Introductory Concepts and BIS Conventionspress

Press Basudeb Bhattacharyya Associate Professor Department of Aerospace Engineering and Applied Mechanics Indian Institute of Engineering Science and Technology, Shibpur University

Oxford

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First published in 2018

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ISBN-13: 978-0-19-948749-3 ISBN-10: 0-19-948749-9

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A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. William Strunk, Jr Drawing is an art and artists aim at drawing objects the way machine parts after the design is finalized. This is also why they are visible to the naked eye or to beautify objects be- gradually the study of such software has become a part of yond their original form. Engineering or machine drawing the curriculum of machine drawing. Keeping this in mind is somewhat different in the sense that it requires the engi- this book, Machine Drawing, aims at providing readers a neer to not only sketch the object almost as a photographic comprehensive understanding of the subject. image but also represent it in different views. These different views are detailed exploded views of the object that ABOUT THE BOOKPress are required to manufacture or engineer a product. Machine This book is primarily meant for undergraduate students of drawing in particular requires not just a steady hand but mechanical engineering for the course on machine draw- also a sense of perspective. ing. It takes readers through a gradual process of master- Machine drawing is a subject of utmost importance in ing the subject by first providing a detailed discourse on the mechanical engineering curriculum because the manu- elementary generalized items covering drawing boards, facturing of a machine depends completely on the design sheets, instruments to conventional representation of vari- and drawing, including dimensional specifications, of the ous items in context with the recommendations of relevant machine down to the last minute detail. For fabricating or latest BIS codes of practice. A list of relevant codes is also manufacturing a machine or a component of a machine,University the provided in the Appendix as a ready reckoner. In modern design is first prepared through analytical computations. times, drawings prepared by hand using pencils or inking Then the designed component is converted into pictorial device are losing their importance especially in case of re- representation on paper. It may be represented through petitive and large scale use in industries as they cause num- two-dimensional or three-dimensional drawings, or both, ber of inconveniences. Computer-Aided Drafting (CAD) is depending on the requirement. For two dimensional rep- the best suited alternative in such cases. Hence, relevant resentations, orthographic views are used and for picto- Oxford chapters are supplemented with drawing methods using rial representations, conventionally isometric drawings are AutoCAD. used. For the manufacturing process, the knowledge of presentation of limits, tolerances, etc., on paper is a prerequi- KEY FEATURES site. All these, including the method of dimensioning, must follow the methods laid out in the various codes of practice Comprehensive Coverage The book provides compre- published by the Bureau of Indian Standards (BIS). In fact, hensive coverage of drawing instruments, sheets, lettering, starting from the size and shape of drawing boards, draw- and dimensioning, which enable students to understand ing tools, to the representation methods of machine compo- different aspects of machine drawing. This is followed by nents, are all guided by Indian Standard codes of practice. a chapter on sectional views focusing on both obvious and Traditionally this subject depended completely on manual specified section planes. A wide variety of fastening- ar drawings that were made using drafters. However, with the rangements such as welding, riveting, cotter, and pin along passage of time, computers have taken over, and machine with the different styles of attachment for shaft and pipe are parts are drawn using software applications for 2D and 3D discussed at length. Assembly and disassembly drawings design and drafting such as AutoCAD and SOLID EDGE. are discussed in terms of different components of inter- Design engineers now use these software for modelling nal combustion engine and steam power plant. Moreover,

© Oxford University Press. All rights reserved. vi Preface some machine tools and their components and some mis- Chapter 3 presents different fastening arrangements that cellaneous machines are discussed. include welded, riveted, and threaded joints along with Illustrations Figures are the soul of this book. The size of variety of threads, bolt–nut assembly, and their drawing the book has been especially chosen to ensure that there methods. is enough space to illustrate figures with clarity so that Chapter 4 discusses shaft and pipe joining arrangements students get an explicit view of the drawings. Neat labels, and shaft attachments. Different types of valves and belt– proper dimensioning, and different views make the figures pulley assembly are detailed here. This chapter also in- totally unambiguous and easy to analyse and understand. cludes of a variety of bearing, gears, and worm wheel. Full pages are dedicated to a number of complicated and Chapter 5 discusses part and assembly drawings in rela- intricate figures. As much as possible, it has been tried to tion to parts of internal combustion engine (ICE) and steam place figures as close to the relevant text so that the stu- power plant. Major components of ICE and steam power dents do not have to flip pages while reading. plant are suitably presented here either in orthographic or isometric or both systems. AutoCAD and BIS codes Each relevant chapter has an Chapter 6 provides detailed drawings of some common AutoCAD supplement which provides drawing examples machine tools and some miscellaneous equipment such as using AutoCAD. The book presents specifications of BIS crane hook, surface roughness measuring stand, screw jack, codes of practice, up to the latest available edition, wher- knife switch, centrifugal pump, relief valve, belt drive, ever required. worm reduction gear box, and bevel gear junction box. Rich Pedagogy There are a number of solved examples in each chapter with step-by-step solutions. A detailed point- ACKNOWLEDGEMENTSPress wise recapitulation at the end of each chapter revisits all the It is a great pleasure and honour for me to be associated important points discussed in the chapter making for a fine with Oxford University Press. I express my sincere grati- guide for revision before the exams. This is followed by tude and thanks to the entire editorial team and production numerous multiple-choice questions, review questions, and department of Oxford University Press for publishing my numerical problems that promise to provide students ample book in time while maintaining a high degree of precision practice to make them perfect in the subject. Answers to the and accuracy. I thank the senior teachers of my department multiple choice questions have also been provided at the for their encouragement. I also express gratitude towards end of the chapters. my family members for their unfathomable inspirations. A Universityvery special mention goes to Mr Subir Pal of M/s Books CONTENTS AND COVERAGE and Equipment Distributors, Howrah. I am thankful to Prof. D.V. Srikanth (St. Martin’s Engineering The book is divided into 6 chapters. A brief of each of the College, Secunderabad) for his valuable feedback and con- chapters is mentioned below: tribution in enhancing the content. Chapter 1 deals with different items in context with the Every effort has been made to produce an error-free text; provisions laid out in the various codes of practice pub- however, I would be grateful if readers can point out any lished by the Bureau of Indian OxfordStandards. unintended error or discrepancy. Readers can write to me Chapter 2 discusses how to draw different sectioned with their suggestions and feedback on basubec@gmail. views of objects. The standard conventions of hatching com. pattern for different section planes are discussed following BIS conventions. Basudeb Bhattacharyya

