 
 
 Elec. Rapid 
 
 4 min. 
 
 2 min. 
 
 40 sec. 
 
 25 sec. 
 
 In ordering paper be sure to state the printing speed desired; 
 e. g., 1 roll; 50 yds. x 36 in., Extra Thin, Electric Rapid, Blue Print 
 Paper. 
 
 TO SENSITIZE PAPER 
 
 "unsized" and well-washed papers are 
 
 Paper. Only 
 
 suitable for blueprinting. The size used on many papers 
 to give it a glossy and easy writing surface discolors the 
 blueprint solution immediately. Likewise paper from 
 which the sulphur, used in its manufacture, has not been 
 well washed will discolor. Practically any unsized 
 "bond" or "parchment" paper will be found satisfac- 
 tory for printing. 
 
 Solution. The formula in most common use for the 
 sensitizing solution is: (1) Eed prussiate of potash, 1 
 oz. ; water (distilled), 4 oz. ; (2) double citrate of iron 
 and ammonia, 1 oz. ; water (distilled), 4 oz. As long as 
 
104 MECHANICAL DRAFTING. 
 
 these solutions are kept separate sunlight has no effect 
 upon them. However, the second solution should be 
 kept in a well stoppered bottle of dark colored glass. 
 
 To sensitize the paper, mix equal volumes of the 
 above solutions and apply either with a camel's hair 
 brush, brushing first horizontally, then vertically, to 
 insure even coating, or float the paper for a few seconds 
 in a shallow granite pan partially filled with the solu- 
 tion, and hang by one corner to dry. This sensitizing 
 must of course be done in a dark room. If the solution 
 of citrate of iron is kept too long it may mold and spoil ; 
 hence, as the crystals dissolve quite readily it may be 
 best to make this solution only when it is to be used and 
 then only what is needed. The bottle in which the citrate 
 is kept should be glass stoppered to prevent moisture 
 from melting down the crystals. The prussiate does not 
 dissolve so readily and as it does not spoil it can be kept 
 in solution in any quantity. 
 
 VANDYKE SOLAR PAPER 
 
 Vandyke Solar Paper, sometimes called "Brown 
 Print " paper, is a brown paper used in making neg- 
 atives for positive printing. A print is made on Van- 
 dyke paper from a tracing, the inked side of the tracing 
 being in this case turned to the paper, so that a reversed 
 print is obtained. The lines of the drawing show up 
 white on a deep brown background. This paper is then 
 rubbed with oil to make it more transparent and positive 
 blueprints are made from it, the brown side of the nega- 
 tive being turned toward the blueprint paper. In this 
 final print the lines of the drawing show up blue on a 
 ivhite background instead of the reverse in direct print- 
 ing from the tracing. 
 
APPENDIX. 165 
 
 WASHING AND FIXING VANDYKES 
 
 Vandyke paper has been sufficiently exposed when 
 the surface not covered by the black lines of the trac- 
 ing has turned a light bronze color. After washing 
 for a few minutes, face down in the tank, the print should 
 be fixed with a solution of 1 oz. of hyposulphite of soda 
 to 1 qt. of water. The print may be laid on a board and 
 the solution applied with a brush or better still the print 
 may be floated face down, in a granite pan partially 
 filled with the hypo solution ; one brushing or a few sec- 
 onds floating is sufficient. The print should then be 
 washed again face down, to remove the surplus hypo. 
 
 TO TRANSPARENTIZE VANDYKES 
 
 It is possible to obtain positive prints from unoiled 
 Vandykes; however, if the negative has been rendered 
 more transparent by oiling the printing time will be 
 materially reduced. Any clear oil or white grease 
 will answer for this purpose, white tube vaseline being 
 perhaps the most convenient. The following formula 
 gives a transparentizing oil that works well: 4 oz. 
 banana oil, lOc tube white vaseline. (Mix the two by 
 heating slightly and keep in a stoppered bottle.) The 
 banana oil furnishes a quick " drier'' and the vaseline a 
 permanent oil. If there is much transparentizing to be 
 done it is well to keep a ball of waste, soaked in the 
 above solution, in a covered tin can. Never apply more 
 grease than will dry in a few minutes and be sure to 
 oil the side of the paper which is to be turned toward 
 the light. Unless necessary never use paraffin for trans- 
 parentizing; it renders the paper very brittle and any 
 wrinkles in a paraffined negative show plainly on the 
 print. 
 
166 MECHANICAL DRAFTING. 
 
 POSITIVES ON OLD VANDYKE PAPER 
 
 In making positive prints on old Vandyke paper 
 some little care must be exercised. When printed and 
 washed the unexposed or white parts turn decidedly 
 yellow; this can be prevented if the print is merely 
 dipped in the water to wet the surface and start the 
 printing out and immediately floated on the fixer; the 
 fixer will print out the lines and prevent the background 
 from turning yellow. These precautions are not neces- 
 sary in making negatives on old paper, for tho unexposed 
 parts may turn yellow the negative will print well when 
 oiled. 
 
 BLUEPRINTING FROM TYPEWRITTEN SHEETS 
 
 To obtain clear sharp prints from typewritten sheets 
 a moderately thin' hard surfaced paper and new black 
 typewriter ribbon should be used. If there is much 
 work to be done it will be well to obtain an extra 
 heavily inked ribbon. In typewriting place under the 
 the paper a sheet of black carbon paper with carbon face 
 toward the paper; thus an impression is obtained on both 
 sides of the paper. Use each sheet of carbon paper only 
 once for this purpose. 
 
 In oiling, one may not rub these sheets, as the carbon 
 will smear. Instead, lay over the typewritten sheet a 
 square of oily cotton flannel, then a sheet of heavy paper 
 and roll with a small picture mounting roll. Or better, 
 if time permits, lay pieces of oily cotton cloth between 
 the sheets and weight down with a heavy book for sev- 
 eral hours. Arrange sheets and cloth as follows : Paper, 
 cloth, two sheets of paper, cloth, two sheets of paper, 
 cloth, etc. In printing from these sheets, over expose 
 the paper slightly and wash in water to which hydrogen 
 
APPENDIX. 167 
 
 peroxide has been added in the proportion of % tea- 
 spoonful to 2 gallons water; the hydrogen peroxide will 
 bring out the over exposed parts and deepen the blue. 
 The above solution can be used to advantage in washing 
 any blueprints; a sharper contrast between the white 
 lines and blue background can be obtained. 
 
 PRINTING FROM OLD BLUEPRINTS 
 
 Occasionally reproductions of drawings are wanted 
 when the tracings are not available. By use of the 
 " Direct Copier " of the Frederick Post Co., Chicago, 
 an old blueprint may be rendered sufficiently dense to act 
 as a good negative. This "Direct Copier" consists of 
 two concentrating solutions to be applied to the old blue- 
 print to deepen the blue; the transparentizing oil must 
 then be used to clear up the white lines. If the "Direct 
 Copier " is not available and there is not sufficient time 
 for a tracing a fairly good positive may be made from a 
 blueprint by merely transparentizing it. 
 
 PRINTING FROM HEAVY CARDBOARD 
 
 If it is desired to make a blueprint of a drawing 
 mounted or printed on heavy cardboard or of a draw- 
 ing on mounted paper, the face of the drawing should 
 be soaked with alcohol and immediately clamped in 
 the printing-frame. The alcohol will not evaporate 
 while closed in the frame nor will it dissolve the blue- 
 print solution if it should soak thru the cardboard. The 
 length of time required for printing will have to be 
 learned from experiment. 
 
 PRINTING FROM COORDINATE PAPER 
 
 Coordinate paper printed in red gives better blue- 
 prints than the paper printed in blue or green. Always 
 
168 MECHANICAL DRAFTING 
 
 transparentize the coordinate paper before printing; it 
 will save time in printing and give better results. 
 
 Positive blueprinting of typewritten sheets. Excel- 
 lent negatives for positive printing of typewritten 
 sheets may be made from new black carbon paper as fol- 
 lows : Remove the ribbon from the typewriter and place 
 the carbon paper in the machine, face up, with a sheet of 
 thin hard surfaced paper over it. A reversed impres- 
 sion will of course be obtained on the back of this sheet 
 of paper and the better the quality of paper the more 
 clear cut will be the letters on the carbon sheet. The 
 reason for placing the carbon with face to the .cover sheet 
 is to obtain such an impression as to make it possible to 
 place the carbon side of the paper toward the glass of 
 the printing frame instead of toward the blueprint paper. 
 
 Handle the carbon paper very carefully; a finger 
 mark or smudge may easily ruin the negative. 
 
 The time for printing will have to be determined by 
 experiment ; it should be somewhat longer than for print- 
 ing from tracings. 
 
APPENDIX. 169 
 
 LINE ENGRAVING ON ZINC 
 
 Process. Line engraving on zinc is essentially an 
 etching process and the procedure is as follows : A glass 
 plate is coated with a sensitive solution and a negative 
 made thereon, by the use of a camera, from the drawing 
 submitted. After development the film negative is 
 removed from the glass plate and transferred to another 
 glass plate in a reverse position, thereby converting it 
 into a positive film. A second negative is now obtained 
 upon the sensitized surface of a polished zinc plate. A 
 compound composed largely of printer's ink and grease 
 is applied to the surface of this negative. This coating 
 adheres to the portions corresponding to the lines of the 
 drawing and when the plate of zinc is immersed in acid 
 the surface is eaten away except where protected by the 
 ink and grease compound. The result is a duplicate on 
 the zinc plate of the original drawing. 
 
 Drawings. In order that one may secure the best 
 possible line engraving on zinc especial care should be 
 taken with the drawing. The paper used should be either 
 white or bluish white; ordinary drawing paper, tracing 
 cloth, or transparent vellum m'ay be used. Very black 
 water proof drawing ink should be used in making the 
 lines, and care should be exercised that in erasing, the 
 black lines are not dulled. If any parts of the lines are 
 faded from erasing, they are not photographed sharply 
 and the resulting lines may be somewhat ragged. So far 
 the best ink that the writer has found for this purpose 
 is the United States Blue Print Paper Company's Draw- 
 ing Ink. 
 
170 MECHANICAL DRAFTING. 
 
 Reduction. In making a drawing for etching, it is 
 best to make it of such a size that when reduced to one- 
 half or one-third of its dimensions, it will be of the desired 
 size for use ; that is, if a diagram is finally to be 4x6 
 inches,the drawing had better be made about 8x12 inches. 
 It should be remembered, however, that very fine lines 
 do not reduce in the same proportion as heavy lines. To 
 prevent very fine lines from disappearing entirely, the 
 engraver will have to use methods which perhaps will 
 increase them, and quite likely this increase will not be 
 uniform, so that in making up a drawing care should be 
 taken to make the lines about twice the desired final 
 weight. For purposes of illustration hidden lines should 
 be omitted and dimension lines should be made of sec- 
 ondary importance. Likewise, shading will be found use- 
 ful in adding to the appearance of a drawing. For best 
 appearance it is better to use printed letters than free- 
 hand. This may be done by having all material which is 
 to go on the drawing set up in type in a size about twice 
 that finally desired, printing it on gummed paper, and 
 pasting this material on the original drawing. Any lines 
 which may be placed on the original drawing, and which 
 are later found unnecessary or incorrect, may be simply 
 marked over by the draftsman, with the understanding 
 that the engraver is to paint them out; the only rigid 
 requirements are that all lines be sharp, a dense black, 
 and that the paper used be white. 
 
