MECHANICAL DRAWING 
 
 STANDARDS AND 
 CONVENTIONS 
 
 F. R. KEPLER

 
 STANDARDS AND CONVENTIONS
 
 MECHANICAL DRAWING 
 
 BY 
 
 FRANK R. KEPLER 
 
 Cass Technical High School Drafting Department 
 
 Revised by 
 
 DETROIT MANUAL TRAINING CLUB'S 
 STANDARDS COMMITTEE 
 
 Published under Authority of 
 
 THE BOARD OF EDUCATION 
 DETROIT, MICH
 
 Copyright 1916, 
 
 by 
 FRANK R. KEPLER, Chairman 
 
 First Issue .... October 1915 
 First Edition . . . March 1916 
 Second Edition . . . July 1916 
 
 Printed in 
 
 Cass Technical High School 
 Detroit, Michigan
 
 PREFACE TO FIRST EDITION 
 
 A COMMITTEE on STANDARDS AND CONVENTIONS for Mechanical 
 ^~JL Drawing was selected by the Executive Committee of the 
 Detroit Manual Training Club. 
 
 Copies of a preliminary issue of STANDARDS AND CONVEN- 
 TIONS for Cass Technical High were used as a basis of inquiry 
 and criticism. These copies were sent out to fifty representative 
 concerns in Detroit and Michigan. The criticisms of a large major- 
 ity of the representatives of these firms were gathered together, 
 carefully noted, and discussed. Points were finally decided as 
 the consensus of opinion seemed to indicate. School require- 
 ments and good educational methods have governed the decision 
 of points which did not seriously conflict with good industrial 
 practice. 
 
 This first edition is presented with the hope that these 
 STANDARDS AND CONVENTIONS, determined as stated above, will 
 be generally adopted in the schools. 
 
 The chairman takes this opportunity to acknowledge the 
 interest, suggestions, and helpfulness of the various members of 
 the committee. 
 
 Signed 
 
 F. R. KEPLER, CHAIRMAN 
 
 CASS TECHNICAL 
 
 L. G. BURGESS, SEC'Y 
 
 NORTHWESTERN 
 
 P. A. CUMMINS 
 
 CASS TECHNICAL 
 
 EDWARD GATES 
 
 CENTRAL 
 
 JOHN F. GRANT 
 
 EASTERN 
 
 D. W. HICKOK 
 
 WESTERN 
 
 2O65666
 
 PREFACE TO FIRST ISSUE 
 
 THE notes and plates for STANDARDS AND CONVENTIONS have 
 been brought together by Mr. P. A. Cummins and myself for 
 use in Cass Technical High School. They are the result of sev- 
 eral years' experience in teaching Continuation, Evening, and 
 High School classes, and are a study of the requirements of mod- 
 ern drafting room practices. 
 
 Mr. Carnot Iverson, Cass Technical High School, inked in 
 all the drawings for the plates and made the original drawings for 
 Plates 15 and 16. 
 
 Friendly criticisms of our initial copy will be greatly appre- 
 ciated as it is our endeavor to meet the best drafting-room prac- 
 tices. 
 
 FRANK R. KEPLER
 
 PLATE 1 
 
 Page Eiht
 
 GENERAL DIRECTIONS AND NOTES 
 
 DIRECTIONS 
 For Laying Out D-size Sheets 
 
 Place a sheet of drawing paper $y 2 " by 12" upon the 
 drawing board so that the upper edge is in line with the tee- 
 square. Placing the tee-square diagonally across the paper 
 from corner to corner, draw portions of the diagonals near 
 the center to find the exact center of the sheet. Now through 
 he center draw a horizontal and a vertical line across the 
 paper. Measure 4y 2 " above the center and 4y 2 " below the 
 center; through the points thus found draw horizontal lines. 
 These two lines are the cutting lines along which to trim the 
 finished drawing, making the sheet 9" by 12". Again measure 
 5y 2 " to the right and 5y 2 " to the left; through these points 
 draw vertical lines. Next measure 4" above the center along 
 the vertical line and 4" below the center and through these 
 points draw horizontal lines. These four border lines en- 
 close a rectangle 8" by 11". Observe Plate 1.* 
 
 A title block is used in all cases. The title block will ap- 
 pear in the lower right hand corner, arranged as shown in 
 Plate 3. The title block should be penciled in complete before 
 the drawing itself is begun. 
 