1. Introductory Concepts and Representation of Assembled Parts 21 BIS Conventions 1 Designation and Dimensioning of Threaded Introduction 1 Parts 21 Classification of Drawing 1 Conventional Representation of Springs 22 Code of Practice 1 Helical Compression Springs 22 Drawing Instruments 2 Helical Extension Springs 23 Drawing Board 2 Torsion Springs 23 T-Square 2 Disc SpringsPress 23 Set-Square 3 Spiral Springs 23 Protractor 3 Leaf Springs 23 Drafting Machine 3 Conventional Representation of Gears 24 Ruling Machine 4 Contours 24 French Curves 4 Pitch 24 Scale 5 Root Surface 24 Pencil and Eraser 5 Teeth 24 Compass and Dividers 6 2. Sectional Views 27 Size and Layout of Drawing Sheets University6 Introduction 27 Dimension 6 Convention for Placement of Section Planes 27 Title Block 7 Types of Section Planes 28 Borders and Frame 7 Obvious Section Plane 28 Centring Marks 7 Specified Section Plane 28 Grid Reference System 8 Convention for Placement of Sectioned Views 30 Trimming Marks 8 Section of Interpenetrated Solids 31 Folding of Drawing SheetsOxford 9 AutoCAD Supplement 43 Description of Different Types of Lines 10 Lines Used in Construction Drawing 11 3. Different Fastening Arrangements 49 Lines Used in Mechanical Drawing 11 Introduction 49 Patterns of Lettering 13 Welded Joint 49 Patterns of Section and Other Conventions 15 Types of Welding Processes 49 General System of Dimensioning 16 Types of Welds 50 Functional Dimension 16 Symbols of Welds 54 Nonfunctional Dimension 16 Edge Preparation for Welding 56 Basic Rules of Placement of Dimensions 16 Riveted Joint 56 Elements of Dimensioning 16 Types of Rivets 57 System of Dimensioning 17 Types of Riveted Joints 58 Arrangement of Dimensions 18 Parameters Associated with Riveted Joints 59 Special Indications in Dimensioning 19 Application in Structures with Conventional Conventional Representation of Threads and Sections 65 Threaded Parts 20 Application in Shells 67 Representation of Single Entity 20 Caulking and Fullering 69

© Oxford University Press. All rights reserved. viii Contents Threaded Fasteners 70 Wall Bracket Bearing 147 Types of Threaded Fasteners 70 Self Aligning Bearing 147 Types of Threads 71 Hanger Bearing 149 Parameters Associated with Threaded Gears 149 Fasteners 72 Gear Terminology 150 ISO Thread Profile 73 Proportion of Dimensions for Different Other Thread Profiles 79 Parameters 152 Types of Screws 81 Profile of Gear Tooth 152 Representation of Screws 82 Drawing Profile of Gear Tooth 152 Bolt and Nut Assembly 82 Spur Gear 154 Hexagonal-headed Bolt and Hexagonal Nut 83 Helical Gear 155 Square-headed Bolt and Square Nut 85 Bevel Gear 156 Locking Arrangement of Nuts 86 Worm and Worm Wheel 157 Representation of Nuts 89 Rack and Pinion 159 Washers 89 AutoCAD Supplement 159 Variety of Foundation Bolts 89 5. Part and Assembly Drawing 165 AutoCAD Supplement 90 Creating a Block 90 Introduction 165 Inserting a Block 92 General Arrangement Drawing (GAD) 165 Editing a Block 93 Assembly Drawing 165 Part DrawingPress 166 4. Shaft and Pipe Joiners and Shaft Internal Combustion Engine (ICE) 166 Attachments 97 Cylinder 167 Introduction 97 Piston 170 Keyed Joints 97 Piston Ring 172 Types of Keyed Joints 98 Piston Pin 175 Cotter Joints 102 Connecting Rod 176 Knuckle Joint 104 Crankshaft 178 Shaft Coupling 105 Cams and Followers 180 Rigid Shaft Coupling University105 Valve Train 187 Flexible shaft coupling 108 Venturi Carburettor 190 Pipe Joints 112 Fuel Pump 191 Parameters Related to Pipe Threads 113 Fuel Injector 191 Forms of Pipe Threads 114 Spark Plug 193 Dimensions of Pipe Threads 115 Oil Pump 194 Types of Pipe Joints 115 Water Circulating Pump 195 Special Pipe Joints Oxford 118 Steam Power Plant 197 Pipe Fittings 119 Feed Pump 197 Valves 121 Steam Injector 198 Symbols used in Pipe Network 126 Feed Check Valve 198 Belt and Pulley 128 Steam Stop Valve 199 Belts and its Varieties 128 Safety Valve 201 Pulleys 129 Blow-off Cock 206 Bearing 133 General Arrangement of a Steam Engine 206 Fluid Bearing 134 Cylinder 207 Rolling Element Bearing 136 Piston and Piston Rod 207 Plummer Block Bearing 139 Piston Rings 208 Inclined Plummer Block Bearing 141 Stuffing Box 209 Marine Engine Shaft Bearing 142 Crosshead 210 Pedestal Bearing 143 Connecting Rod 212 Footstep Bearing 143 Crank 214 Swivel Bearing 145 Eccentric 215

© Oxford University Press. All rights reserved. Contents ix D-slide Valve 217 Jigs and Fixtures 240 Speed Governor 217 Drilling Jig 240 6. Machine Tools and Milling Jig 244 Miscellaneous Drawings 223 Tumble Jig 248 Jig for Valve Stem Hole 249 Introduction 223 Indexing Fixture 249 Lathe 223 Miscellaneous Devices 251 Three-jaw Chuck 224 Crane Hook 251 Four-jaw Chuck 224 Surface Roughness Measuring Stand 251 Tool Post 226 Quick Change Drill Holder 252 Tool Holder 228 Screw Jack 254 Tail Stock 231 Knife Switch 255 Slide Rest 231 Centrifugal Pump 255 Revolving Centre 233 Relief Valve 255 Shaper 234 Three Way Stop Valve 255 Tool Head 234 Multiple Disc Friction Clutch 257 Clapper Box 236 Belt Drive 257 Hand Drill 236 Worm Reduction Gear Box 261 Vice 238 Bevel Gear Junction Box 264 Bench Vice 238 Pipe Vice 238 Reference CodesPress of Practice 267 Machine Vice 238 Bibliography 269 Swivel Vice 240

University

Oxford

Key Concepts

· Classification of drawing and the standard code of practice · Various drawing instruments and the corresponding code provision · Sizes and layout of drawing sheets and folding pattern as per the BIS code of practice · DifferentUniversity types of lines and lettering as per the BIS code of practice · Patterns of sections and general system of dimensioning as per the BIS code of practice · Conventional representations of threads, threaded parts, springs, and gears as per the BIS code of practice Oxford 1.1 INTRODUCTION (i) geometrical drawing, (ii) machine drawing or mechanical Drawing is a form of visual expression. It is generally concerned with the mark- drawing, ing of lines and areas onto paper. The origin of drawing dates back to prehistoric (iii) civil drawing, times when rock and cave drawings and marks on sand and earth were used as (iv) architectural drawing, and the mode of communication. By the twelfth to thirteenth centuries ad, monks (v) electrical and electronics engi- started preparing illuminated manuscripts on vellum or parchment and were us- neering drawing. ing lead styli to draw lines for their writings or for the outlines of illuminations. Although our purview will be limited Fourteenth century onwards, we find evidences of drawings on paper. to machine drawing, this introductory chapter is a generalized one and is com- 1.2 CLASSIFICATION OF DRAWING mon to all sorts of technical drawing.