APPENDIX. 171 
 
 WAX ENGRAVING PROCESS 
 
 Wherever it is impossible to submit a high grade line 
 drawing from which to make the zinc line engraving, an 
 accurate pencil or ink drawing or blue print may be sub- 
 mitted to any of the companies handling wax engraving 
 work. This drawing or print is photographed on the sen- 
 sitized wax surface of a copper plate. The photographed 
 outlines are then scratched through the wax to the copper 
 plate with appropriate tools. All necessary lettering is 
 set in type and pressed into the softened wax. This wax 
 engraving is then electrotyped, backed with type metal 
 and mounted on a wooden block. Very clean cut legible 
 lines result from this process, and it seems to be used 
 very largely in making cuts of diagrams, curves, text 
 book illustrations, etc. 
 
 A slight modification of this process is to make the 
 drawing directly on the waxed covering of a copper plate, 
 omitting the photographing process. The lines of the 
 drawing are then scratched through to the copper plate 
 and the procedure is as before. This scheme of engrav- 
 ing is very expensive, and perhaps will not be found 
 profitable except as noted before in making cuts of charts, 
 diagrams, curves, etc., on which a high degree of accuracy 
 is desired. 
 
 HALF TONES 
 
 The half tone is the cut usually used in reproductions 
 of photographs, wash or charcoal drawings, etc. It is 
 perhaps unnecessary to explain in detail the process. It 
 will be better to give some suggestions on the difficulties 
 that may be encountered. 
 
172 MECHANICAL DRAFTING. 
 
 Drawings. It should be remembered always that 
 when a half tone is to be made from a photograph, wash 
 drawing, or drawing of any other description, that abso- 
 lutely everything that can be seen by the eye on the orig- 
 inal drawing or photograph, will likewise be seen and 
 reproduced by the eye of the camera. It requires ex- 
 tremely careful work to paint out by the use of an air 
 brush any lines which have been put in by mistake, and 
 such work should be left to the engraver. It is possible 
 to secure copies of high grade half tones which one may 
 find in magazines, etc., by very carefully cutting out such 
 half tones, trimming them very neatly, and pasting them 
 on a background of white paper. Extreme care must like- 
 wise be exercised in pasting down such cuts that the back- 
 ground is not smudged by glue which may run from under 
 the drawing, or by soiled fingers. The camera will surely 
 see everything that can be seen by the eye. 
 
 Photographs. The type of photograph which seems 
 to work best in the half tone process is that which is made 
 on a glazed paper. If any great amount of work is to be 
 made from photographs it will perhaps be better to con- 
 sult with some good engraver for his advice on the kind 
 of prints that he desires. 
 
APPENDIX. 
 
 173 
 
 ABBREVIATIONS 
 
 METALS 
 
 Aluminum ..... 
 Babbitt . . 
 Brass ........ 
 Bronze . . . . . . .. . 
 
 Almn. 
 Bb. 
 B. 
 Bz. 
 Cbn 
 
 Cast brass ....... 
 
 C. B. 
 
 Cast copper 
 
 C. Cop. 
 
 Cast Iron . . "*..- 
 
 C. I. 
 
 Cast steel 
 
 C. S. 
 
 Cold rolled steel 
 
 C. R. S. 
 
 Copper ....... 
 
 Cop. 
 
 Lead ...... 
 
 Lead 
 
 Malleable iron . . . . . . 
 
 M.I. 
 
 Open hearth steel . . . . . 
 
 0. H. S. 
 
 Phosphor bronze 
 
 Ph. Bz. 
 
 Steel . . . .. 4 . . . . 
 
 Steel. 
 
 Steel casting- 
 
 S. C. 
 
 Wrought iron 
 
 W. I. 
 
 Zinc . . . . ... 
 
 Zn. 
 
 Tool steel . . . . . , * . . 
 
 T. S. 
 
 Forged tool steel ..... 
 
 F. T. S. 
 
 High speed steel ..... 
 
 H. S. S. 
 
 GAGES 
 
 
 Brown & Sharpe, or American Standard 
 
 
 Wire Gage 
 
 B. & S. 
 
 Birmingham, or Stubs Iron Wire Gage 
 
 B. W. G. 
 
 National, or Roebling's, or Washburn & 
 
 
 Moen's ....... 
 
 N. W. G. 
 
 Music Wire Gage . . . " . 
 
 M. W. G. 
 
 United States Gage .... 
 
 U S. G 
 
 Twist Drill & Steel Wire Gage 
 
 T. D. G. 
 
 Stubs' Steel Wire Gage .... 
 
 S. W. G. 
 
 FASTENERS 
 
 Button head bolt .... 
 Cap screw ..... 
 Double chamfered hexagon nut 
 
 Eye bolt 
 
 Fillister head brass machine screw 
 Fillister head iron machine screw 
 
 Btn. Hd. B. 
 
 Cap Sc. 
 
 Dbl. Chmfd. Hex. Nut. 
 
 Eye B. 
 
 Fil. Hd. B. M. Sc. 
 
 Fil. Hd. I. M. Sc. 
 
174 
 
 MECHANICAL DRAFTING. 
 
 Flat head wood screw 
 Flat head stove bolt 
 Headless set screw . 
 Hexagon nut 
 L,ag screw . 
 Machine bolt 
 Machine screw nut . 
 Milled body tap bolt 
 Set screw . 
 Square nut 
 Stud bolt . 
 T-head bolt 
 
 Flat Hd. Wd. Sc. 
 Flat Hd. Stove B. 
 Hdlss. Set Sc. 
 Hex. Nut. 
 I^ag Sc 
 Mach. B. 
 M. Sc. Nut. 
 M. B. Tap B. 
 Set Sc. 
 Sq. Nut. 
 Stud B. 
 T-Hd. B. 
 
 WEIGHTS AND MEASURES, ETC. 
 
 Center 
 Center line 
 Circumference 
 Diameter 
 Foot, feet . 
 Horsepower . 
 Inch, inches 
 
 Cr. 
 C. Iv. 
 
 Circum. 
 dia. or D. 
 Ft. or ', e.g.4 
 H.P. 
 
 In. or ". e.g.4' 
 
 MISCELLANEOUS 
 
 Building 
 
 Case harden . 
 
 Company . 
 
 Counterbore . 
 
 Countersink 
 
 Cylinder 
 
 Drawing 
 
 General 
 
 Hexagon 
 
 Machine 
 
 Manufacturing 
 
 Maximum 
 
 Minimum 
 
 Specification 
 
 Square 
 
 Standard 
 
 Threads 
 
 Weight . 
 
 Finish 
 
 Bldg. 
 
 C.H. 
 
 Co. 
 
 Cbr. 
 
 Csk. 
 
 Cyl. 
 
 Dwg. 
 
 Gnl. 
 
 Hex. 
 
 Mach. 
 
 Mfg. 
 
 Max. 
 
 Mill. 
 
 Spec. 
 
 Sq. 
 
 Std. 
 
 Thds. 
 
 Wgt. 
 
APPENDIX. 
 
 175 
 
 REFERENCE TABLES 
 
 KEY FOR THE FOLLOWING TABLES OF BOLTS, NUTS, ETC. 
 
 A=0utside Diameter of Threads and Thickness of Nut. 
 
 B=Threads per Inch. I=Across Flats. 
 
 C=Tap Drill. J=Thickness Head and 
 D= Across Flats. Nut. 
 
 E=Across Corners, Hex. K=Diameter Collar. 
 
 F=Across Corners, Sq. S=Width of Slot. Deci- 
 G=Thickness of Collar. nials. 
 
 H=Thickness of Head. X=Angle of Head. 
 
 Hexagonal-Head Cap-Screw 
 
 "A | 1/4 | 5/lt)| 3/8 | 7/16J 1/2 | 9/16| 5/8 | 3/4 | 7/8 
 
 B |20 |18 |16 |14 1 13 |12 |11 |10 | 9 
 
 P | 7/16J 1/2 | 9/16| 5/8 | 3/4 | 13/16| 7/8 | 1 | 1- 1/8 
 
 B | 1/2 I .37/64| 41/64| 23/32J 55/64| 15/16J 1-1/64J 1-5/32J 1-19/64 
 
 Square-Head Cap-Screw 
 
 A | 1/4 | 5/16| 3/8 | 7/16] ' 1/2 | 9/16 | 5/8 | 3/4 | 7/8 
 B |20 |18 1 16 |14 |13 |12 |11 [10 | 9 
 
 D | 3/8 | 7/16| 1/2 | 9/16| 3/8 | 11/16 | 3/4 | 7/8 | 1- 1/8 
 
 F | 17/32| 39/64) 45/64J 51/64| 7/8 | 31 '32 | 1- 1/16 | 1-15/64] 1-19/32 
 
 Iron Set-Screw 
 
 A | 1/4 | 5/16 | 3/8 | 7/16 | 1/2 | 9/16 | 5/8 | 3/4 | 7/8 
 B | 20 I 18 | 16 | 14 I 13 I 12 | 11 | 10 | 9 
 D I 1/4 | 5/16 | 3/8 | 7/16 | 1/2 | 9/16 | 5/8 | 3/4 | 7/8 
 
176 
 
 MECHANICAL DRAFTING. 
 