 Guide lines in pencil should be drawn for the tops and 
 bottoms of all letters but must not be drawn in ink. 
 
 Each drawing shall first be done in pencil and submitted 
 to the instructor for approval or corrections. The drawing 
 is to be inked when it has been approved by the instructor and 
 he has placed the word "INK" on the margin. 
 
 When the drawing is finished, it shall again be submitted 
 for final approval before the word "INK" is cut off. It shall 
 then be trimmed to the proper size and handed in. 
 
 One plate from each set may be retained as the property 
 of the school. 
 
 *The sheet may be laid out without first finding the center, hut the 
 distance from the upper to the lower cutting lines must be 9" and the 
 border rectangle must be 8" by 11". 
 
 Page Nine
 
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 PLATE 2 
 
 Ten
 
 DIRECTIONS 
 For Laying Out C-size Sheets 
 
 Place the sheet of drawing paper, provided for the pur- 
 pose, on the drawing board so that one of the long sides is 
 even with the upper edge of the T-square. Draw a vertical 
 line y 2 " from the left-hand edge and another 18" to the right 
 of the first. These two lines are the cutting lines along which 
 the sheet is to be trimmed thus removing the thumb-tack 
 holes when the drawing is completed. Leaving 1" margin at 
 the left and y 2 " margin on the other three sides, draw a bor- 
 der rectangle 11" x 16y 2 ". Observe Plate 2. 
 
 Unless otherwise directed, a title block is to be placed in 
 the lower right-hand corner. This title block is to contain 
 the name of the school, the title of the drawing, by whom 
 drawn, by whom traced, and checked as well as approved, and 
 th enumber of the drawing. It is to be spaced and arranged 
 as shown in Plate 3. 
 
 A Bill of Material is generally placed on all drawings for 
 shop purposes arid erecting. This list must contain the num- 
 ber of parts, the material of which they are made, the name 
 of the part, the reference number on the drawing and, if a 
 pattern is required, the pattern letter. (The pattern num- 
 ber consists of the drawing number and the letter; thus, 
 PATT. C-204A). The letters of the Bill of Material are 3/32" 
 high, and the columns are arranged as shown in Plate 4. It 
 may be placed in any convenient space on the drawing but 
 preferably above the title-block. The listing of the parts be- 
 gins at the bottom, a few spaces being left at the top for the 
 listing of additional parts if occasion demands it. Such stan- 
 dard parts as bolts, machine screws, washers, etc., are listed 
 but are NOT DRAWN. 
 
 The cutting-lines, border rectangle, title block, and bill 
 of material must all be arranged properly in pencil before the 
 drawing itself is begun. Be careful to make the drawing ac- 
 curate in pencil, making all corrections before inking any 
 part of the drawing. Do not begin inking until the penciled 
 drawing has been submitted to your instructor for his ap- 
 proval and he has placed the word "Ink" on the margin. 
 
 When the drawing has been carefully inked or traced it 
 must again be submitted to the instructor for his final ap- 
 proval before removing it from the drawing board. This 
 approval secured, the finished drawing is to be trimmed to the 
 required size, 12" x 18", and handed in. 
 
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 Page Thirteen
 
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 Page Fourteen
 
 STANDARDS AND CONVENTIONS 
 
 P. A. Cummins F. R. Kepler. 
 
 The following conventions and standards are to be fol- 
 lowed in making all drawings: 
 
 1. The sizes of drawings shall be 6" x 9", 9" x 12", 
 12" x 18", 18" x 24" and 24" x 36 " and with border lines as indi- 
 cated in Plates 1 and 2. These sizes are chosen for the reason 
 that commercial stock may more readily be cut to these 
 dimensions and the smaller can be cut from the larger without 
 waste. Plate 5. 
 
 2. The letters and figures used for notes and dimensions 
 shall be after the form adopted inclined right line lettering. 
 Plate 6. 
 
 3. All notes on drawings shall be made with capital let- 
 ters 3/32" high, made between light guide-lines that distance 
 apart. 
 
 4. . Figures must be made of the same height. Fractions 
 are to be made higher than the whole numbers and with the 
 division line horizontal. Plate 6. 
 
 5. The conventional lines of the kinds and weights 
 shown are to be used as required to give a contrast between 
 the object and other lines. The beginner often makes his 
 object lines too light. Plate 6. 
 