Drawing may be broadly classified as artwork and engineering drawing. The 1.3 CODE OF PRACTICE term technical drawing is synonymous with engineering drawing. From engi- Drawing is the language of engineer- neering point of view, engineering drawing can be further classified into: ing and therefore it should follow a

© Oxford University Press. All rights reserved. 2 Machine Drawing grammar (rules). In order to standard- drawing board should be 20–25 mm, (generally 22 mm). The standard dimen- ize the rules for drawing, in 1955, the sions of the drawing boards as per the BIS code are given in Table. 1.1. Indian Standards Institution (ISI) published IS:696—1955, code of practice Width for general engineering drawing. Af- Thickness ter the publication of its second revision in 1972, the contents of the code Strips were harmonized with the relevant rules and regulations followed by the International Standards Organisa- tions (ISO), and so after withdrawing IS:696—1972, a series of standards were published. On July 1, 1987, the Battens ISI was renamed as the Bureau of In- Length dian Standards (BIS). To serve as a Working edge ready reckoner, SP:46—1988 (a special publication containing the rules and standards of general engineering Fig. 1.1 Drawing board drawing) was published by the BIS. Its latest revised edition is SP:46— Table 1.1 Specifications of drawing board Press 2003. Throughout this book we have followed this code and other relevant Designation Length ¥ Width (mm) Thickness (mm) Usable Sheet Designation codes of the latest edition of BIS. D00 1525 ¥ 1220 22 — D0 1270 ¥ 920 22 A0 1.4 DRAWING INSTRUMENTS D1 920 ¥ 650 22 A1 When we start drawing, primarily we D2 650 ¥ 470 22 A2 require a board on which the paper is D3 500 ¥ 350 22 A3 attached and some other instruments University for drawing lines and curves. Let us now T-Square discuss the various drawing accesso- The T-square is a frequently used drawing equipment. It is primarily used for ries (e.g., drawing board, T-square, set- drawing horizontal lines and for guiding the set-square to draw vertical lines or square, protractor, drafting machine, inclined lines. It is made of a thin long strip, called blade, that is fitted perpen- ruling machine, French curves, scale, dicularly to a horizontal strip, called stock, in such a manner that the assembly pencil, eraser, compass, and dividers) resembles alphabet ‘T’ (Fig. 1.2). The side of the blade with which horizontal conforming to the BIS specification.Oxfordlines are drawn is called the working edge. Previously, mahogany wood was used to make T-squares, but nowadays celluloid is used. Table 1.2 lists the sizes Drawing Board of T-square that are available. In India, the boards used for drawing are made as per the specification laid down in IS:1444—1989 (the latest BIS code of practice). The working surface of the drawing board should be Working edge made either of benteak, blue pine, fir, cypress, oak, or red cedar wood. Bat- Blade 90° tens at the back of the board, as shown in Fig. 1.1, should be made either of aini, anjan, bijasal, black chuglam, Stock padauk, safed siris, salai, sissoo, teak, or walnut wood. The thickness of the Fig. 1.2 T-square

Drawing board Drawing board Drawing sheet Pencil moves left Drawing sheet to right

T-square 15°

75° 105° T-square

(a) (b)

Fig. 1.3(a) Drawing parallel lines with T-square Fig. 1.3(b) Drawing inclined lines with T-square and set-squares

Table 1.2 Sizes of T-square The procedures for drawing horizontal lines and lines at different angles with Length of Working the help of a T-square and set-squares are illustrated in Figs 1.3 (a) and (b). Designation Edge (mm) Set-Square T0 1500 Set-squares are transparent right-angled triangular strips that are made of cel-PressT1 1000 luloid. Set-squares are of two types: (i) right-angled isosceles triangular shaped T2 700 with included angles 45°–90°–45°, conventionally called 45° set-square and T3 500 (ii) right-angled triangular shaped with included angles 30°–90°–60°, conventionally called 30°–60° set-square. The triangles may be solid or hollow (see the 45° set-squares are available in Figs 1.4 (a) and (b)). The various sizes of a set-square are designated as per the 150- to 200-mm size and the 30°–60° length of the longer side of the triangle containing the right angle. Generally, set-squares are available in 200- to 240-mm size. A set-square alone or in combination with a T-square can University be used to draw inclined and parallel lines (see Figs 1.5 and 1.3 (b)). All the 150–200 200–240 external edges of a set-square are bev- elled so that when a pen is used the ink does not spread. Some set-squares (a) (b) also have the centimetre scale in- Fig. 1.4 Solid and centrally hollow set-squares scribed and this helps in drawing lines Oxford of desired length.

90° 75° Protractor 105° 120° 60° The protractor (Fig. 1.6) is a semicir- 45° cular strip that is made of transparent 135° celluloid. It is inscribed with an an- 30° gular scale of at least 1° subdivision 150° along the semicircular periphery and is used to draw any angle. 165° 15° Drafting Machine The drafting machine is a modern compact instrument (Fig. 1.7) that Horizontal line can replace the use of T-square, set- Fig. 1.5 Use of set-square to draw lines at different angles squares, normal measuring scale, and