 U. S. Standard Bolts and Nuts 
 
 | Rough 
 
 Finished 
 
 A 
 
 B 
 
 c 
 
 D | K 
 
 P 
 
 H 
 
 I 
 
 J 
 
 1/4 |20 |10 
 
 ' 1/2 
 
 37/64] 7/10 
 
 1/4 
 
 7/16 
 
 3/16 
 
 5/16|18 
 
 1/4 
 
 19/32) 11/16] 10/12 
 
 19/64 
 
 17/32 
 
 1/4 
 
 3/8 |16 
 
 19/64] 11/16| 51/o4| 63/64 
 
 11/32 
 
 5/8 
 
 5/16 
 
 7/16)14 
 
 23/64) 25/32] 9/10] 1- 7/64 
 
 25/64 
 
 23/32 
 
 3/8 
 
 1/2 |13 
 
 13/32) 7/8 | 1 
 
 1-15/64 
 
 7/16 
 
 13/16 
 
 7/16 
 
 9/16)12 
 
 15/32] 31/32) 1- 1/8 
 
 1-23/64 
 
 31/64| 29/32] 1/2 
 
 5/8 |11 
 
 33/64] 1- 1/16) 1- 7/32] 1- 1/2 
 
 17/32] 1 
 
 9/16 
 
 3/4 |10 
 
 5/8 
 
 1- 1/4 | 1- 7/16 
 
 1_49/64| 5/8 
 
 1- 3/16] 11/16 
 
 7/8 
 
 9 
 
 47/64] 1- 7/16] 1-21/32) 2- 1/32) 23/32) 1- 3/8 
 
 13/16 
 
 
 8 
 
 27/32] 1- 5/8 | 1- 7/8 
 
 2-19/64 
 
 13/16) 1- 9/16] 15/16 
 
 -1/8 
 
 7 
 
 61/64] 1-13/16] 2- 3/32 
 
 2- 9/16 
 
 29/32) 1- 3/4 
 
 1- 1/16 
 
 -1/4 
 
 7 
 
 1- 5/64] 2 
 
 2- 5/16] 2-53/64 
 
 1 
 
 1-15/16] - 3/16 
 
 -3/8 
 
 6 
 
 1-11/64] 2- 3/16] 2-17/32] 3- 3/32] 1- 3/32] 2- 1/8 
 
 - 5/16 
 
 -1/2 
 
 6 
 
 1-19/64] 2- 3/8 
 
 2- 3/4 
 
 3-23/64 
 
 1- 3/16 
 
 2- 5/16] - 7/16 
 
 -5/8 
 
 5-1/2 
 
 1-25/64] 2- 9/16] 2-31/32] 3- 5/8 
 
 1- 9/32 
 
 2- 1/2 
 
 - 9/16 
 
 -3/4 
 
 5 
 
 1- 1/2 
 
 | 2- 3/4 
 
 3- 3/16) 3-57/64] 1- 3/8 
 
 2-11/16 
 
 -11/16 
 
 1-7/8 
 
 5 
 
 1- 5/8 
 
 2-15/16] 3-13/32] 4- 5/32] 1-15/32] 2- 7/8 
 
 1-13/16 
 
 2 
 
 4-1/2) 1-23/32) 3- 1/8 
 
 3-19/32] 4-27/64) 1- 9/16] 3- 1/16] 1-15/16 
 
 2-1/4 
 
 4-1/2) 1-31/32] 3- 1/2 
 
 4- 1/32) 4-61/64] 1- 3/4 
 
 3- 7/16] 2- 3/16 
 
 2-1/2 
 
 4 | 2- 3/16) 3- 7/8 
 
 4-15/32] 5-31/64] 1-15/16] 3-13/16] 2- 7/16 
 
 2-3/4 
 
 4 
 
 2- 7/16] 4- 1/4 
 
 4-29/32] 6 
 
 2- 1/8 
 
 4- 3/16] 2-11/16 
 
 3 
 
 3-1/2] 2-41/64] 4- 5/8 
 
 5-11/32) 6-17/32) 2- 5/16] 4- 9/16] 2-15/16 
 
 3-1/4 
 
 3-1/2] 2-57/64) 5 
 
 5-25/32] 7- 1/16) 2- 1/2 
 
 4-15/16] 3-3/16 
 
 3-1/2 
 
 3-1/4) 3- 1/8 
 
 | 5- 3/8 
 
 6-13/64] 7-39/64] 2-11/16] 5- 5/16] 3- 7/16 
 
 3-3/4 
 
 3 
 
 3-21/64) 5- 3/4 
 
 6- 5/8 
 
 8- 1/8 
 
 2- 7/8 
 
 5-11/16) 3-11/16 
 
 4 
 
 3 
 
 3-37/64] 6- 1/8 
 
 7- 1/16] 8-41/64| 3- 1/16] 6- 1/16] 3-15/16 
 
 4-1/4 
 
 2-7/8] 3-13/16) 6- 1/2 
 
 7- 1/2 
 
 9- 3/16] 3- 1/4 
 
 6- 7/16) 4- 3/16 
 
 4-1/2 
 
 2-3/4] 4- 3/64) 6- 7/8 
 
 7-15/16) 9- 3/4 
 
 3- 7/16] 6-13/16] 4- 7/16 
 
 4-3/4 
 
 2-5/8] 4- 9/32] 7- 1/4 
 
 8- 3/8 
 
 10- 1/4 
 
 3- 5/8 
 
 7- 3/16] 4-11/16 
 
 5 
 
 2-1/2) 4- 1/2 
 
 | 7- 5/8 
 
 8^13/16] 10-49/64] 3-13/16] 7- 9/16] 4-15/16 
 
 5-1/4 
 
 2-1/2] 4- 3/4 
 
 1 8 
 
 9-15/64)11- 5/16] 4 
 
 7-15/16) 5- 3/16 
 
 5-1/2 
 
 2-3/8] 4-63/64] 8- 3/8 
 
 9-ll/16|ll-27/32| 4- 3/16] 8- 5/16] 5- 7/16 
 
 5-3/4 
 
 2-3/8| 5-15/64] 8- 3/4 |10- 3/32|12- 3/8 
 
 4- 3/8 
 
 8-11/161 5-11/16 
 
 6 
 
 2-l/4| 2-29/64| 9- 1/8 1 10-1 7/32] 12-15/16] 4- 9/16] 9- 1/16] 5-15/16 
 
APPENDIX. 
 
 177 
 
 a 
 
 a 
 
 S3 
 
 
 s 
 
 
 
 CD 
 
 w 
 
 
 
 CO 
 
 
 Q co 
 
 
 
 
 
 rj- 
 
 g 
 
 ro 
 
 S 
 
 
 i 
 
 rt 
 
 I 
 
 ! 
 
 
 fo 
 
 
 
 M 
 
 1 
 
 
 
 rH 
 
 12 
 
 o 
 
 
 ro 
 
 rH 
 
 f 
 
 o 
 
 B 
 
 <D 
 
 O 
 
 00 
 rH 
 
 I 
 
 
 
 & 
 CO 
 
 i 
 
 00 
 
 oo~ 
 
 t 
 
 s 
 
 s 
 
 
 LO 
 
 9 
 
 13 
 
 i 
 
 3 
 
 
 
 S 
 
 
 
 CJ 
 
 
 Tf 
 
 5. 
 
 s 
 
 ^ 
 
 a 
 
 -t 
 
 
 
 ii 
 
 f 
 
 ~ 
 
 cT 
 
 fNJ 
 
 
 
 CM 
 
 
 
 w 
 
 N 
 
 S5 
 
 I 
 
 rO 
 
 00 
 
 q 
 
 o 
 
 s" 
 
 Z~ 
 
 w 
 
 ^ 
 
 tf 
 
 rH 
 
 *^ 
 
 R 
 
 3 
 
 
 ^J" 
 
 
 
 o" 
 
 
 
 
 rO 
 
 ro 
 
 
 rO 
 
 
 5" 
 
 ri 
 
 ^" 
 
 
 
 2 
 
 rO 
 
 N 
 
 3 
 
 
 t 
 
 ~ 
 
 CH 
 
 3v 
 
 
 ro 
 
 ro 
 
 (N 
 
 r ~ 
 
 
 ~ 
 
 
 
 o" 
 
 
 
 
 "*3 
 
 ^ 
 
 
 VO 
 
 
 *<j 
 
 *- 
 
 -\1 
 
 rO 
 
 
 rH 
 
 
 rl . 
 
 q 
 
 
 < pq 
 
 G" 
 
 a 
 
178 
 
 MECHANICAL DRAFTING. 
 
 U. S. STANDARD SCREW THREADS. 
 
 p = pitch 
 
 FORMULA 
 
 1 
 
 No, threads per inch 
 
 d = depth = p X .6495 
 P 
 8 
 
 f = flat = 
 
 Diameter of Screw. 
 
 Threads per Inch. 
 
 Diam. at Root 
 of Thread. 
 
 Width of Flat. 
 
 1 A 
 
 20 
 
 .185 
 
 .0063 
 
 -fa 
 
 18 
 
 .2403 
 
 .0069 
 
 Yz 
 
 16 
 
 .2936 
 
 .0078 
 
 \% 
 
 14 
 
 .3447 
 
 .0089 
 
 Yi 
 
 13 
 
 .4001 
 
 .0096 
 
 ft 
 
 12 
 
 .4542 
 
 .0104 
 
 Ys 
 
 11 
 
 .5069 
 
 .0114 
 
 
 10 
 
 .6201 
 
 .0125 
 
 V* 
 
 9 
 
 .7307 
 
 .0139 
 
 i 
 
 8 
 
 .8376 
 
 .0156 
 
 1H 
 
 7 
 
 .9394 
 
 .0179 
 
 i/i 
 
 7 
 
 .0644 
 
 .0179 
 
 \y^ 
 
 6 
 
 .1585 
 
 .0208 
 
 l l / 2 
 
 6 
 
 .2835 
 
 .0208 
 
 1% 
 
 51^ 
 
 .3888 
 
 .0227 
 
 \^A 
 
 5 
 
 .4902 
 
 .0250 
 
 \y^ 
 
 5 
 
 .6152 
 
 .0250 
 
 2 
 
 4K 
 
 .7113 
 
 .0278 
 
 2/4 
 
 4;H> 
 
 .9613 
 
 .0278 
 
 2y 2 
 
 4 
 
 2.1752 
 
 .0313 
 
 2% 
 
 4 
 
 2.4252 
 
 .0313 
 
 3 
 
 31^ 
 
 2.6288 
 
 .0357 
 
 3M 
 
 3/^2 
 
 2.8788 
 
 .0357 
 
 31^ 
 
 3M 
 
 3.1003 
 
 .0385 
 
 3M 
 
 
 3.3170 
 
 .0417 
 
 4 
 
 3 
 
 3.5670 
 
 .0417 
 
 4jU 
 
 2% 
 
 3.7982 
 
 .0435 
 
 41^ 
 
 2% 
 
 4.0276 
 
 .0455 
 
 4^4 
 
 2^ 
 
 4.2551 
 
 .0476 
 
 5 
 
 
 4.4804 
 
 .0500 
 
 5/4 
 
 23^ 
 
 4.7304 
 
 .0500 
 
 5K> 
 
 2^8 
 
 4.9530 
 
 .0526 
 
 f>M 
 
 2% 
 
 5.2030 
 
 .0526 
 
 6 
 
 2M 
 
 5.4226 
 
 .0556 
 
APPENDIX. 
 
 179 
 
 FOR TAPS WITH U. S. STANDARD THREADS. 
 
 Size 
 
 No. 
 
 Size of 
 
 Size 
 
 No. 
 
 Size 
 
 Size 
 
 No. 
 
 Size 
 
 Size 
 
 No. 
 
 Size 
 
 of 
 
 of 
 
 Drill 
 
 of 
 
 of 
 
 of 
 
 of 
 
 of 
 
 of 
 
 of 
 
 of 
 
 of 
 
 Tap. 
 
 Thds. 
 
 
 Tap. 
 
 Thds. 
 
 Drill. 
 
 Tap. 
 
 Thds 
 
 Drill. 
 
 Tap. 
 
 Thds. 
 
 Drill. 
 
 1 A 
 
 20 
 
 ft in. 
 
 tt 
 
 11 
 
 H 
 
 IK 
 
 7 
 
 ift 
 
 2V* 
 
 4H 
 
 Ifl 
 
 ft 
 
 18 
 16 
 
 X in. 
 15 "- 
 
 3 /4 
 p 
 
 10 
 10 
 
 i 
 
 4 
 
 ivl 
 
 6 
 6 
 
 
 2M 
 23/6 
 
 4'" 
 
 
 ^ 
 
 14 
 
 S2 in> 
 
 
 9 
 
 ,; 
 
 i 
 
 i^l 
 
 53/> 
 
 Iff 
 
 
 4 
 
 2ft 
 
 
 13 
 
 Jito. 
 
 u 
 
 9 
 
 
 i 
 
 1% 
 
 5 
 
 1 Mj 
 
 
 
 
 & 
 
 12 
 
 Bin. 
 
 1 
 
 8 
 
 
 4 
 
 i j/g 
 
 5 
 
 15/ 
 
 
 
 
 5/8 
 
 11 
 
 if in. 
 
 IK 
 
 7 
 
 
 i 
 
 2 , 
 
 4^ 
 
 Iff 
 
 
 
 
 Collar-Screw 
 
 | 1/8 
 
 3/16 
 
 1/4 | 5/16] 3/8 | 7/16 
 
 1/2 | 9/16] 
 
 5/8 | 3/4 
 
 |40 
 
 24 20 
 
 |18 |16 |14 |13 |12 |11 |10 
 
 1/8 
 
 3/16] 
 
 1/4 5/16| 3/8 | 7/16 
 
 3/2 9/16| 
 
 5/8 | 3/4 
 
 11/64 
 
 17/64] 11/32] 7/16] 17/32] 39/64 
 
 11/16] 51/64] 
 
 7/8 | 1-1/16 
 
 | 1/4 
 
 11/32| 7/16] 1/2 | 5/8 | 11/16 
 
 15/16] 15/16|1 | 1-1/4 
 
 1/32 
 
 3/64 
 
 L/16 5/64] 3/32| 7/64 1 
 
 1/8 9/64] 
 
 5/32] 3/16 
 
 Pipe Threads 
 
 Diam. || 
 
 Thds. Per In. 
 