 6. Arrow heads are always to be made narrow. They 
 must not be large and spread out. Plate 4. 
 
 7. The Title and Bill of Material are to be laid out as 
 shown in Plates 3 and 4. The Bill of Material must contain 
 drawing and, if a pattern is required, the pattern letter or 
 number. It may be placed in any convenient space on the 
 drawing but preferably above the title block. The listing of 
 the parts begins at the bottom, a few spaces being left at the 
 top for the listing of additional parts if occasion demands it. 
 
 8. Each part shall have a Reference Number, whether 
 the part is detailed on the drawing or is a standard part. Each 
 number is to appear on or near the piece if detailed; if stan- 
 dard it is to be placed near where it belongs, an arrow show- 
 ing the exact location. Each number is to be 3/16" high and 
 be placed within a heavy circle %" in diameter, the number 
 being of the same weight. The number should be made first 
 
 Page Fifteen
 
 A B COEFGHIJKLMNOPQRSTU'V 
 
 CONVENTIONAL LINES 
 BORDER L/A/E 
 
 VISIBLE EDGE 
 
 HIDDEN EDGE: 
 
 REFERENCE 
 
 Dl MEMS/ON L./NE 
 CENTER L/NE 
 
 PROJECT/ON L/A/E 
 
 CORRECT 
 
 WRONG 
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 PLATE 6 
 
 Page Sixteen
 
 and then the circle drawn, so that the number will appear in 
 the exact center of the circle. A corresponding number shall 
 appear in the Bill of Material with the name of the part. 
 Plate 4. 
 
 9. The numbering of the drawings shall be on the fol- 
 lowing basis: The size of the sheets shall be designated as 
 A for 24" x 36", B for 18" x 24", C for 12" x 18", D for 9" x 12" 
 and E for 6" x 9". Plate 5. 
 
 Drawings in the first year shall be numbered from 101 to 
 199; the second year 201 to 299; the third year 301 to 399; 
 and the fourth year 401 to 499. The first figure tells at once 
 in what school year the drawing is made and the last figures 
 give the consecutive number of the drawing. This is further 
 divided by having all second term drawings begin with 151, 
 251, etc. Thus the sixth drawing of the second term of the 
 first year made on a 12" x 18" sheet would be C-156. Drawings 
 to be used in the various shops of the school must be num- 
 bered consecutively beginning with 1101 preceded by the 
 proper letter designating the size; thus: D-1102. A record 
 of each drawing shall be kept. 
 
 10. Patterns will be listed A, B, etc., in the bill of mate- 
 rial. Hence pattern B on Drawing C-156 would be Patt. C-156 
 B. Plate 4. 
 
 CONVENTIONAL LINES 
 
 (See Plate 6) 
 
 11. Border lines shall be heavy full lines, from 1/32" 
 to 1/16" wide. 
 
 12. Visible edges and outlines of objects shall be repre- 
 sented by full lines of medium width. 
 
 13. Hidden edges and outlines of objects shall be repre- 
 sented by broken lines, consisting of short y 8 " dashes, some- 
 what lighter than medium lines, separated by 1/16" spaces. 
 
 14. Dimension lines shall be fine, solid lines, interrupted 
 for the figures expressing the dimension and terminated by 
 long, narrow arrow-heads; and drawn at least 14" from the 
 object. 
 
 15. Reference, or extension lines shall be fine, full lines, 
 drawn at right angles to the edge measured, from a point 1/32" 
 from the edge and projecting 1/16" beyond the arrow head. 
 
 16. Center lines shall be fine, broken lines, consisting of 
 long %" dashes, separated by single 1/16" dots and 1/16" 
 spaces. 
 
 17. Projection or Construction lines, including all lines 
 not essential outlines or edges of the object represented, shall 
 be fine 1/16" dotted lines. These are seldom inked, 
 
 Page Seventeen
 
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 PLATE 7 
 
 Page Eighteen
 
 18. A working drawing is one made for use in a work- 
 shop, in building construction, or erecting in the field. 
 
 19. The representation of an object on such a drawing 
 must follow the principles of orthographic projection. In all 
 standard drawings the third angle is used, Plate 7, 
 
 20. The front view must be placed below the top view, 
 or plan ; the end or side elevation at the corresponding side of 
 the front view or elevation; the bottom view below the front 
 elevation, Plate 7. If conditions demand, the end view may 
 be placed at the right or left of the top- view, or plan. 
 