© Oxford University Press. All rights reserved. 4 Machine Drawing protractor. It is attached to the drawing board with a clamping knob. It has 80 100 110 70 90 120 two scales, generally graduated, fixed 60 100 80 110 70 130 50 60 at right angles to each other but can 120 50 140 40 130 40 move in any direction. A scale-fixing 150 140 knob controls this movement. An an- 30 30 160 150 Scale fixing knob gular scale is attached under the scale- 20 Parallel bars 20 fixing knob, which is used to draw 160 170 10 Angular scale 10 170

lines at any angles. 180 Drawing 270 0

board 0 180 Ruling Machine The ruling machine is a typical draw- Fig. 1.6 Protractor ing instrument used to draw horizon- Clamping tal parallel lines, vertical parallel lines, knob Scale fixing knob and inclined lines. Commercially, it is Parallel bars Scales known as roll-n-draw machine. Figure Angular scale 1.8 illustrates a ruling machine. Drawing board French Curves Press French curves are templates of lines of different curvatures of different radii Clamping and are made of either wood, metal, knob or plastic. These are used to draw a Scales smooth line through predetermined points or to draw curves of varying radii. Figure 1.9 shows different types of French curves that are available. Let us Fig. 1.7 Drafting machine now see how to draw a smooth curve University using a French curve. Draw a line (see Fig. 1.10) from point 1 to point 3 only with one side of the curve. Then draw a line matching points 3 to 4 with the other suitable part of the curve. At the next stage, match points 4 to 6 and proceed accordingly. Oxford

(a)

(b)

Fig. 1.8 Use of ruling machine Fig. 1.9 Different types of French curves

© Oxford University Press. All rights reserved. Introductory Concepts and BIS Conventions 5 6 Pencil and Eraser 5 5 4 6 4 The modern wood-cased graphite stick 3 3 pencils were made for the first time in 5 7 4 8 1662 in Nuremberg, Germany. The 3 9 2 most common type of pencil casing 10 is a thin wooden jacket permanently 1 11 bonded around the core. Wooden pen- (a) (b) (c) cils are commonly referred to as lead pencils, though these never contained 7 lead. The cores are mostly made of 6 8 graphite mixed with a clay binder. 9 7 These pencils are graded according 9 to the European system using alpha- 10 bets from H (for hardness) to B (for 11 blackness) as well as F (for fine point). The standard writing pencil is graded (d) (e) (f) as HB. It is believed that this grading system might have been developed in Fig. 1.10 Use of French curve Pressthe early 1900s by Brookman, an Eng- lish pencil maker. Table 1.4 shows the Scale different grades of pencils, ranging In the present context, the word scale does not refer to any length-measuring from a very hard light-marking pencil device. IS:10713—1983 (the latest BIS code conforming to ISO:5455—1979) to a very soft black-marking pencil. defines a scale as the ratio of linear dimension of an object represented in origi- Mechanical pencils are those in nal drawing to real linear dimension of the object itself. A scale where the ratio which the graphite stick is not bonded is 1:1 is called a full-size scale and where the ratio is larger than 1:1 is called an to the outer casing. They are designed enlargement scale and is represented as X:1. A scale where the ratio is smaller such that the graphite stick core is than 1:1 is called a reduction scale and is representedUniversity as 1:X. The choice of the extended mechanically as its point is scale entirely depends on the complexity of the object and the purpose of its rep- worn away. Mechanical pencils are resentation. The designation of the scale used on the drawing must be inscribed broadly of two types: propelling type in the title block of the drawing. The recommended scales for technical drawing and clutch type. The advantage of these are given in Table 1.3. pencils is that they provide lines of constant thickness without requiring sharpening, making them well suited Table 1.3 Recommended scales of drawing Oxford to technical drawing. The graphite Type of Scale Ratio of Scale sticks used in mechanical pencils are Full size 1:1 available in diameters of 0.13, 0.18, Enlargement scale 50:1 20:1 10:1 0.25, 0.35, 0.5, 0.7, 1, 1.4, and 2 mm, 5:1 2:1 conforming to the international code Reduction scale 1:2 1:5 1:10 of practice ISO:9175 (Part I)—1988. Eraser is a small piece of rubber 1:20 1:50 1:100 (or a similar substance) that is used 1:200 1:500 1:1000 for removing marks of pencils and 1:2000 1:5000 1:10000 pens. Erasers have a rubbery consis- tency and may be of different colours, Table 1.4 Grades of wooden pencils though mainly white. Edward Nairne (1726–1806), an English optician Grades and instrument maker, developed the ¨ Hardest ¨←Harder Medium Softer Æ Softest Æ first widely marketed rubber eraser 9H 8H 7H 6H 5H 4H 3H 2H H F HB B 2B 3B 4B 5B 6B 7B 8B 9B in 1770. Nowadays, wooden-cased

© Oxford University Press. All rights reserved. 6 Machine Drawing pencils are also available with erasers 1.5 SIZE AND LAYOUT OF attached to their ends. In the United DRAWING SHEETS Kingdom, an eraser is very commonly called as rubber. The size and layout of preprinted drawing sheets for any fields of tech- y Compass and Dividers nical drawing will be discussed with = 2 x reference to IS:10711—2001, con- y x A pair of compasses, commonly known forming to ISO:5457—1999 and as compass, is used for drawing cir- SP:46—2003. cles and arcs in technical drawing. It is also known as a drafting compass. A Dimension x compass is usually made up of metal The drawing sheets used for draft- and consists of two legs connected by ing technical drawing are available in Fig. 1.13 Proportion of drawing sheet an adjustable hinge. Its one leg has a sizes of A0, A1, A2, A3, and A4. The sharp spike at its end and the other leg basic principle to determine the size (trimmed) of a drawing sheet for any tech- is equipped with a holder for wooden nical product documentation is as follows: pencils, leads, or inking pens (see Figs (i) Consider one right-angled isosceles triangle of equal side x (see Fig. 1.13). 1.11 (a) and (b)). The dividing com- 22 Therefore, the length of the hypotenuse will be yx=+xx= 2 . Ro- pass (or simply divider) is used to tate this hypotenuse anticlockwise by an angle of 45° so that it becomes measure distances. It looks similar to vertical. Hence the size of the sheetPress is length y and width x. Therefore, the drafting compass, but both its legs the ratio of the two sides xy::= 12. are identical and have spikes (see Figs 62 (ii) The area of the sheet should be 1 m2, i.e., xy =¥110 mm . Hence, on 1.12 (a) and (b)). substitution of ratio, we have xx¥=21¥106 \=x 840. 896ª 841 yx2 1189. 2 1189 \= =ª Thus the basic size of a drawing sheet is 1189 mm (length) ¥ 841 mm (width). This size isUniversity designated as A0. A series of successive sizes are obtained by halving along the length or doubling along the width (see Figs 1.14 (a) and (b)). However, in any case the ratio of the sides of the sheet will maintain the ratio of 12: . The sizes of the drawing sheet as obtained are trimmed sizes. The untrimmed size of series of sheets will certainly be somewhat larger than the trimmed size. Designation of sheets with size, as per series ISO—A, is provided Fig. 1.11(a) & (b) Pencil compassOxfordin Table 1.5.