 Diam. Drill || Diam. 
 
 Thds. Per In. 
 
 Diam. Drill 
 
 1/8 || 
 
 27 
 
 | 21/64 || 1-1/4 
 
 11-1/2 
 
 1-15/32 
 
 1/4 || 
 
 18 
 
 29/64 || 1-1/2 
 
 11-1/2 
 
 1-23/32 
 
 3/8 || 
 
 18 
 
 | 19/32 || 2 
 
 11-1/2 
 
 2- 3/16 
 
 1/2 || 
 
 14 
 
 23/32 || 2-1/2 | 8 
 
 2-11/16 
 
 3/4 || 
 
 14 
 
 | 15/16 || 3 
 
 8 
 
 3- 5/16 
 
 1 ' II 
 
 11-1/2 
 
 | 1-3/16 || 3-1/2 
 
 8 
 
 3-13/16 
 
 Standard taper of pipe threads is, 1 inch in 16, or 3/4 inch to 1 foot 
 
180 
 
 MECHANICAL DRAFTING. 
 
 DECIMAL EQUIVALENTS 
 
 Of 8ths, 16ths, 32nds and 64ths of an inch 
 
 8ths. 
 
 ^ = .15625 
 
 if = .234375 
 
 
 & = .21875 
 
 iJ = .265625 
 
 Ys = .125 
 
 j& = .28125 
 
 if = .296875 
 
 M = .250 
 
 M = -34375 
 
 SJ = .328125 
 
 ^ = .375 
 
 if = .40625 
 
 $i = .359375 
 
 1 A = -500 
 
 Ji = .46875 
 
 ff = .390625 
 
 Yz = .625 
 
 JJ = .53125 
 
 } = .421875 
 
 % = .750 
 
 4f = .59375 
 
 |f = .453125 
 
 % = -875 
 
 i = .65625 
 
 fi = .484375 
 
 
 | = .71875 
 
 SI = .515625 
 
 16ths. 
 
 f = .78125 
 
 if = .546875 
 
 
 3 = .84375 
 
 fj = .578125 
 
 A = -0625 
 
 $ = .90625 
 
 ff = .609375 
 
 A = .1875 
 
 4 = .96875 
 
 & = .640625 
 
 & = .3125 
 
 
 jf = .671875 
 
 ft = .4375 
 
 
 ff = .703125 
 
 & = .5625 
 
 64ths. 
 
 U = .734375 
 
 ft = .6875 
 
 
 ff = .765625 
 
 tJ = .8125 
 
 ^ = .015625 
 
 fj = .796875 
 
 tt = .9375 
 
 ^ = .046875 
 
 fi = .828125 
 
 
 ^ = .078125 
 
 M = .859375 
 
 32ds., 
 
 ft = .109375 
 
 |j = .890625 
 
 
 ^ = .140625 
 
 ff = .921875 
 
 & = .03125 
 
 JJ = .171875 
 
 fj = .953125 
 
 = .09375 
 
 JJ = .203125 
 
 M = .984375 
 
APPENDIX. 
 
 181 
 
 SIZES OF NUMBERS OF THE U. S. STANDARD GAGE 
 
 Number 
 of Gage. 
 
 Approximate 
 Thickness in 
 Fractions of 
 an Inch. 
 
 Approximate 
 Thickness in Decimal 
 Parts of an Inch. 
 
 Weight per 
 Square Foot 
 in Ounces. 
 Avoirdupois. 
 
 Weight per 
 Square Foot 
 in Pounds. 
 Avoirdupois. 
 
 16 
 
 A 
 
 .0625 
 
 40 
 
 2.5 
 
 17 
 
 Tiff 
 
 .05625 
 
 36 
 
 2.25 
 
 18 
 
 & 
 
 .05 
 
 32 
 
 2. 
 
 19 
 
 tb 
 
 .04375 
 
 28 
 
 1.75 
 
 20 
 
 5(5 
 
 .0375 
 
 24 
 
 1.50 
 
 21 
 
 55<T 
 
 .034375 
 
 22 
 
 1.375 
 
 22 
 
 A 
 
 .03125 
 
 20 
 
 1.25 
 
 23 
 
 sis 
 
 .028125 
 
 18 
 
 1.125 
 
 24 
 
 A . 
 
 .025 
 
 16 
 
 1. 
 
 25 
 
 3SO- 
 
 .021875 
 
 14 
 
 .875 
 
 26 
 
 T?> iy 
 
 .01875 
 
 12 
 
 .75 
 
 27 
 
 if? <i 
 
 .0171875 
 
 11 
 
 .6875 
 
 28 
 
 A 
 
 .015625 
 
 10 
 
 .625 
 
 29 
 
 ef<y 
 
 .0140625 
 
 9 
 
 .5625 
 
 30 
 
 1 
 
 IV 
 
 .0125 
 
 8 
 
 .5 
 
 31 
 
 1 
 
 .0109375 
 
 7 
 
 .4375 
 
 32 
 
 Tsl<j 
 
 .01015625 
 
 6J/ 
 
 .40625 
 
 33 
 
 TT<I 
 
 .009375 
 
 6 
 
 .375 
 
 34 
 
 T^STy 
 
 .00859375 
 
 "51^ 
 
 .34375 
 
 35 
 
 fffo- 
 
 .0078125 
 
 5 
 
 .3125 
 
 36 
 
 TsW 
 
 .00703125 
 
 4MS 
 
 .28125 
 
 37 
 
 sis<j 
 
 .006640625 
 
 4 M 
 
 .265625 
 
 38 
 
 yJir 
 
 .00625 
 
 4 
 
 .25 
 
182 
 
 MECHANICAL DRAFTING. 
 
 DIFFERENT STANDARDS FOR WIRE GAGE. 
 
 
 
 
 . en 
 
 
 
 "O 
 
 
 
 
 
 ., 03 
 
 
 
 
 
 ^ 
 
 rt 
 
 5 CJ 
 
 
 -& 
 
 <U 
 
 ~ 4J 
 
 o & 
 
 u *S 
 
 
 JS > 
 
 5 % . 
 
 .2 
 
 * ^ 
 
 C -*-* 
 
 U , H 
 
 ^ ^ 
 
 *g > p, 
 
 60 & 
 
 P M CU 
 
 
 _a ** 
 
 ^ . , 
 
 QJ W 
 
 1 
 
 s|l 
 
 i s ]s 
 
 J3 o 
 
 co a o 
 
 u 
 
 || 
 
 V} PH 
 
 C/3 O 
 
 S 
 
 1? 
 
 6 
 
 .is 3 
 c/j 
 
 Cl tU IH 
 
 j 
 
 -1 
 
 
 
 ** 
 
 000000 
 
 
 
 
 .464 
 
 
 46875 
 
 00000(1 
 
 00000 
 
 
 
 
 432 
 
 " 
 
 4375 
 
 UUUUUvf 
 
 OOOOO 
 
 0000 
 
 .46 
 
 .454 
 
 .3938 
 
 .400 
 
 
 .40625 
 
 U \J \J \J U 
 
 0000 
 
 000 
 
 .40964 
 
 .425 
 
 .3625 
 
 .372 
 
 
 .375 
 
 000 
 
 00 
 
 .3648 
 
 .38 
 
 .3310 
 
 .348 
 
 
 .34375 
 
 00 
 
 
 
 .32486 
 
 .34 
 
 .3065 
 
 .324 
 
 
 .3125 
 
 
 
 1 
 
 .2893 
 
 .3 
 
 .2830 
 
 .300 
 
 ."227 
 
 .28125 
 
 1 
 
 2 
 
 .25763 
 
 .284 
 
 .2625 
 
 .276 
 
 .219 
 
 .265625 
 
 2 
 
 3 
 
 .22942 
 
 .259 
 
 .2437 
 
 .252 
 
 .212 
 
 .25 
 
 3 
 
 4 
 
 .20431 
 
 .238 
 
 .2253 
 
 .232 
 
 .207 
 
 .234375 
 
 4 
 
 5 
 
 .18194 
 
 .22 
 
 .2070 
 
 .212 
 
 .204 
 
 .21875 
 
 5 
 
 6 
 
 .16202 
 
 .203 
 
 .1920 
 
 .192 
 
 .201 
 
 .203125 
 
 6 
 
 7 
 
 .14428 
 
 .18 
 
 .1770 
 
 .176 
 
 .199 
 
 .1875 
 
 7 
 
 8 
 
 .12849 
 
 .165 
 
 .1620 
 
 .160 
 
 .197 
 
 .171875 
 
 8 
 
 9 
 
 .11443 
 
 .148 
 
 .1483 
 
 .144 
 
 .194 
 
 .15625 
 
 9 
 
 10 
 
 .10189 
 
 .134 
 
 .1350 
 
 .128 
 
 .191 
 
 .140625 
 
 10 
 
 11 
 
 .090742 
 
 .12 
 
 .1205 
 
 .116 
 
 .188 
 
 .125 
 
 11 
 
 12 
 
 .080808 
 
 .109 
 
 .1055 
 
 .104 
 
 .185 
 
 .109375 
 
 12 
 
 13 
 
 .071961 
 
 .095 
 
 .0915 
 
 .092 
 
 .182 
 
 .09375 
 
 13 
 
 14 
 
 .064084 
 
 .083 
 
 .0800 
 
 .080 
 
 .180 
 
 .078125 
 
 14 
 
 15 
 
 .057068 
 
 .072 
 
 .0720 
 
 .072 
 
 .178 
 
 .0708125 
 
 15 
 
 16 
 
 .05082 
 
 .065 
 
 .0625 
 
 .064 
 
 .175 
 
 .0625 
 
 16 
 
 17 
 
 .045257 
 
 .058 
 
 .0540 
 
 .056 
 
 .172 
 
 .05625 
 
 17 
 
 18 
 
 .040303 
 
 .049 
 
 .0475 
 
 .048 
 
 .168 
 
 .05 
 
 18 
 
 19 
 
 .03589 
 
 .042 
 
 .0410 
 
 .040 
 
 .164 
 
 .04375 
 
 19 
 
 20 
 
 .031961 
 
 .035 
 
 .0348 
 
 .036 
 
 .161 
 
 .0375 
 
 20 
 
 21 
 
 .028462 
 
 .032 
 
 .03175 
 
 .032 
 
 .157 
 
 .034375 
 
 21 
 
 22 
 
 .025347 
 
 .028 
 
 .0286 
 
 .028 
 
 .155 
 
 .03125 
 
 22 
 
 23 
 
 .022571 
 
 .025, 
 
 .0258 
 
 .024 
 
 .153 
 
 .028125 
 
 23 
 
 24 
 
 .0201 
 
 .022 
 
 :0230 
 
 .022 
 
 .151 
 
 .025 
 
 24 
 
 25 
 
 .0179 
 
 .02 
 
 .0204 
 
 .020 
 
 .148 
 
 .021875 
 
 25 
 
 26 
 
 .01594 
 
 .018 
 
 .0181 
 
 .018 
 
 .146 
 
 .01875 
 
 26 
 
 27 
 
 .014195 
 
 .016 
 
 .0173 
 
 .0164 
 
 .143 
 
 .0171875 
 
 27 
 
 28 
 
 .012641 
 
 .014 
 
 .0162 
 
 .0149 
 
 .139 
 
 .015625 
 
 28 
 
 29 
 
 .011257 
 
 .013 
 
 .0150 
 
 .0136 
 
 .134 
 
 .0140625 
 
 29 
 
 30 
 
 .010025 
 
 .012 
 
 .0140 
 
 .0124 
 
 .127 
 
 .0125 
 
 30 
 
 31 
 
 .008928 
 
 .01 
 
 .0132 
 
 .0116 
 
 .120 
 
 .0109375 
 
 31 
 
 32 
 
 00795 
 
 .009 
 
 .0128 
 
 .0108 
 
 .115 
 
 .01015625 
 
 32 
 
 33 
 
 .00708 
 
 .008 
 
 .0118 
 
 .0100 
 
 .112 
 
 .009375. 
 