 21. Two views are generally needed to represent an ob- 
 ject. Three views are often required while more may be 
 necessary. Sometimes one view with a section view is all 
 that is necessary, while in the case of a cylinder one view 
 showing the length with the diameter stated thus: 3" DIA., 
 will meet all requirements. Select the views that will give the 
 best idea of the piece, avoiding hidden edges. Plate 8, Figs. 1 
 and 2. 
 
 22. Working drawings are made %", 1", li/>", 2", 3", 4", 
 '6", 9" and 12" to the foot, that being 1/16, 1/12, i/ 8 , 1/6, 14, 
 1/3, %, % and full size respectively. Details are made full 
 scale or to as large a scale as possible. Scales are not given 
 on detail drawings. The 2" and 4" scales are to be avoided as 
 impractical, 
 
 23. Drawings are made either of the separate parts or of 
 the various parts properly assembled. The former are styled 
 detail drawings; the latter assembly drawings, 
 
 24. Drawings are made of objects as they would 
 naturally appear in use or in the assembled whole. 
 
 25. Show all details as near to full size as possible con- 
 sistent with size of sheet. 
 
 ASSEMBLY DRAWINGS 
 
 26. The assembly drawing is designed to show the inter- 
 relation of the parts, the space occupied by the machine, the 
 name and number of each part, the method of fastening, cen- 
 ter line distances which can be checked in erecting, etc. The 
 assembly drawing is usually made more elaborate than the 
 detail in that shading may be done at times, threads drawn 
 in their true form, or gear teeth shown, etc. 
 
 27. The assembly may be sectioned in part to show the 
 interior, the working of the component parts, etc. 
 
 28. In engine and machine drawings it is permissible to 
 omit in one view some construction which is sufficiently 
 
 Page Nineteen
 
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 Page Twenty
 
 shown in another view. This permits the showing of details 
 in the mechanism which would otherwise be obscured. 
 
 29. Preliminary assemblies are usually made full size 
 from sketches and are used by the designer in working out 
 the action of the mechanism. 
 
 30. Partial assemblies are made to show the details of 
 any system connected with the machine, as the lay-out of 
 wiring, piping, etc. 
 
 31. Piping and wiring drawings are often made in iso- 
 metric form that is similar to a photograph in which one pic- 
 ture may show top, front and all details. Such a drawing aids 
 the workman as it shows at a glance the location of all 
 couplings, valves, tees, elbows, etc. 
 
 DIMENSIONS 
 
 32. The drawings are dimensioned the actual size of the 
 piece regardless of the scale. 
 
 33. Dimensions and notes must be at least 14" from the 
 drawing.- Plate 8, Figs. and 4. 
 
 34. Dimensions are placed so as to read either from the 
 right-hand side of the drawing or from the bottom. Plate 8 
 and Plate 10. 
 
 35. All notes are placed either horizontally or vertically, 
 never at an angle. Plate 8, Fig. 4. 
 
 36. Everything must read from the lower and right- 
 hand side of the sheet. Plates 8, 9 and 10. 
 
 37. Dimension figures, including fractions, are placed 
 at the center of the dimension line, unless the space is very 
 limited, in which case the arrow-heads and figures are placed 
 on the outside of the space dimensioned. Plate 10. 
 
 38. The common fractions in y 2 's, 14 's, %'s, 1/16's, 
 1/32's, 1/64's only are used. Where very accurate work is 
 demanded, decimals are used. 
 
 39. The division-line of fractions must be in line with 
 the dimension line, and never inclined. Plate 10. 
 
 40. On drawings of machinery inches ale used up to 48". 
 48 inches and above are expressed in feet and inches, thus: 
 
 4 EL 10^. Plate 10. Where all dimensions are in inches the 
 inch marks may be omitted. Plate 2 
 
 41. Inches alone are used in drawings of furniture and 
 much cabinet work and interior finish. This is also the gen- 
 eral practice in the automobile industry. 
 
 42. Over all dimensions should be placed well outside 
 the drawing; shorter dimensions are placed inside these. 
 
 Page Twenty-one
 
 . 3 
 
 PLATE 9 
 
 Page Twenty-two
 
 Plates 8 and 9. A series of dimensions should be so arranged 
 as to facilitate checking. . 
 