A3 841 A0 mm A2 594 A1 A1 420 A2 297 A3A4

A0 mm 0 210 420 594 841 1189 (a) (b) Fig. 1.12(a) & (b) Dividers Fig. 1.14(a) Halving & doubling Fig. 1.14(b) Sizes of drawing sheets

© Oxford University Press. All rights reserved. Introductory Concepts and BIS Conventions 7 Table 1.5 Sizes of drawing sheets Title Block Designation Untrimmed Size (mm) Trimmed Size (mm) Any technical drawing or related docu- Length Width Length Width ment must be provided with a title block A0 1230 880 1189 841 following the specification as per the A1 880 625 841 594 latest code of practice, i.e., IS:11665— A2 625 450 594 420 1985, conforming to ISO:7200—1984. A3 450 330 420 297 The title block should be positioned A4 330 240 297 210 in accordance with the recommendations of IS:10711—2001, conforming to ISO:5457—1999. The location of Untrimmed dimension the title block for the sheets positioned A0 to A3 size A4 size horizontally (sizes A0–A3) should be Trimmed dimension at the right-hand bottom corner and for Drawing space the sheets positioned vertically (sizes A4) should be at the shorter lower Title Block Title Block part (see Fig. 1.15). In both the cases, the direction of reading of drawing is same. The title block consists of one Pressor more adjoining rectangles, which Fig. 1.15 Placement of title block may be subdivided into boxes as per requirements (Fig. 1.16). It is mandatory to include the following three types of information in the title block: c (a) registration/identification number, b b b c (b) title of the drawing, and (c) name a a c a of the legal owner of the drawing. In addition, as per requirement, the other 170 max 170 max University170 max information that can be included would (a) (b) (c) be (d) symbol for the first-/third-angle projection, (e) main scale of the draw- Fig. 1.16 Contents of title block ing, (f) linear dimension unit, if other than millimetres, (g) surface texture 12 4 5 indication, and (h) geometrical toler- Oxford ances. Borders and Frame

3 As per the recommendations of 1 IS: 10711—2001 (conforming to ISO:5457—1999), the border should A be 20 mm wide on the left edge, in-

5 mm 10 mm cluding frame. All other borders 6 1Trimming mark should be 10 mm wide. The frame for 2Trimmed format drawing space should be drawn with 5mm 3 Grid reference border lines of 0.7 mm width (Fig. 1.17). 4 Frame of drawing space 20 mm 5 Drawing space Centring Marks 6 Untrimmed format During reproduction or for microfilm- Fig. 1.17 Borders and frames ing, four centring marks are placed

B Centring marks

Title block

Fig. 1.18 Centring marks and grid reference system Press

University

Fig. 1.19 Trimming marks Oxford at the ends of two axes of symmetry Grid Reference System of the trimmed sheet with symmetry For locating details, additions, or revisions easily, the entire sheet is divided tolerance 1 mm. These marks are indi- into fields. The fields are referenced along the vertical direction with uppercase cated with a 0.7 mm wide continuous alphabets, from top to bottom (except I and O). The horizontal fields are refer- line, starting at the grid reference bor- enced by numerals from left to right. The alphabets and numerals are placed in der and extending 10 mm beyond the the grid reference border marked X (see Fig. 1.18). Table 1.6 gives an account drawing frame (Fig. 1.18). of the number of fields against various paper sizes.

Table 1.6 Number of fields in the sheet Trimming Marks Size of sheet A0 A1 A2 A3 A4 In order to facilitate trimming of sheets, trimming marks are provided at the bor- Longer side 24 16 12 8 6 ders of the four edges. Each mark is in the form of two overlapping rectangles Shorter side 16 12 8 6 4 of dimensions 10 mm ¥ 5 mm (see Fig. 1.19).

Sheet Folding Pattern Lengthwise Fold size Cross Fold 130 109 190 190 190 190 190

247 1 Fold 9 Fold

(297) 8 Fold

297

7 Fold 6 Fold

5 Fold

4 Fold

3 Fold

2 Fold

146 (125) 190 190 190

1 Fold

(297) Press A1 6 Fold

297

5 Fold

4 Fold

3 Fold

2 Fold

116 (96) 96 96 190

6 Fold A2 (123) 1 Fold University

297

5 Fold 4 Fold 3 Fold 2 Fold

125 (105) 190

297

2 Fold 1 Fold Oxford

1.6 FOLDING OF DRAWING of practice, i.e., IS:11664—1986. The basic principles to be followed are as SHEETS follows: The drawing sheets must be folded (i) All sheets larger than A4 size should be folded to A4 size. properly and be kept either (i) in fold- (ii) Title blocks should appear in topmost position. ed or bound condition in a file or (ii) (iii) The bottom right corner should be the outermost visible section having a in a folded condition in a filing cabi- minimum width of 190 mm. net. The methods of folding must be The different types of folding patterns for either filing or keeping in a cabinet in accordance with the latest BIS code are shown in Tables 1.7 and 1.8, respectively.

Sheet Folding Pattern Lengthwise Fold size Cross Fold 139 (210) 210 210 210 210

7 Fold (247)

297 6 Fold

297

5 Fold 1 Fold

4 Fold

3 Fold

2 Fold

211 (210) 210 210

A1 4 Fold (297) Press

297

3 Fold 1 Fold

2 Fold

174 (210) 210

3 Fold A2 (123) University

297

2 Fold 1 Fold

(210) 210

297

1 Fold Oxford

1.7 DESCRIPTION OF DIFFERENT 20 and 21)—2001, conforming to ISO:128-20—1996 and ISO:128-21—1997. TYPES OF LINES The width (d) of any line should be constant throughout the length of the line. Depending on the type and size of drawing, the width of all types of lines will In technical drawing, a variety of be any of the following: lines, such as continuous, dashed, dotted, dash-dot type, etc., of different (i) A series of width based on a common ratio of 12: , i.e., 0.13, 0.18, widths are used. Each of the different 0.25, 0.35, 0.5, 0.7, 1, 1.4, or 2 mm. types of lines with various widths is (ii) Ratio of widths of narrow, wide, and extrawide lines should be 12::4 . indicative of different demarcation. The basic types of lines, with their designating number, are shown in Table 1.9. Let us now briefly discuss the various The different elements within a line, i.e., dots, gaps, and dashes, are provided aspects of lines in accordance with in some specific dimensions. Table 1.10 gives the dimensions of the different the latest BIS codes IS:10714 (Part line elements.

Line Description Representation No.