 33 
 
 34 
 
 .006304 
 
 .007 
 
 .0104 
 
 .0092 
 
 .110 
 
 .00859375 
 
 34 
 
 35 
 
 005614 
 
 .005 
 
 .0095 
 
 .0084 
 
 .108 
 
 .0078125 
 
 35 
 
 36 
 
 .005 
 
 .004 
 
 .0090 
 
 .0076 
 
 .106 
 
 .00703125 
 
 36 
 
 37 
 
 004453 
 
 
 
 .0068 
 
 .103 
 
 .006640625 
 
 37 
 
 38 
 
 .003965 
 
 
 
 .0060 
 
 .101 
 
 .00625 
 
 38 
 
 
 003531 
 
 
 
 0052 
 
 099 
 
 
 39 
 
 40 
 
 ^003144 
 
 
 
 .0048 
 
 .097 
 
 
 40 
 
APPENDIX. 183 
 
 GEOMETRICAL CONSTRUCTIONS 
 THE ELLIPSE 
 
 Definition: An ellipse is a curve generated by the 
 motion of a point ivhich moves so that the sum of its dis- 
 tances from two fixed points is constant. For example, 
 in Fig. 1, the sum, x + y, of the distances from any point 
 on the ellipse to the two fixed points, F a and F 2 is con- 
 stant and equal to 2a. 
 
 Besides being considered a mathematical curve gen- 
 erated according to a certain law, the ellipse may be 
 considered the curve which is cut from the surface of a 
 right circular cone by a plane which intersects all of the 
 elements and is oblique to the axis. Also as the ortho- 
 graphic projection of a circle which is oblique to the 
 plane of projection. 
 
 The long diameter of the ellipse is known as the 
 major axis and the short diameter as the minor axis; in 
 analytic geometry these axes are given values of 2a and 
 26, Fig. 1. 
 
 Construction. The ellipse figures so prominently in 
 drafting that it will be well to give several methods of 
 construction, both exact and approximate. 
 
 Exact Method. (1) From the law according to 
 which the curve is generated it has been found possible 
 to construct the ellipse accurately as follows. With 
 point 0, Fig. 2, as a center and the axes as diameters, 
 describe two circles. Then from draw any number of 
 radii of the large circle, e. g., OA, OB, 00, OD, etc. 
 The vertices a, b, c, d, etc., of the right angles of the 
 right triangles, Aaa^ Bbb ly etc., are points of the required 
 ellipse and the curve may be traced thru these points 
 either freehand or by means of a universal curve. 
 
184 
 
 MECHANICAL DRAFTING. 
 
 Fig. 2 
 
 Fig. 3 
 
APPENDIX. 
 
 185 
 
 Fig. 5 
 
186 MECHANICAL DRAFTING. 
 
 Exact method (2) Trammel method. If from any 
 point P, Fig. 3, on the edge of a -strip of paper or 
 ruler the semi minor and semi major axes he measured 
 to points b and a, and this strip or ruler placed over the 
 axes and moved so that point b is always on the major 
 axis and a on the minor axis, the successive positions of 
 point P are points of the required ellipse. These posi- 
 tions of point P may be marked with a pencil or needle 
 point and the ellipse traced thru them. 
 
 Approximate method (1) 4 center method. Con- 
 nect point B, Fig. 4, with point A. Then with as a 
 center and OB as a radius describe the arc cutting OA 
 at C; lay off from B, on BA, the distance CA, to Cj. 
 The perpendicular bisector of dA locates two of the 
 desired centers and the curve may be drawn with the 
 compass as shown. 
 
 Approximate method (2) 8 center method. Con- 
 struction. Connect points A and B and draw the lines 
 AE and BE, Fig. 5. Then describe the quadrant EC 
 and erect the perpendicular CD. From point in which 
 CD intersects AB draw OE. The arc EF locates center 
 No. 1. EF produced locates center No. 3 at K. Con- 
 nect D and K and produce EF to J; with G and H as 
 centers and GJ as a radius describe arcs intersecting at 
 center No. 2. Centers, 4, 6, and 8 may then be located 
 from 2. It will be noted that center No. 2 does not lie 
 on the radius GK; however, it is so small a distance 
 from GK that no irregularity can be detected in the 
 curves at G. 
 
APPENDIX. 
 
 THE PARABOLA AND HYPERBOLA 
 
 187 
 
 FP-CP' 
 
 O12345678 9 
 
 ! Parabola 
 
 Fig. 6 
 
188 
 
 Parallel 
 
 MECHANICAL DRAFTING. 
 TANGENT CURVES WITH GIVEN RADIUS "r" 
 Parallel 
 
 Parallel 
 
 Tangent to Two Straight Lines 
 Parallel 
 
 Concentric 
 
 Through a Point and Tangent to a Straight Line Through a Point and Tangent to a Curve 
 
 INTERSECTIONS 
 
 Tangent to Straight Line and Curve 
 
 . 7 
 
APPENDIX. 
 
 189 
 
 CONVENTIONAL REPRESENTATIONS. 
 
 Rope 
 
 T^) 
 
 ~ r.iZZ r vJ 
 
 Chain 
 
 Wood 
 
 
 Pipe 
 
 
 Shaft 
 
 Shaft 
 
 Rectangular Bar 
 
 Fig. 8 
 
190 
 
 MECHANICAL DRAFTING. 
 CONVENTIONAL EEPEESENTATIONS (Cont'd) 
 
 Angle 
 
 T-Bar 
 
 I-Beam 
 
 ^^^ 
 
 ^ 
 
 
 
 y 
 
 
 
 y 
 
 
 
 % 
 
 
 
 y. 
 
 
 
 | 
 
 
 
 ? 
 
 
 /777777/y, 
 
 I 
 
 
 Chaniuel 
 
 Z-Bar 
 
 
 fTTTTT/s 
 
 ' 
 
 / 
 
 2 
 
 Y77777?\ 
 
 
 
 
 H-Bar 
 Pig. 
 
APPENDIX. 191 
 
 STANDARD SYMBOLS ADOPTED BY THE 
 NATIONAL CONTRACTORS' ASSOCIA- 
 TION AND THE AMERICAN INSTI- 
 TUTE OF ARCHITECTS. 
 
 Ceiling outlet; electric only. Numeral in center indicates 
 number of standard 16 c-p incandescent lamps. 
 
 Ceiling "outlet; combination. 4/2 indicates 4-16 c-p standard 
 incandescent lamps and 2 gas burners. If gas only 
 
 Bracket outlet; electric only. Numeral -in center indicates 
 number of standard 16 c-p incandescent lamps. 
 
 -- Bracket outlet ; combination. 4/2 indicates 4-16 c-p standard 
 incandescent lamps and 2 gas burners. If gas only 
 
 Wall or baseboard receptacle outlet. Numeral in center 
 of standard 16 c-p incandescent lamps. 
 
 Floor outlet. Numeral in center indicates number of 
 Standard 16 c-p incandescent lamps. - 
 
 Outlet for outdoor standard or pedestal electric only. Numeral 
 indicates number of standard 16 c-p incandescent lamps. 
 
 Outlet for 'outdoor standard or pedestal; combination. 6/3 
 indicates 6 16 c-p. standard incandescent lamps ; 3 gas burners. 
 
 Drop cord outlet. 
 
 One-lamp outlet, for lamp receptacle. 
 
 Arc lamp outlet. 
 
 Special outlet, for lighting, heating and power-current, 
 described in specifications. 
 
192 MECHANICAL DRAFTING. 
 
 ELECTRICAL SYMBOLS (Cont'd) 
 
 Ceiling fan outlet 
 Distribution, panel. 
 Junction or pul] box. 
 
 Motor outlet. 
 Motor control outlet. 
 
 Transformer. 
 
 Main or feeder run concealed under floor. 
 Main or feeder run concealed under floor above. 
 Main or feeder run exposed. 
 Branch circuit run concealed under floor. 
 Branch circuit run concealed under floor. above. 
 Branch circuit run exposed. 
 
 - * Pole line. 
 
 Riser. 
 
 Telephone outlet; private service. 
 ^ Telephone outlet ; public service. 
 
 Q Bell outlet. 
 
 j I, Buzzer outlet. 
 
 r^i g Push button outlet. Numeral indicates. number or pushes.. 
 
 ygv Annunciator. Numeral indicates number of points. 
 
 A Speaking tube. 
 
niHil 
 
 B 
 
 APPENDIX. 193 
 
 ELECTEICAL SYMBOLS (Cont'd) 
 Watchman clock outlet. 
 
 Watchman station outlet. 
 
 Master time clock outlet. 
 Secondary time clock outlet. 
 
 Door opener. 
 
 Special outlet for signal systems, 
 as described in specifications. 
 
 Battery outlet. 
 
 Circuit for clock, telephone, bell or other service, run undeV 
 floor, concealed. Kind of service wanted ascertained by symbol 
 to which line connects. 
 
 Circuit for clock, telephone, bell or other service, run under 
 floor above, concealed. Kind of service wanted ascertained by 
 symbol to which line connects. Meter outlet. 
 
 Meter outlet. 
 
194 
 
 MECHANICAL DRAFTING. 
 
 SYMBOLS USED IN REPRESENTING ELEC- 
 TRICAL AND AUTOMOBILE 
 CONSTRUCTION. 
 
 HHHHHH 
 
 Storage Battery 
 
 D. C. Generator Armature. and Brushes 
 
 Head Light Side Light 
 
 Tail, Dash or Instrument Light 
 
 Electric Horn 
 
 Motor Armature and Brushes 
 
 Coil Size and Weight According to Use 
 
 Ground 
 
 Ammeter Voltmeter 
 
 Condenser 
 
 vwvwv 
 
 Resistance 
 
 Condenser Circuit 
 
APPENDIX. 
 
 195 
 
 ELECTRICAL SYMBOLS (Cont'd) 
 
 A. C. Generator 
 
 
 Wattmeter Circuit 
 
 Motor Starting Circuit (Power) 
 
 I, 
 
 O 
 
 o 
 
 O 
 
 I 
 
 Iron Cored Inductance 
 
196 
 
 MECHANICAL DRAFTING 
 
 CONVENTIONS USED IN HYDROGRAPH 
 
 ICAL AND TOPOGRAPHICAL 
 
 DRAWING. 
 
 Streams 
 
 Lakes and Ponds 
 
 Fresh 
 
 Falls and Rapids 
 
 Fresh and Salt Marsh 
 
 Salt 
 
 Tidal Flats 
 
 Water Lines 
 
APPENDIX 
 
 197 
 
 TOPOGRAPHICAL CONVENTIONS (ContM) 
 
 Contours 
 
 Depression Contours 
 
 Cliffs (Hachured) 
 
198 
 
 MECHANICAL DRAFTING. 
 
 TOPOGBAPHICAL CONVENTIONS (Cont'd) 
 
 ; * ^ii%2* r 1 -'- 
 
 *^ . J& *j&. f .* A*< ^a^* 
 
 Deciduous Trees (Oak) 
 
 
 Deciduous Trees (Round Leaf) 
 
 . 
 
 .* ' . * 
 
 Evergreen Trees 
 
 Orchard 
 
 a 
 
 Clearing 
 
 Grass 
 
 Cultivated Land 
 
 Pasture 
 
APPENDIX. 
 