 43. Dimensions must not be too far removed from the 
 part dimensioned. Measurements are placed so as to aid the 
 checker and the workman. Dimensions are often well placed 
 between the views. 
 
 44. Keep dimensions off the figure except where there 
 is a possibility of confusing the workman. Plate 8, Fig. 2. 
 
 45. Keep related dimensions, i. e., a length and width, on 
 thp same view if possible. 
 
 46. Dimensions given in one view must not be repeated 
 in another. 
 
 47. Avoid dimensioning from hidden edges. 
 
 48. Never use center lines for dimensions. 
 
 49. Base dimensions from center lines and finished sur- 
 faces. Make the drawing fool proof by tying up all holes or 
 cuts to center lines or finished surfaces. Plate 8, Fig. 4; Plate 
 9, Fig. 1. 
 
 50. Place center lines through the centers of all circles 
 and symmetrical drawings. Show center lines for every hole. 
 Plate 9. 
 
 51. Dimension to center lines of circles, not to circum- 
 ferences. Plate 9, Fig. 1. 
 
 52. Circles are dimensioned by their diameters; arcs by 
 their radii. All Radii should be marked R or Rad and all 
 diameters Dia or D, Ream, Turn, Bore, Core, etc. Plate 9, Fig. 
 1, and Plate 10. 
 
 53. Where there are several diameters in a given length 
 it is better to give them across the length rather than in an 
 end view. Plate 9, Figs. 2 and 3. 
 
 54. Never cross a dimension with a 'line. Break section 
 lines for a dimension or note if placed in a sectional area. 
 Plate 11, Fig. 1. 
 
 55. Since shop drawings are not to be scaled give all 
 necessary dimensions for laying out and finishing the work. 
 
 56. Drawings are figured for the machinist, cabinet 
 maker, or builder, as the case may be. Be careful to give 
 such dimensions as will be needed by the mechanic in laying 
 out the work. All figuring is up to you. Add all partial dimen- 
 sions and give "over all." Leave no adding or subtracting for 
 the workmen. This is your job. He has enough to figure out 
 without doing yours. 
 
 Page Twenty-three
 
 D/MELNS/ONS 
 
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 PLATE 1O 
 
 Page Twenty-four
 
 NOTES 
 
 57. Do not be afraid to use explanatory notes. Clear- 
 ness is all important. 
 
 58. All left-hand threads should be plainly marked. 
 
 59. Handed pieces should be marked Right (or Left) as 
 shown. 
 
 60. On tool details it is customary to add a note below 
 regarding Material, as Tool Steel, etc., etc. Harden and Grind, 
 etc. 
 
 61. On tool details the dimensions of the raw stock from 
 which part is to be made are sometimes given. 
 
 62. Use abbreviations where possible but be sure the 
 abbreviation is commonly used. The workman reads the 
 drawing not your mind. 
 
 SECTION VIEWS 
 
 63. A section view shows the surface as made by the 
 passing of a plane through a piece. The purpose of a section 
 is to show the shape of cores, thickness of stock, interior 
 mechanism, and assembly. Plate 11. 
 
 64. The point at which a section is made is indicated by 
 a short and long dash line, similar to a center line, and let- 
 tered: as A-A. Plate 11, Fig. 1. 
 
 65. The surface cut by the plane of section is indicated 
 by lines at 45 degrees spaced in proportion to the size of the 
 drawing, usually about 1/16" apart. Section all details as for 
 cast-iron. The various styles of cross-hatching need not be 
 used to indicate the material, often that for cast-iron and 
 babbitt only being used in actual practice. The material is 
 otherwise stated in connection with the name of the piece. 
 Cross hatch lines for cast-iron and for babbitt are fine. Plate 
 11. 
 
 66. Never section bolts, nuts, screws, shafts, spindles, 
 keys, arms of wheels (lengthwise), gear-teeth, etc. Plate 11, 
 Fig. 2, Plate 12, Fig. 1. 
 