01 Continuous line 02 Dashed line 03 Dashed spaced line 04 Long-dashed dotted line 05 Long-dashed double-dotted line 06 Long-dashed triple-dotted line 07 Dotted line 08 Long-dashed short-dashed line 09 Long-dashed double short-dashed line 10 Dashed dotted line 11 Double-dashed dotted line Press 12 Dashed double-dotted line 13 Double-dashed double-dotted line 14 Dashed triple-dotted line 15 Double-dashed triple-dotted line

Table 1.10 Dimensions of line elements University Line No. Line Element Length Lines Used in Construction Drawing 04–07 and 10–15 Dot £ 0.5d Let us now discuss the different line 02 and 04–15 Gap 3d styles used in construction drawing 08 and 09 Short dash 6d of civil engineering. Normally, nar- 02, 03 and 10–15 Dash 12d row, wide, and extrawide lines are Oxford used, with the ratio of widths being 04–06, 08 and 09 Long dash 24d 1 : 2 : 4. The width of the line is cho- 03 Space 18d sen according to the line type (see Table 1.11). Table 1.12 lists the application of Table 1.11 Width of lines used for construction drawing different lines in construction drawing. Line Width (mm) Line Group Narrow Wide Extrawide Lines Used in Mechanical 0.25 0.13 0.25 0.5 Drawing 0.35 0.18 0.35 0.7 As in construction drawing, different line styles are also used in mechanical 0.5 0.25 0.5 1 drawing. Normally, two line widths are 0.7 0.35 0.7 1.4 used and the line widths are according 1 0.5 1 2 to the line type (see Table 1.13).

Line No. Subdivision of Line No. and Description Application of Lines

01 01.1 01.1.1 Boundaries of different materials in view Continuous Continuous Narrow Line 01.1.2 Hatching line 01.1.3 Diagonals for indication of openings, holes, and recesses 01.1.4 Arrow lines in stairs, ramps, and sloping areas 01.1.5 Modular grid lines, first stage 01.1.6 Short centrelines 01.1.7 Extension lines 01.1.8 Dimension lines and their terminators 01.1.9 Leader lines 01.1.10 Existing contours on landscape drawings 01.1.11 Visible outlines of parts in view 01.1.12 Simplified representations of doors, windows, stairs, fittings 01.1.13 Framing of details 01.1.14 Limits of partial or interruptedPress views (continuous narrow zigzag lines) Continuous Narrow Lines with Zigzags

01.2 01.2.1 Visible outlines of parts in cut and section when hatching is used Continuous Wide Line 01.2.2 Boundaries of different materials in view, cut, and section 01.2.3 Visible outlines of parts in view 01.2.4 Simplified representation of doors, windows, stairs, fittings, etc. 01.2.5 Modular grid lines, second stage 01.2.6 Arrow lines for marking of views, cuts, and sections University01.2.7 Proposed contours on landscape drawings 01.3 01.3.1 Visible outlines of parts in cut and section when hatching is not used Continuous Extra-wide Line 01.3.2 Reinforcing bars 01.3.3 Lines of special importance

02 02.1 02.1.1 Existing contours on landscape drawings Dashed line Dashed Narrow Line 02.1.2 Subdivision of plant bed or grass Oxford 02.1.3 Hidden outlines 02.2 02.2.1 Hidden outlines Dashed Wide Line 02.3 02.3.1 Reinforcing bars in bottom layer on plan and far face layer in elevation when bottom and top layers and near and far face layers are shown on the same Dashed Extra-wide Line sketch

04 04.1 04.1.1 Cutting planes Long-dashed Long Dashed Dotted Narrow Line 04.1.2 Centre lines dotted line 04.1.3 Lines of symmetry 04.1.4 Framing of enlarged details 04.1.5 Reference lines 04.1.6 Limits of partial or interrupted views, cuts, and sections

(Continued)

Line No. Subdivision of Line No. and Description Application of Lines 04.2 04.2.1 Cutting planes

Long Dashed Dotted Wide Line 04.2.2 Outlines of visible parts situated in front of the cutting plane

04.3 04.3.1 Secondary lines for setting out an arbitrary reference lines Long Dashed Dotted Extra-wide Line 04.3.2 Indication of lines of surfaces to which a special requirement applies 04.3.3 Boundary lines for contracts, stages, zones, etc. 05 05.1 05.1.1 Alternative and extreme positions of movable parts Long-dashed Long Dashed Double Dotted 05.1.2 Centroidal lines double-dotted Narrow Line 05.1.3 Outlines of adjacent parts line 05.2 05.2.1 Outlines of hidden parts situated in front of the cutting plane

Long Dashed Double Dotted Wide Line

05.3 05.3.1 Reinforcing prestressed bars and cables

Long Dashed Double Dotted Extra-Wide Line 07 07.1 07.1.1 Outlines of parts not included in the project Dotted line Dotted Narrow Line Press

Table 1.14 Application of different lines for mechanical drawing Table 1.13 Width of lines used for mechanical drawing Line Subdivision of Line No. and Description Application of Lines No. Line Width (mm) for Line No. Line 01.1 01.1.1 Imaginary lines of intersection Group 01.2, 02.2, 01.1, 02.1, 04.2 04.1, 05.1 Continuous Narrow Line 01.1.2 Dimension lines 01.1.3 Extension linesUniversity 0.25 0.25 0.13 01.1.4 Leader lines and reference lines 0.35 0.35 0.18 01.1.5 Hatching 0.5 0.5 0.25 01.1.6 Outlines of revolved sections 0.7 0.7 0.35 01.1.7 Short centre lines 01.1.8 Root of screw threads 1 1 0.5 Oxford01.1.9 Dimension line terminations 1.4 1.4 0.7 01.1.10 Diagonals for the indication of flat surfaces 2 2 1 01.1.11 Bending lines on blanks and processed parts

01 01.1.12 Framing of details 01.1.13 Indication of repetitive details Table 1.14 lists the application of dif- Continuous line 01.1.14 Interpretation lines of tapered features ferent lines in mechanical drawing.. 01.1.15 Location of laminations 01.1.16 Projection lines 1.8 PATTERNS OF LETTERING 01.1.17 Grid lines The pattern of lettering is a vital part 01.1.18 Preferably, manually represented termination of for the preparation of a complete tech- partial or interrupted views, cuts, and sections, if Continuous Narrow Freehand Line nical drawing. Writing of all texts in- the limit is not a line of symmetry or a centreline cluding numerical items of the draw- 01.1.19 Preferably, mechanically represented termination of partial or interrupted views, cuts, and sections, ing should be in accordance with the ContinuousContinous Narrow Narrow Lines withLines Zigzags if the limit is not a line of symmetry or a centreline general requirements as laid down with Zigzags in the latest BIS code IS:9609 (Part (Continued) 0)—2001, conforming to ISO:3098-