 199 
 
 -X X- 
 
 + + -I- + 
 
 TOPOGRAPHICAL CONVENTIONS (ContM) 
 
 Bridges 
 Dams 
 
 Board Fence 
 WireJEence 
 Rail Fence 
 Hedge 
 Stone Wall 
 
 Buildings (Large Scale) 
 Buildings (Small Scale) 
 Bench Marks 
 Traverse Stations 
 Stadia Stations 
 
 Triangulation Stations 
 
 B. M. x 1143 
 
 O 
 Q 
 
200 MECHANICAL DRAFTING 
 
 TOPOGRAPHICAL CONVENTIONS (Cont'd) 
 Canals and Ditches 
 
 Tunnels 
 
 Double Track 
 
 Railroads Two Lines 
 
 Electric 
 
 In Road or Street 
 
 Metaled 
 
 Wagon Roads 
 
 Poor or Private 
 
 (Blue) 
 Aqueducts and Water Pipes 
 
 (Blue) 
 Single Track- - I I I | 
 
 Paths or Trails 
 
 (Blue) 
 
 Locks 
 
APPENDIX 
 
 201 
 
 CONVENTIONAL REPRESENTATION OF 
 RIVETS. 
 
 SHOP 
 
 RIVETS 
 
 
 FAR 
 SIDE 
 
 NEAR 
 SIDE 
 
 BOTH 
 SIDES 
 
 Two Full Heads 
 
 
 
 
 
 Countersunk and Chipped 
 
 
 
 XX 
 
 & 
 
 Countersunk and not Chipped 
 
 G> 
 
 tx 
 
 ^s 
 
 Flattened to 1 4 
 
 High 
 
 
 
 
 5 
 
 ^^ 
 
 Flattened to 3 8 
 
 High 
 
 
 O 
 
 t^ 
 
 * 
 
 FIELD 
 
 RIVETS 
 
 
 
 
 
 Two Full Heads 
 
 
 
 
 
 Countersunk and Chipped 
 
 i 
 
 
 
 % 
 
 
 ^. 
 
 f ' x 
 
 SI 
 
 ^ 
 
 'ANDARD RIVET 
 
 t 
 
 HEADS 
 
 i *Nt 
 
 ' 
 
 ^ 
 
 
 
 % ^5|CVi\ 
 
 / 
 
 R( 
 
 <- 
 
 ( 
 
 
 
 
 
 1 
 
 CONE HEAD 
 
 +--^'-+\ 
 Q 
 
 M^T. 
 
 COUNTERSUNK HEAD 
 
 * r*"-| 
 
 )UND HEAr 
 
 Z^j 
 
 s 
 
 ^ 
 
 ^***^ 
 
 mt S}! 1 ^ 
 
 *Hft *i 
 
 Y t 
 
 
 H3\ 
 
 
 7 
 
 
 
 3 
 
 
 \ A 
 
 hiiH 
 
 1 ^ 
 
 
 C 
 
 
 2*1 
 
 
 2 i 
 
202 
 
 MECHANICAL DRAFTING. 
 
 REPRESENTATION OF RIVETS (Cont'd) 
 
 
 
 <,* of fc,;/ 
 
 
 
 9 .1. P,|, 3jc ^-3.3 ^ 
 
 QtfAl.thisencto 
 G/on/y 
 
 61 
 
 /-sc 
 
 ** 
 
 Jife diagram for /ocation 
 
 \Holesthif end G/ Plates pb-P/Z. 
 
 Remainder of Bottom F/ange -same as Tqcr 
 
 except a// fie/J ho/es not 
 
 fo the s/jc/o r/ve/ec/ 
 
 Sfofs other -eno 'O2 Pfotespc-P/3 
 
APPENDIX. 
 
 203 
 
 SINGLE LINE CONVENTIONAL SYMBOLS 
 COMMONLY USED IN MAKING PRELIM- 
 INARY LAY-OUTS, SMALL SCALE 
 DRAWINGS AND SKETCHES 
 OF PIPE SYSTEMS WITH 
 FITTINGS AND AC- 
 CESSORIES. 
 
 Steam Main 
 
 Flanges (Bolted) 
 
 Hot Water Main (Flow) 
 
 o 
 
 Risers 
 
 Air Line 
 
 J 
 
 Tee and Ell, Long Sweep (Same Plane) D rop 
 
 Tee and Ell. Close rSame Plane) 
 
 to 
 
 Rise 
 
 1 1 _i_i 
 
 ^-*' J 1 pYoi-i^.lirto + ol-/v- li*s\wvi TVnvx rtf Hfi 
 
 Branches taken from Bottom of Main 
 
 
 Check Valve 
 
 Globe and Gate Valve 
 
 oL 
 
 t- 
 
 Base Elbow 
 
 Jo 
 
 Radiator Two Pipe Plan 
 Retum Main, Steam and Water 
 
 ft 
 
 Unions ( Screwed ) 
 
 Heat and Vent. Flues, with Registers 
 
204 
 
 MECHANICAL DRAFTING. 
 
 LAYOUTS OP PIPE SYSTEMS (Cont'd) 
 
 Air Valve f 
 
 Radiator 
 
 Jiishing 
 Union 
 ingle Valve 
 
 ^L 
 
 V Bushing 
 Radiator 
 
 Bushing .^. 
 
 T & X 
 
 Ij 
 Union. -r\ 
 
 ,S||, ,0 
 
 
 1 'II 1 'Y 
 
 / \ 
 
 / \ 
 
 Radiator-one pipe-Steam 
 
 1 
 
 Smoke 
 
 A 
 
 Drop and Air Valve< 
 
 A- 
 
 ___ 
 
 \ a ^ Bl 
 fp xH^ 
 k j- 
 
 f' N 
 
 (f 
 
 1! 
 
 1 
 
 Cast Iron Bqiler- 
 
 
 S / 
 
 
 \ 
 1 
 1 
 1 
 
 \-r 
 
 
 
 G h 
 
 I 
 
 
 1 
 
 
 
 
 
 
 Plan 
 7 Sections - and Connections ~ 
 
 s 
 
 Riser 
 
 : 50* D.P 
 
 Branch. 
 
 Steam Main 
 
APPENDIX. 
 
 205 
 
 WIDELY USED SYMBOLS FOR REPRESENT- 
 ING PIPE FITTINGS ON ELABORATE 
 DRAWINGS. 
 
 =wt= 
 
 Large 
 
 Small 
 
 Tee 
 
 EH 
 
206 
 
 MECHANICAL DRAFTING. 
 
 PIPE LAYOUT SHOWN IN ISOMETRIC 
 
APPENDIX. 
 
 207 
 
 SYMBOLS REPRESENTING AIR PIPES IN 
 HEATING AND VENTILATING. 
 
 Dampers Elevation and Plan 
 
 Rectangular Ducts 
 
 Deflecting and Mixing Dampers 
 
 Four Piece 
 
 Elbows in.Round Ducts 
 
208 MECHANICAL DRAFTING. 
 
 INFORMATION FOR INVENTORS 
 
 Note. To those interested in securing patents per- 
 haps the best advice is that they write the Commissioner 
 of Patents at Washington, D. C., for a copy of the " Rules 
 of Practice in the United States Patent Office. " It may 
 be well, however, to give here a few suggestions concern- 
 ing the proper procedure in making application for a 
 patent. 
 
 Records and Preliminary Search. Since patents are 
 occasionally contested on the point of date of conception 
 of the idea, it is well to secure the seal of a notary public 
 on a drawing, sketch or written description of any orig- 
 inal device or improvement without delay. Then for a 
 fee of ten dollars a search of the patent office files will be 
 made by any patent attorney and prints and descriptions 
 furnished of all similar devices on which patents have 
 been granted. In arranging for such a preliminary 
 search, the patent attorney should be supplied with the 
 best possible sketch or drawing and description. 
 
 Patent Application. If in the opinion of the attor- 
 ney consulted it seems possible to secure a patent he will, 
 on instruction, make up the application in the form re- 
 quired by the patent office and containing the following : 
 
 (1) Preamble stating the name and residence of the 
 
 applicant and the title of the invention. 
 
 (2) General statement of the object and nature of 
 
 the invention. 
 
 (3) Brief description of the several views of the 
 
 drawings (if the invention admits of such 
 illustration). 
 
APPENDIX. 209 
 
 (4) Detailed description. 
 
 (5) Claim or claims. 
 
 (6) Signature of inventor. 
 
 (7) Signature of two witnesses. 
 
 Drawings. The drawing submitted with a patent 
 application must be what is commonly termed a descrip- 
 tive assembly. A definite size is specified, and in the 
 "Bules of Practice" supplied by the patent office are 
 given typical drawings and sheets of symbols, conven- 
 tions, etc., to be followed by the draftsman; see accom- 
 panying sheets for copies of these. 
 
210 MECHANICAL DRAFTING. 
 
 TYPICAL PATENT OFFICE DRAWING 
 
 THE SIZE OF THE SHEET MUST BE EXACTLY 
 10 x 15 INCHES. 
 
 THIS SPACE MUST BET EIGHT INCHES' 
 
APPENDIX. 
 
 PATENT OFFICE CONVENTIONS 
 
 USQOO Oft MlfAL 
 
 CA fi&ON 
 
 tov 
 
 ~ 
 
 '/OAT Of 
 
 f 
 
 f 4 ante 
 
 COLOfiS 
 
 YfiiOIV 
 
 ABCDEFGHIJKLMNOPQRSTUVWXYZ 
 &LmsTLopqr 
 
 1Z34.36739O 
 
212 
 
 MECHANICAL DRAFTING. 
 
 PATENT OFFICE ELECTRICAL SYMBOLS 
 
 CROSSING AMD 
 J01NCD 
 
 _L_L 
 
 2. 
 
 GROSSING ANO 
 
 3. 
 
 fr 
 
 . 
 
 9. 
 
 /o. 
 
 12. 
 
 -4WVWV- 
 
 "innnnr 
 
 MI i<y 
 
 /*. 
 
 / 
 XES/STAMCE' 
 
 /7 
 
 2O. 
 
 ruse 
 
 GAOUN 
 
 ir B*e*ir 
 
 fMOfftLOAD) 
 
 27. 
 
 TrfpL 
 
 <4.C. Sft.AY 
 
 29. 
 
 30. 
 
 J/ 
 
 36. *or 
 
 hi N 
 
 37 
 
 36. 
 
 WATTHOtSR 
 
 
 42. 
 
 If 
 
 1 
 
APPENDIX. 
 
 213 
 
 ELECTRICAL SYMBOLS (Con't) 
 
 AV0/OW 
 \'< 
 
 +6 
 
 -3J. 
 
 -O- 
 
 36. 
 
 6O 
 
 RE 
 
 /. 
 
 Qt/ 
 J/'A 
 
 63. 
 
 60. 
 
 If 
 
 of.coMMcwro* oa.i 
 
 tlCroff6A6fNt#ATOA MOTOR 
 fSfHfH*O</M6) fjMV 
 
 
 
 73. 
 
 Q 
 
214 
 
 MECHANICAL DRAFTING. 
 
 METHODS OF REPRESENTING 
 FACTS GRAPHICALLY 
 
 HIIIIIIIIIIIBfe:- 
 
APPENDIX. 215 
 
 ALPHABETS. 
 
 ANALPHABET 
 r ARCHITECTS 
 
 rstuvwxuz 1234567 
 Plan, of Second Floor 
 
 A5CDEF(jHIJKLM 
 NOPQ^TUVWYL 
 
 A good alphabet for 
 
 lettering plans &lc. 
 