 67. Never show hidden edges behind the line of section, 
 unless clearness positively demands it. 
 
 68. Make half section rather than full section views. 
 Plate 11. 
 
 69. Adjoining section areas have section lines running 
 in opposite directions. Plate 11. 
 
 Page Twenty-five
 
 SECT /OH O/V A- A 
 
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 Twenty-six
 
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 Page Twenty-seven
 
 6 CFtE W THREADS 
 
 /a U.S.STD. iz u.s. $TD. THD. PER IN L.H< 
 
 THP. PER IN. FIG. / 
 
 TAPPED HOLES 
 
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 Page Twenty-eight
 
 THREAD^ 
 
 70. U. S. Standard and V-threads should be indicated 
 by alternate light and heavy lines. The diameter and pitch 
 should always be given. Plate 13. Either method as shown 
 in Fig. 1 may be used. 
 
 71. Any other than the standard thread should be stated 
 in a note. If a screw has a left-hand or multiple thread, a note 
 should call attention to the fact. Plate 13, Fig. 3. 
 
 72. A tapped hole should be shown by a circle indicating 
 the size of the drill and a larger concentric circle in hidden 
 edge line, indicating the size of the tap. A note should state 
 the diameter and number of the tap, thus: l"-8 TAP. U. S. Std. 
 Plate 13. 
 
 73. Never make detail drawings of standard screws, 
 bolts and nuts. 
 
 FINISH 
 
 74. The finish mark, "//' made crossing the line indicat- 
 ing the surface finished, shows that the surface is to be fin- 
 ished as left smooth by the tools. Plate 8, Fig. 4; Plate 9, 
 Fig. 1. A small fraction placed a little above and to the right 
 of the finish mark indicates the amount required for finishing. 
 Plate 11, Fig. 1. 
 
 75. Other special finishes as turn, bore, drill, knurl, 
 ream, spot-face, as well as core, are so stated on the drawing. 
 Plate 9 and Plate 13. 
 
 76. If a piece is to be finished all over, the note, "Finish 
 all over" (F. A. O.), may be placed near the drawing of the 
 piece or in connection with its name in the bill of material. 
 Plate 9, Fig. 2. 
 
 77. On all machine parts use following note: "Remove 
 all burs," "Break all sharp machined edges." 
 
 Page Twenty-nine
 
 PLATE 14 
 
 Page Thirty
 
 MACHINE. SCREW HEADS. 
 
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 Page Thirty-one
 
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 PLATE 16 
 
 Page Thirty-two
 
 LIMITS 
 
 78. In cases where great accuracy is needed the work- 
 man is required to turn out the piece correct within limits. 
 These vary a hundredth to a ten-thousandth for instance, 
 according to the accuracy required. 
 
 79. Limits are expressed decimally. The amount over 
 size is placed above the dimension line after the dimension 
 figure while the amount under size is placed below the dimen- 
 sion line. 
 
 PATTERN AND FORGING DRAWINGS 
 
 80. There is a growing tendency on the part of manu- 
 facturers to send full size pattern drawings showing core 
 prints, draft, allowance for finish, parting lines, etc., into the 
 die sinking or pattern rooms. These drawings are usually 
 inked in on the original pencil work to avoid the distortion 
 produced by the tracing cloth and blue printing. Pattern and 
 die drawings are usually made by experienced pattern or die 
 makers who have been trained in drafting. Such drawings 
 are intended to supplement the ordinary drafts made by each 
 pattern maker or the foreman. 
 
 81. Pattern drawings should contain certain notes to 
 assist the pattern maker such as "Break all sharp edges ex- 
 cept as noted," etc. 
 
 82. Forging drawings should be very explicit in regard 
 to the shape of the part. All centers should be located and 
 drafts shown. Dimensions not related to or required by the 
 pattern or die maker's work need not be shown. 
 
 CHECKING DRAWINGS 
 
 1. See that projections and sections are correct. 
 
 2. On assembly drawings check for interference and 
 clearances. 
 
 3. See that general conventions and standards have 
 been observed. 
 
 4. Check all dimensions in regard to arrangement and 
 accuracy. 
 
 5. See that all finished surfaces are marked. 
 
 6. See that the bill of material is complete and correct. 
 
 7. See that the title and drawing number are correct. 
 
 8. Check all notes for arrangement. 
 
 9. See that proper weights of lines and size of letters 
 and figures have been used and that the drawing is correct in 
 every detail. 
 
 Page Thirty-three
 
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 s 
 
 k 
 
 
 
 
 
 
 5 
 
 ^ S 
 
 3i ^ 
 
 
 *v 
 
 
 X 
 
 X , 
 
 ^ ^ 
 s N 
 
 
 -- 
 
 , .fo/ 
 
 
 
 
 t 
 
 /. 
 