216 MECHANICAL DRAFTING. 
 
 ALPHABETS (Cont'd) 
 
 ARCHITECTURAL 
 LETTEU DETMJ 
 
 Jmall Lettenr abcdefg 
 hijklinnopqnrtuvwxyz 
 Free aud_yet Claozric in 
 effect and fedind al</o . 
 
 o 
 
 ABCDIFGHI 
 JKLMNOPQ 
 
 LJTUYXWYZ 
 
 -to be \i<fe,d in 
 Jinel-form vliere 
 
APPENDIX. 
 ALPHABETS (Cont'd) 
 
 217 
 
218 
 
 MECHANICAL DRAFTING. 
 ALPHABETS (Cont'd) 
 
APPENDIX. 
 
 GUMMED LETTERS. 
 
 219 
 
 CsjCSl 
 
 >; 
 
220 
 
 MECHANICAL DRAFTING. 
 GUMMED LETTERS (ContM) 
 
 CM 
 
 CM* 
 
APPENDIX 
 
 221 
 
 BILL OF MATERIAL 
 
 No. of 
 Pieces 
 
 Pat tern No. 
 
 Mark 
 
 Material 
 
 Nome 
 
 1 
 
 A J6I 
 
 
 C.I 
 
 Body 
 
 1 
 
 C 41 
 
 
 a 
 
 Stuffing Box 
 
 / 
 
 B 74 
 
 
 a 
 
 Gland 
 
 ^ 
 
 M 60 
 
 
 Brass 
 
 Discs 
 
 / 
 
 D 104 
 
 
 C.I. 
 
 Ha not Wheel 
 
 / 
 
 5 16 
 
 
 Brass 
 
 Stem 
 
 i 
 
 L 76 
 
 
 C.I. 
 
 Gate 
 
 i 
 
 
 
 
 Stud Bolts 
 
 z 
 
 
 
 
 hex. Nuts 
 
 
 
 
 
 
 
 
 
 
 
 STRAIGHT WAY VALVE 
 
 CRANE COMPANY 
 
 Ct-f/CAGO, /L.L.IMO/S 
 
 Nov. ^4 ) /9/6 r~u//5ize 
 
 Note: The title ctncf b/// of material need not be 
 joined together. 
 
INDEX 
 
 [Numbers Refer to Articles] 
 
 Allen set screw, 56. 
 
 Alphabet, Reinhardt, 1. 
 
 Angles, Co-ordinate, 32. 
 
 Anneal, 69. 
 
 Approximate mechanical 
 
 method, in isometric projection, 77. 
 
 Architect's scale, 48. 
 
 Areas, method of, 8. 
 
 Arrangement of details in working draw- 
 ing, 41. 
 
 Assembly drawing, defined, uses, char- 
 acteristics, 40. 
 
 Auxiliary planes of projection, 36. 
 
 B. 
 
 Babbitt, 71. 
 
 Ball pointed pen, 2. 
 
 Banana curve, 25. 
 
 Bearings, 71. 
 
 Bevelled tracing rule, 46. 
 
 Bill of Material, 28. 
 
 Blotters, 22. 
 
 Bolt terms, 55. 
 
 Bolts, construction of, 54. 
 
 Bolts, dimensioning, 55. 
 
 Bolts and nuts, 54. 
 
 Border lines, 15. 
 
 Bore, 64. 
 
 Boring machine, 64. 
 
 Bottles, ink, use, etc., 29. 
 
 Bow dividers, adjustment, etc., 26. 
 
 Bow pencil, use, care, etc., 27. 
 
 Brasses, 71. 
 
 C. 
 
 Carriage bolts, 54. 
 Chamois roll, 22. 
 Characteristic section lines, 44. 
 Chatter braces, 62. 
 Circles, in isometric projection, 77. 
 Circles, in oblique projection, 84 
 Circles, in perspective, 107. 
 Cleaning pads, 22. 
 Cloth, tracing, 45. 
 Compass, large, adjustment, use, 24. 
 
 Compressed style of letters, 3. 
 
 Conventional lines, 47. 
 
 Conventional representation of threads, 53. 
 
 Co-ordinate angles, 32. 
 
 Co-ordinate axes, in oblique projection, 80. 
 
 Co-ordinate planes, 32. 
 
 Co-ordinate planes, in oblique projection, 
 
 80. 
 
 Co-ordinate planes, revolution of, 32. 
 Co-ordinates, in perspective, 105. 
 Core, 66. 
 
 Crest, of threads, defined, 52. 
 Crowding, of letters, 8. 
 Curves, irregular, 25. 
 Cylinders, sectional, 44. 
 
 D. 
 
 Detailed drawing, arrangement of de- 
 tails, 41. 
 
 Detailed drawing, denned, 39. 
 
 Detailed signature, 41. 
 
 Diameter of bolts, 55. 
 
 Dies, 58. 
 
 Dimensioning, in isometric projection, 78. 
 
 Dimensioning, in oblique projection, 81. 
 
 Dimensioning, rules of, 43. 
 
 Direct light, denned, 86. 
 
 Directrices in isometric projection, 73. 
 
 Dividers, bow, adjustment, etc., 26. 
 
 Dividers, large, 23. 
 
 Double threads, denned, 51. 
 
 Drawing board, construction of, 13. 
 
 Drawing board, use, 13. 
 
 Drawing paper, position of on board, 14. 
 
 Drawing paper, proper method of tack- 
 ing, 14. 
 
 Drawing paper, quality, 14. 
 
 Drawing titles, denned, 10. 
 
 Drill, 63. 
 
 Drill press, 63. 
 
 Drive screw, 56. 
 
 Eight point method, in isometric projec- 
 tion, 77. 
 
 222 
 
INDEX 
 
 223 
 
 Elements of freehand letters, 3. 
 End plane, 32. 
 End view, 32. 
 Engineer's scale, 48. 
 Erasers, care of, 21. 
 Extended style of letters, 3. 
 
 F. 
 
 Fasteners, 49. 
 
 Fillet, 70. 
 
 Finish, 61. 
 
 First angle, elimination of, 32. 
 
 Formation of letters, 4. 
 
 Front view, 32. 
 
 O. 
 
 G. E. D. special curve, 25. 
 Gothic alphabet, constructions, 7. 
 Guide for lettering, 2. 
 Guide lines, for lettering, 3. 
 Guide lines, in drawing titles, 11. 
 Gummed letters, Willson's, 12. 
 
 H. 
 
 Harden, shop term, 69. 
 
 Helix, the, 50. 
 
 Hidden lines, projections of, 35. 
 
 Horizon, in perspective, 102. 
 
 Horizontal plane, 32. 
 
 Indirect light, defined, 86. 
 
 Ink bottle, use, etc., 29. 
 
 Inking of pt-ns. proper method, 2. 
 
 Interpolated sections, 44. 
 
 Irregular curves, 25. 
 
 Irregular objects in isometric projection, 
 
 76. 
 Irregular objects, in oblique projection, 
 
 85. 
 
 Irregular objects, in perspective, 108. 
 Isometric axes, 73. 
 Isometric construction, 75. 
 Isometric plane, 72. 
 Isometric propection, principles of, 72. 
 Isometric scale, 74. 
 
 Key on flat, 59. 
 
 Keyseat, 59. 
 
 Keys and key ways, 59. 
 
 Lag screws, 56. 
 
 Lead, of threads, denned, 52. 
 
 Length of bolts, 55. 
 
 Lettering pens, 2. 
 
 Letters, freehand, formation of, 4. 
 
 Letters, gummed, 12. 
 
 Line =0= Graph, 30. 
 
 Lines, conventional, 47. 
 
 Lines of sight, in perspective, 97. 
 
 Machine bolts, 54. 
 
 Machine sketch, defined, 88. 
 
 Margins and margin lines, 11. 
 
 Mechanical engineer's scale, 48. 
 
 Mechanical letters, 6. 
 
 Mechanical spacing, 8. 
 
 Mill, 62. 
 
 Milling machine, 62. 
 
 Moore's pen; 2. 
 
 N. 
 
 Name plates, defined, 9. 
 Needle point, construction of, 18. 
 Needle point, from Richter instruments, 
 
 18. 
 
 Normal style of letters, 3. 
 Nuts, 54. 
 
 O. 
 
 Oblique construction, 83. 
 
 Oblique projection, defined, 79. 
 
 Oblique scale, 82. 
 
 Order of inking in tracing, 45. 
 
 Order of pencil work on drawing, 42. 
 
 Order of prominence, in drawing title, 
 11. 
 
 Order of work on details, 41. 
 
 Orthographic projection, defined, 31. 
 
 Orthographic projection, permissible vio- 
 lations of, 34. 
 
 Orthographic projection, principles of, 
 32. 
 
 Orthographic projections, summary of 
 principles, 33. 
 
 Origin, in isometric projections, 72. 
 
 Ovals, element of freehand letters, 3. 
 
 P. 
 
 Paper, drawing, position on board, 14. 
 Paper, drawing, quality, 14. 
 
224 
 
 INDEX. 
 
 Paper, for lettering^ 2. 
 
 Paysan pen, 2. 
 
 Pen, ruling, use, care, etc., 28. 
 
 Pens, lettering, 2. 
 
 Pencil, bow, 27. 
 
 Pencil for sketching, 91. 
 
 Pencil work, order of, 42. 
 
 Pencils, numbering, 20. 
 
 Pencils, sharpening, 20. 
 
 Pencils, use of points, 20. 
 
 Perspective construction, 106. 
 
 Perspective drawing, denned, 96. 
 
 Perspective, principles of construction, 97. 
 
 Picture plane, in perspective, 96. 
 
 Pipe threads, 57. 
 
 Pitch, of threads, defined, 52. 
 
 Planes, co-ordinate, 32. 
 
 Planes, horizontal, vertical, end, 32. 
 
 Planes of projection, 32. 
 
 Planes of projection, auxiliary, 36. 
 
 Point of sight in perspective, 99. 
 
 Point of sight, position of, 109. 
 
 Position of object, in perspective, 103. 
 
 Positions of views in working drawings, 
 
 37. 
 
 Principle point in perspective, 100. 
 Principles of isometric projection, 72. 
 Principles of orthographic projection, 32. 
 Principles of shades and shadows, 86. 
 Profile plane. 32. 
 Projections, 32. 
 
 Projections of hidden lines, 35. 
 Projection, orthographic, defined, 31. 
 Projections of objects, 32. 
 Projections, planes of, 32. 
 Prominence, methods of securing, 11. 
 Prominence, order of, 11. 
 Protractor, use, etc., 51. 
 
 R. 
 
 Raised tracing rule, 46. 
 Ream, 65. 
 Reamer, 65 
 
 Reinhardt alphabet, 1. 
 Revolution of co-ordinate planes, 32. 
 Root, of threads, defined, 52. 
 Round key, 59. 
 Ruling pen, use, care of, etc., 28. 
 
 S. 
 
 Scale, care of, 17. 
 Scale, isometric, 74. 
 Scale, use of, 17. 
 Scale vs. size, defined, 48. 
 
 Scales, defined, 48. 
 
 Scratch paper, method of spacing, 11. 
 
 Screws, defined, 56. 
 
 Sectioning, indication of materials, 44. 
 
 Section lines, 44. 
 
 Sectioning, principles of, 44. 
 
 Square threads, defined, 51. 
 
 Shade and shadow construction, 87. 
 
 Shade, defined, 86. 
 
 Shades and shadows, in isometric and 
 
 oblique projection, 86. 
 Shadow, defined, 86. 
 Sheppard lettering pen, 2. 
 Shop terms, use, 60. 
 Short cuts, in sketching, 94. 
 Shoulder screw, 56. 
 Side view, 32. 
 Signature detail, 41. 
 Single threads, defined, 51. 
 Sketch, size of, 92. 
 Sketch stroke, 91. 
 Sketching, procedure, 93. 
 Sketching, short cuts, 94. 
 Slope guide, 2. 
 Spacing, 8. 
 
 Spacing of letters in titles, 11. 
 Spacing, mechanical, 8. 
 ' Stems, of freehand letters, 3. 
 Straight seated key, 59. 
 Stud bolt, 54. 
 
 T. 
 
 T-Square, construction of, 16. 
 T- Square, proper use, 16. 
 T- Square, to clean, 16. 
 Tap drill, 68. 
 Tap, shop operation, 67. 
 Taps, 58. 
 Temper, 69. 
 Threads, classified, 51. 
 Threads, conventional representation of, 
 
 53. 
 
 Threads, principles of, 50. 
 Threads, terms, 52. 
 Title, drawing construction of, 11. 
 Title, drawing, defined, 10. 
 Top view, 32. 
 Tracing, 45. 
 Tracing rules, 46. 
 Triangles, to clean, 19. 
 Triangles, use, 19. 
 Tripple threads, defined, 51. 
 Twist drills, 63. 
 
INDEX. 
 
 225 
 
 u. 
 
 Unit space, defined, 6. 
 
 V. 
 
 V threads, denned, 51. 
 
 Vanishing point, in perspective, 101. 
 
 Vertical letters, 5. 
 
 Vertical plane, 32. 
 
 Views, orthographic, top, front, and side, 
 32. 
 
 W. 
 
 Weights of lines, in tracing, 45. 
 Working drawings, defined, 38. 
 Working drawings, positions of views, 
 
 37. 
 
 Wood screws, 56. 
 Woodruff key, 59. 
 
 INDEX TO APPENDIX 
 
 [Numbers Refer to Pages] 
 
 Photographic Reproductions Page 
 
 Blue printing 162 
 
 Brown printing 164 
 
 Zinc etching 169 
 
 Wax engraving 171 
 
 Half tones 171 
 
 Abbreviations 173 
 
 Reference tables 175 
 
 Geometrical Constructions 
 
 Ellipse 183 
 
 Parabola and hyperbola 187 
 
 Intersections, tangents 188 
 
 Page 
 
 Conventional representations 189 
 
 Electrical symbols 191, 212 
 
 Topographical conventions 196 
 
 Hydrogaphic conventions 196 
 
 Rivets 201 
 
 Pipe conventions 203 
 
 Patent office regulations, etc 208 
 
 Graphic representation of facts 214 
 
 Alphabets 215 
 
 Gummed letters 219 
 
 Bill of Materials. . . .221 
 
BOOKS ON THE MANUAL ARTS 
 
 * Indicates recent publications and new or revised editions. 
 
 DESIGN AND CONSTRUCTION IN WOOD. By Noyes. A book full of charm 
 and distinction. It illustrates a series of projects and gives suggestions for other 
 similar projects, together with information regarding tools and processes for mak- 
 ing. A pleasing volume abundantly and beautifully illustrated. $1.50. 
 
 HANDWORK IN WOOD. By Noyes. A comprehensive and scholarly treatise, 
 covering logging, saw-milling, seasoning and measuring, hand tools, wood fasten- 
 ings, equipment and care of the shop, the common joints, types of wood structures, 
 principles of joinery, and wood finishing. 304 illustrations excellent pen drawings 
 and many photographs. The best reference book available for teachers of wood- 
 working. $2.25. 
 
 WOOD AND FOREST. By Noyes. A reference book for teachers of wood- 
 working. Treats of wood, distribution of American forests, life of the forest, 
 enemies of the forest, destruction, conservation and uses of the forest, with a key 
 to the common woods by Filibert Roth. Describes 67 principal species of wood 
 with maps of the habitat, leaf drawings, life size photographs and microphoto- 
 graphs of sections. Profusely illustrated. $3.00. 
 
 HANDCRAFT IN WOOD AND METAL. By Hooper and Shirley. A valuable 
 reference book on craftwork in wood and metal. It treats of historic craftwork, 
 materials used in handcrafts, designing, decorative processes, the historic develop- 
 ment of tools, the theory of the cutting action of tools, and the equipment of the 
 school workshop. $3.00. 
 
 *WOOD PATTERN-MAKING. By Purfleld. A clear, concise treatise on the 
 fundamental principles of pattern-making. It presents the best methods of con- 
 struction and those most easily understood by the student. A practical text for 
 high school, trade school, technical school and engineering college students. New 
 edition $1.25. 
 
 ESSENTIALS OF WOODWORKING. By Griffith. A textbook written es- 
 pecially for grammar and high school students. The standard textbook on ele- 
 mentary woodworking. A clear and comprehensive treatment of woodworking tools, 
 materials, and processes, to supplement, but not to take the place of the instruc- 
 tions given by the teacher. The book may be used with any course of models. 
 75 cents. 
 
 CORRELATED COURSES IN WOODWORK AND MECHANICAL DRAWING. 
 By Griffith. Contains reliable information concerning organization of courses, sub- 
 ject matter, and methods of teaching. It covers classification and arrangement of 
 tool operations, stock bills, cost of material, records, shop conduct, the lesson, 
 maintenance, equipment and lesson outlines for grammar and high schools. The 
 most complete and thoro treatment of the subject of teaching woodworking ever pub- 
 lished. $2.00. 
 
 BEGINNING WOODWORK. By VanDeusen. A valuable- textbook for rural 
 schools, by one who has made a special study of the manual training problems in 
 the country school. A full and clear description in detail of the fundamental pro- 
 cesses of elementary benchwork in wood. $1.00. 
 
 *PROJECTS FOR BEGINNING WpODWORK AND MECHANICAL DRAWING. 
 By Griffith. A collection of 50 working drawings and working directions of pro- 
 jects which have proved of exceptional service where woodworking and mechanical 
 drawing are taught in a thoro, systematic manner in the seventh and eighth grades. 
 75 cents. 
 
 * FURNITURE MAKING ADVANCED PROJECTS IN WOODWORK. By 
 Griffith. A collection of problems in furniture making selected and designed with 
 reference to high school use. On the plate with each working drawing is a good 
 perspective sketch of the completed object. In draftsmanship and refinement of 
 design these problems are of superior quality. An excellent collection. 75 cents. 
 
 Published by the MANUAL ARTS PRESS, Peoria, Illinois 
 
 "Books on the Manual Arts," a bibliography free on request. 
 
BOOKS ON THE MANUAL ARTS 
 
 * Indicates recent publications and new or revised editions. 
 
 FURNITURE DESIGN FOR SCHOOLS AND SHOPS. By Crawshaw. A man- 
 ual on furniture design containing a collection of plates showing perspective draw- 
 ings of typical designs, representing particular types of furniture. Each perspec- 
 tive is accompanied by suggestions for rearrangements and the modeling of parts. 
 The text discusses and illustrates principles of design as applied to furniture. 
 Should be in the hands of every teacher of cabinet making and designing. $1.25. 
 
 PROBLEMS IN FURNITURE MAKING. By Crawshaw. Contains 43 full-page 
 working drawings of articles of furniture. In addition to the working drawings, 
 there is a perspective sketch of each article completed. There are 36 pages of text 
 giving notes on the construction of each project, chapters on the "Design," and 
 "Construction" of furniture, and one on "Finishes." The last chapter describes 
 15 methods of wood finishing, all adapted for use on furniture. $1.00. 
 
 PROBLEMS IN WOOD-TURNING. By Crawshaw. Contains 25 full-page plates 
 of working drawings, covering spindle, faceplate, and chuck turning. It gives the 
 mathematical basis for cuts used in turning. A valuable textbook for student's use. 
 80 cents. 
 
 *WORKSHOP NOTE-BOOKWOODWORKING. By Greene. A note-book 
 which furnishes a few general and extremely important directions about tools and 
 processes; and provides space for additional notes and working drawings. It is es- 
 sentially a collection of helps, ideas, hints, suggestions, questions, facts, illustra- 
 tions, etc. The note-book is full of suggestions; sho^s a keen insight into subject 
 matter aud teaching methods and is an effective teaching tool. 19 cents. 
 
 *PROBLEMS IN MECHANICAL DRAWING. By Bennett. A students' text- 
 book consisting of 80 plates of problems classified into groups according to prin- 
 ciple, and arranged according to difficulty of solution. Each problem is given un- 
 solved and therefore in proper form to hand to the pupil for solution. The best 
 collection of problems for first year high school students in book form. New edition 
 75 cents. 
 
 EFFECTIVE METHODS IN MECHANICAL DRAWING. By Evans. A prac- 
 tical textbook of drafting methods. The book deals with "The Geometry of Draft- 
 ing" and "Kinks and Short Cuts," including a simple and practical method of 
 making working drawings of bevel gears. 75 cents. 
 
 THE DRAFTING ROOM SERIES. By Evans. A modern and successful text- 
 book treating of "Reading Machine Drawings," "Machine Drafting," and "Interference 
 of Moving IParts and Tooth Gears." It consists of 54 cards and 3 pamphlets of 
 standard filing card size, 5x8 inches, in a filing box. Rich in content, practical in 
 method and extremely adaptable in form. $2.00. 
 
 SIMPLIFIED MECHANICAL PERSPECTIVE. By Frederick. A textbook of 
 simple problems covering the essentials of mechanical perspective. It is planned 
 for pupils of high school age who have already received some elementary training in 
 mechanical drawing. It is simple, direct and practical. 75 cents. 
 
 PRACTICAL TYPOGRAPHY. By McClellan. A textbook for students of print- 
 ing containing a course of exercises ready to place in the hands of pupils. It ex- 
 plains and illustrates the most approved methods used in correct composition. It 
 contains 63 exercises, treating of composition from "Correct Spacing" to the 
 "Making up of a Book," and the "Composition of Tables." $1.50. 
 
 ART METALWORK. By Payne. A textbook written by an expert craftsman 
 and experienced teacher. It treats of the various materials and their production, 
 ores, alloys, commercial forms, etc. ; of tools and equipments suitable for the work, 
 and of the correlation' of art metalwork with design and other school subjects. It is 
 abundantly and beautifully illustrated. The standard book on the subject. $2.00. 
 
 *SHOP PROBLEMS. (On Tracing Paper) By Siepert. A collection of work- 
 ing drawings of a large variety of projects printed on tracing paper and ready for 
 blue printing. The projects have all been worked out in manual arts classes and have 
 proved their value from the standpoint of design, construction, use, human interest, 
 etc. They are of convenient size 6x9 inches and are enclosed in a portfolio. Pub- 
 lished in sizes No. 1, No. 2, No. 3 and No. 4. Each 35 cents. 
 
 WE CAN SUPPLY ANY BOOK ON THE MANUAL ARTS 
 Published by the MANUAL ARTS PRESS, Peoria, Illinois 
 
 "Books on the Manual Arts," a bibliography free on request. 
 
UNIVERSITY OF CALIFORNIA LIBRARY 
 BERKELEY 
 
 THIS BOOK IS DUE ON THE LAST DATE 
 STAMPED BELOW 
 
 Books not returned on time are subject to a fine of 
 50c per volume after the third day overdue, increasing 
 to $1.00 per volume after the sixth day. Books not in 
 demand may be renewed if application is made before 
 expiration of loan period. 
 
 i 13 I92U 
 
 20 I92J 
 
 SEP 
 
 IMI 7 
 
 1923 
 
 MAR 16) 
 
 REC'D LD 
 
 LIBRARY USE 
 
 FEB 18 1963 
 
 
 LD 
 
 FEB 1 8 1963 
 
 50w-7,'16 
 
YB 15861 
 
 UNIVERSITY OF CALIFORNIA LIBRARY