 
 CENTERS 
 
 (*>|jo^ 
 
 GR/MD/MG 
 
 "B "CF/V TER 
 
 B C/VTER 
 6 HOLES 
 
 F.A. O. 
 
 PLATE 17 
 
 Thirty -four
 
 V J X |M ')]<b 
 
 nn 
 
 * * 
 
 O 5! 
 
 a 5 
 
 M f 
 
 ,^1 
 
 5 1 
 
 f/- 
 -r^<? 
 
 , 1-- ,-r n^ 
 
 V/- 
 
 
 *) 
 
 L_ 
 
 PLATE 18 
 
 Page Thirty-five
 
 DECIMAL EQUIVALENTS OF FRACTIONAL 
 PARTS OF ONE INCH 
 
 & 
 
 _3_' 
 64 
 
 ,015625 
 03/25 
 046875 
 0625 
 
 64 
 
 32 
 
 64 
 
 _9_ 
 64 
 
 09375 
 109375 
 
 , 
 8 
 
 64 
 13__ 
 64 7 
 
 15625 
 17)875 
 
 3_ 
 
 Iff 
 
 203125 
 
 64 
 17 
 
 234375 
 25 
 
 64 
 2/ 
 
 . 
 
 /6 
 
 64^ 
 23 32_ 
 64 
 
 25 
 
 64^3 
 27 1 
 64 
 
 23 j 
 
 64,5 
 
 B 
 
 .359375 
 
 .375 
 
 .390625 
 
 .4375 
 
 64 
 
 ..484375 
 
 JL.5 
 2 
 
 33 
 
 64 
 37 
 
 6*4 
 
 4J. 
 
 64 2/ 
 43^2- 
 
 5 
 3" 
 
 .515625 
 
 .53125 
 
 .546875 
 
 .5625 
 
 .578125 
 
 .59375 
 
 .609375 
 
 .625 
 
 .640625 
 
 64 
 
 45 (S 
 
 .703125 
 
 32 
 
 64 
 45 
 
 .734375 
 .765625 
 
 5' 
 6? 
 
 M_ 
 64^7 
 
 5532 
 
 .796875 
 
 13 
 
 .84375 
 
 64 
 57 
 
 64 
 
 6L 
 
 64^ 
 
 6332 
 64 
 
 /5 
 
 ,875 
 .890625 
 .9O625 
 .921875 
 .9375 
 
 /6 
 
 .96875 
 .984375 
 
 PLATE 19 
 
 Thirty-six
 
 U.S. STANDARD 
 THREADS BOLTS AND NUTS 
 
 ETER 
 
 O.OFTH'DS 
 PER INCH 
 
 OT 
 EAD 
 
 DIAMETER 
 AT RO 
 OF THR 
 
 DIAMETER 
 OF TAP DRILL 
 
 DIMENSIONS OF NUTS 
 AND BOLT MEADS 
 
 ACROSS 
 FLATS 
 
 IB 
 
 
 <o 
 
 o o u_ 
 
 < O 
 
 THICKNESS 
 F NUT 
 
 !-< 
 r S 
 
 on 
 
 LJ u. 
 310 
 
 20 
 
 0.185 
 
 '/e 
 
 0.578 
 
 0.707 
 
 
 Vie 
 
 8 
 
 0.240 
 
 1/4 
 
 0.686 
 
 0.840 
 
 3 /8 
 
 16 
 
 0.294 
 
 Vie 
 
 '!/., 
 
 0.794 
 
 O.972 
 
 Vs 
 
 14 
 
 0.345 
 
 25 
 
 5 /32 
 
 0.902 
 
 05 
 
 13 
 
 O400 
 
 V8 
 
 I.OII 
 
 1.237 
 
 ~w 
 
 vz 
 
 12. 
 
 0.454 
 
 1.119 
 
 1.370 
 
 It 
 
 0.507 
 
 iw 
 
 I.Z27 
 1.444 
 
 I.5O2 
 
 Vs 
 
 3/4 
 
 10 
 
 0.6ZO 
 
 1.768 
 
 7 6 
 
 0.731 
 
 .660 
 
 2.033 
 
 8 
 
 O.838 
 
 1.877 
 
 71.29S 
 
 O.939 
 
 2.093 
 
 2563 
 
 1.064 
 
 Z.310 
 
 2.S28 
 
 1.158 
 
 2.527 
 
 3.O93 
 
 IA 
 
 1.283 
 
 2.743 
 
 3.358 
 
 I'/Z 
 
 51/21 
 
 1.389 
 
 Z.960 
 
 3.623 
 
 1.490 
 
 3.176 
 
 3.88e 
 
 1.615 
 
 3.393 
 
 4.1S4 
 
 ) 7 /8 
 
 4 'A 
 
 1.711 
 
 3.G09 
 
 4.419 
 
 1.961 
 
 3 'A 
 
 4.043 
 
 2.175 
 
 3% 
 
 A476 
 
 5.479 
 
 2'/z 
 
 2.4Z5 
 
 414 
 
 A909 
 
 6.OIO 
 
 Z.629 
 
 ^.342 
 
 6.540 
 
 2.879 
 
 5.715 
 
 7070 
 
 3'/4 
 
 314 
 
 3.IOO 
 
 5% 
 
 6.Z08 
 
 7600 
 
 3.317 
 
 6.641 
 
 8.131 
 
 27s 
 
 3.567 
 
 7074 
 
 8.661 
 
 4J4 
 
 2% 
 
 3.798 
 
 7.SO& 
 
 4 ' 
 
 4.028 
 
 7.941 
 
 4% 
 
 4.255 
 
 5.374 
 
 4V4 
 
 3% 
 
 2'/z 
 
 4.480 
 
 8-807 
 
 IO.782- 
 
 5J/4 
 
 4.730 
 
 9.240 
 
 IK3I2 
 
 4.953 
 
 8% 
 
 9.G73 
 
 M.84Z 
 
 i'/z. 
 
 4% 
 
 5-*/4 
 
 5.203 
 
 IO.IO6 
 
 IZL.373 
 
 5.423 
 
 \ 0.539 
 
 12.^03 
 
 PLATE 20 
 
 Thirty-seven
 
 TRACING 
 
 It is often desirable to make a more permanent and service- 
 able record of a drawing than would be possible if only the inked 
 original drawing were used. To accomplish this a tracing of the 
 penciled drawing is made on tracing cloth. From this tracing as 
 many blue-prints as desirable may be made these are durable, 
 since they will withstand the wear and the danger of erasure from 
 the weather and hard usage. 
 
 The tracing cloth should be cut somewhat larger than the 
 drawing, so that the thumb-tack holes may be removed when the 
 tracing is trimmed to the proper size. This can readily be done, 
 since 36" cloth actually measures 37" wide, being 36" wide between 
 the red lines near the edge. 
 
 Tack the cloth down to the board so that it will be tight and 
 i'ree from wrinkles, as the tracing may be done more rapidly. The 
 cloth should have no creases or breaks in it from ill usage. Either 
 the dull or the glossy side of the cloth may be used. A great many 
 prefer and use the dull side because in the drafting room correc- 
 tions in pencil may more readily be made on this side than on 
 the glossy side. 
 
 Dust the surface over with chalk, magnesia or talcum powder. 
 Rub this lightly into the surface and brush all the loose particles 
 off thoroughly to rid the surface of grease and grit and to insure 
 a ready flow of the ink. 
 
 In order to maintain a uniform width of line throughout keep 
 the same amount of ink in the pen, about a quarter of an inch at 
 the most. Keep the pen clean. It will be necessary to clean the 
 pen often, as little particles of chalk will be picked up which inter- 
 fere with the even flow of the ink. If it is impossible to complete 
 the whole tracing at one sitting finish one part, including circles, 
 straight lines, medium and fine. This is most desirable, as the 
 cloth is liable to stretch during the intervening time between sit- 
 tings, making it difficult to readjust the tracing to the drawing. 
 
 Erasing Use an ordinary eraser in erasing. Never use one 
 with sand in it. Never use a steel eraser. These either destroy the 
 surface of the cloth, making it impossible to retrace, or a hole is 
 cut in the cloth, ruining the whole tracing. After erasing it is often 
 necessary to build up from a fine line to one of full weight. 
 
 Page Thirty -eight
 
 University of California 
 
 SOUTHERN REGIONAL LIBRARY FACILITY 
 
 Return this material to the library 
 
 from which it was borrowed. 
 
 SEP 241940 
 SEP 2 4 1990