© Oxford University Press. All rights reserved. 14 Machine Drawing 0—1997. For numerically controlled Table 1.14 Application of different lines for mechanical drawing (Continued ) lettering, either of the two types, 01.2 01.2.1 Visible edges namely, ‘type A’ and ‘type B’, should be used. Each of these two types can Continuous Wide Line 01.2.2 Visible outlines be written either in a vertical fashion 01.2.3 Crests of screw threads or in an inclined fashion at an angle of 01.2.4 Limit of depth of full-depth thread 75° with the base line. Heights of all 01.2.5 Main representations in diagrams, maps, flow charts alphanumeric characters are defined 01.2.6 System lines by the proportion of the height of any 01.2.7 Parting lines of moulds in view uppercase alphabet. The height of the 01.2.8 Lines of cuts and section arrows uppercase alphabet is called nominal 02.1 02.1.1 Hidden edges size (h). The range of nominal sizes Dashed Narrow Line 02.1.2 Hidden outlines are in a series of ratio of 12: , such 02 02.2 02.2.1 Indication of permissible areas of surface treat-

as 1.8, 2.5, 3.5, 5, 7, 10, 14, and 20 Dashed line ment Dashed Wide Line mm. The line width (d) of any sort of character is constant and the spacing 04.1 04.1.1 Centrelines between successive characters will be Long Dashed Dotted Narrow Line 04.1.2 Lines of symmetry twice the line width. The intercharac- 04.1.3 Pitch circle of gears ter spacing for some specific combina- 04 04.1.4 Pitch circle of holes tion of alphabets, such as ‘LA’, ‘TV’, 04.2 04.2.1PressIndication of required areas of surface treatment ‘Tr’, etc., will only be the line width. Long Dashed Dotted Wide Line 04.2.2 Indication of cutting planes Long-dashed dotted line Different heights related to lettering 05.1 05.1.1 Outlines of adjacent parts are shown in Fig. 1.20. These dimen- 05.1.2 Extreme positions of movable parts sions in terms of nominal size (h) for Long Dashed Double Dotted 05.1.3 Centroidal lines letters of type A and type B are pro- Narrow Line vided in Table 1.15 05.1.4 Initial outlines prior to forming Some Latin alphabets, numerals, and 05 05.1.5 Parts situated in front of a cutting plane marks, both in vertical and inclined 05.1.6 Outlines of alternative executions style, in accordance with IS:9609 (Part University05.1.7 Outlines of the finished part within blanks 05.1.8 Framing of particular fields

1)—2006, conforming to ISO:3098- Long-dashed double-dotted line 2—2000, are shown in Fig. 1. 21. 05.1.9 Projected tolerance zone

Table 1.15 Relative dimensions for letters of type A and type B Characteristics Oxford Type A Type B Line width (d ) (1/14)h (1/10)h Height of uppercase letters (h) (14/14)h (10/10)h

Height of lowercase letters (c1) (10/14)h (7/10)h

Tail of lowercase letters (c2) (4/14)h (3/10)h

Stem of lowercase letters (c3) (4/14)h (3/10)h Height of diacritical marks (f ) (5/14)h (4/10)h Spacing between characters (a) (2/14)h (2/10)h

Minimum spacing between baselines [uppercase and lowercase with diacritical marks] (b1) (25/14)h (19/10)h

Minimum spacing between baselines [uppercase and lowercase without diacritical marks] (b2) (21/14)h (15/10)h

Minimum spacing between baselines [uppercase only] (b3) (17/14)h (13/10)h Spacing between words (e) (6/14)h (6/10)h

a e d c2 The basic methods of presentation of f h1 sectioned part of elements by means of b 1 hatching, in accordance with SP:46— Baseline 2003, are as follows: (i) The lines for hatching should be continuous narrow lines

c1 (e.g., line no. 01.1). (ii) The space between successive hatching lines should be pro- c3 portionate to the hatching area, b2 b3 Baseline but in no case should it be less than 0.7 mm (see Fig. 1.22).

Fig. 1.20 Dimensions for lettering Press

Fig. 1.22 Spacing between hatching lines

(iii) Hatching lines should be inclined preferably 45° to the principal outline of the area University (see Fig. 1.23 (a)) or 45° to the lines of symmetry of the area (see Figs 1.23 (b) and (c)).

Fig. 1.21(a) Letter type ‘A’, verticalOxford fashion Fig. 1.21(b) Letter type ‘B’, vertical fashion

(a) (b) (c)

Fig. 1.23 Basic pattern of hatching

(iv) For any large area, instead of hatching within entire area, hatching along the contour will be indicative (see Fig. 1.24). (v) In a case where sections of the same part in parallel planes are shown side by side, the hatch- Fig. 1.21(c) Letter type ‘A’, inclined fashion Fig. 1.21(d) Letter type ‘B’, inclined fashion ing should be identical but the

(a) (b)

Fig. 1.26 Interruption of hatching Fig. 1.27 Thin sections

propriate units of measurement and is indicated graphically with lines, sym- Fig. 1.24 Hatching of large area bols, and notes. All dimensional information, which is required to define a A-A component or part completely, should 25±0.06 15±0.01 be clearly shown within the technical drawing, unless mentioned in related Fig. 1.28 Functional dimension documents. The general system of dimensioning will be discussed here in accordance with the latest BIS code of practice, i.e., IS:11669—1986, conforming to ISO:129—1985. Broadly speaking,Press dimensioning is of two types:

A Functional Dimension These dimensions are very essential for the functioning of the element and for A the production of the drawing (see Fig. 1.28). Nonfunctional Dimension Fig. 1.25 Hatching in parallel sectional plane These dimensions are not essential for the functioning of the element.

lines in two parts should not be Basic Rules of Placement of Dimensions collinear. This convention is University followed for greater clarity (see The basic rules to be followed during dimensioning are as follows:. Fig. 1.25). (i) Dimensions should be placed on that particular view or on that particular section which most clearly shows the corresponding feature. (vi) In a case where inscribing di- (ii) Each feature should be dimensioned only once in a technical drawing. mension is inevitable within (iii) Within the drawing, all linear dimensions should be provided in the same the hatched area, lines of hatch- unit, preferably millimetres. Hence there is no necessity to write ‘mm’ at ing should be interrupted near Oxfordthe end of each dimension. Only one note, such as ‘all dimensions are zone of dimensions for better in millimetre’, placed at the end of the drawing sheet will be sufficiently clarity (see Fig. 1.26). indicative. If other units like ‘Nm’ or ‘MPa’ appear, dimensions should (vii) Thin sections should be shown be placed with proper mention of units. entirely in black (see Fig. 1.27 (iv) Functional dimensions, wherever possible, should be shown directly on (a)) and a gap of not less than the drawing. 0.7 mm should be maintained (v) Generally, the process of production or the method of inspection is not between adjacent thin sections mentioned within the drawing if not otherwise compelled for ensuring (see Fig. 1.27 (b)). satisfactory functioning or interchangeability. See Chapter 2 for a detailed discussion (vi) Nonfunctional dimensions should be placed in way that is most convenient of sectioning pattern. for inspection and production. 1.10 GENERAL SYSTEM OF Elements of Dimensioning DIMENSIONING The major elements of dimensioning, other than the dimension itself, are the The dimension of a technical drawing projection line, the dimension line, and the leader line. These are continuous is a numerical value expressed in ap- lines, and their code-specified conventions are as follows:

© Oxford University Press. All rights reserved. Introductory Concepts and BIS Conventions 17 (i) The projection line should be extended slightly beyond the respective drawn in an oblique pattern, but dimension line (see Figs 1.29 (a) and (b)). parallel to each other (see Fig. (ii) Generally, the projection lines are drawn perpendicular to the feature 1.30). being dimensioned. If it is found necessary, a projection line may be (iii) The indication of origin of a dimension line should be drawn as Leader line an open circle of approximately 2¥ 45° Projection line 3 mm diameter (see Fig. 1.31). Value of the dimension (iv) The dimension line should be terminated with an open

1500

3500 4500 arrow or closed arrow (filled or Origin indication Dimension line Termination (Arrowhead) unfilled) or an oblique stroke (a) inclined at 45° angle. The included angle of the arrowhead is variable from 15° to 90° (see Projection line Fig. 1.32). 4240 Value of the dimension (v) The dimension line should be shown unbroken for the feature Dimension line Termination (Oblique stroke) that is shown in broken line (b) (see Fig. 1.33). Press (vi) In principle, the projection line Fig. 1.29 Projection line, dimension line and leader line and the dimension line should not intersect each other. Where it is unavoidable, neither the projection line nor the dimension line should be shown with a break (see Figs 1.34 (a) and (b)). (vii) Arrowheads of the dimension University line generally terminate within Fig. 1.30 Oblique projection line Fig. 1.31 Origin indication of dimension line limits of projection line. In case of scarcity of space, the termination of arrowheads may be shown outside the intended limits of dimension line (see Oblique strokeOxford Figs 1.35 (a) and (b). Arrowheads System of Dimensioning Either of the following two systems is Fig. 1.32 Termination of dimension line Fig. 1.33 Unbroken dimension line followed in the placement style of dimensional values: 16 18

(a)

28 12

(a) (b) (b) Fig. 1.34 Projection line and dimension line Fig. 1.35 Arrowhead termination

© Oxford University Press. All rights reserved. 18 Machine Drawing System I In this system, the dimensional values are placed parallel to the 20 70 20 20 dimension line and preferably near the 20 20 middle, above, and clear of the dimension line. All indicated dimensional 30 20 20 39 values should be readable from the 20 20 bottom or the right-hand side of the 20 20 drawing (see Fig. 1. 36). 20

System II In this system, only the (a) (b) non-horizontal dimensional values are inserted within the dimension line. 60° 60° The horizontal dimensional values are 30° 30° placed parallel to the dimension line 60° 60° and preferably near the middle, above, and clear of the dimension line. All 60° 60° 30° 30° indicated dimensional values should be readable from the bottom only 60° 60° (see Fig. 1.37). 60° 60° Press (c) (d) Arrangement of Dimensions Fig. 1.36 Dimensioning as per System I The arrangement of dimensioning on a drawing clearly indicates the purpose of the design. Following are the different types of arrangements: f30 f20 f50 Chain dimensioning This arrangement of dimensioning is used only University where possible accumulation of toler- 60° 26 10 ances does not affect the functional re- 30° quirements of the part (see Fig. 1.38 for 75 60° (a) details). 60° 70 Dimensioning from a common 30° feature This arrangement isOxford used where a number of dimensions of the 30 60° 60° same direction relate to a common 39 feature. When a number of paral- (c) lel dimension lines with dimensional (b) values are used, it is called parallel Fig. 1.37 Dimensioning as per System II dimensioning (see Fig. 1.39). To sim- plify this process, sometimes we use superimposed running dimensioning 100 (see Figs 1.40 (a) and (b)). Often it is advantageous to use superimposed 150 running dimensioning in two direc- 160 420 tions (see Fig. 1.41). 160 70 200 30 640 Dimensioning by coordinates Sometimes dimensioning indicated Fig. 1.38 Chain dimensioning Fig. 1.39 Parallel dimensioning

15.5

160 150 420 640 15.5 15.5 0 11 0 150 420 640 120 26 (a) (b) 90 Fig. 1.40 Superimposed running dimensioning 13.5 26 60

13.5 13.5 13.5 20 0 X =70 Y =80 02060 100 140 180 200 X =20 Fig. 1.41 Superimposed running dimensioning in two Y =60 directions

1 XYf X =80 1 20 160 15.5 Y =40 3 2 20 20 13.5 3 60 120 11 Press X =10 (a) 5 4 60 60 13.5 by coordinates, with or without tabu- 5 100 90 26 lated explanation, are found to be very 3 4 6 XY 7 convenient. Various patterns of this 8 1 10 20 Y 2 procedure are shown in Fig. 1.42. 4 28040 9 37080 10 42060 0 Combined dimensioning Although 0 X 2 (c) not recommendable, if necessary, chain dimensioning, single dimension, 1 (b) University and dimensioning from a common feature can be combined (see Fig. 1.43). Fig. 1.42 Dimensioning by coordinates Special Indications in Dimensioning For proper identification of shape Oxford and improvement of interpretation of drawing, the following types of special symbols and indications are pro- (a) vided:

Symbols The uppercase alphabets ‘R’ and ‘SR’ indicate radius and spherical radius, respectively. f and Sf stand for diameter and spherical diameter, respectively. Sometimes a square symbol is used. The applications are explained pictorially in Fig. (b) 1.44. Chords, arcs, and angles can be shown unambiguously with symbols Fig. 1.43 Combined dimensioning as shown in Fig. 1.45.

SR12 100

Chord (a)

SR60 (a)

R15 R10 105 (d)

S5f 0 Arc

(b) (b)

42°

Angle (c) (e) Press (c) Fig. 1.44 Use of symbols in dimensioning Fig. 1.45 Special indication in dimensioning

15 51¥ 8(=90)

(a) 5¥ 10° (= 50°) University (a)

15 17¥ 18(=306) 50 Oxford(b) 9 Fig. 1.46 Equidistant linear dimensioning

Equidistant features When equi- (b) distant features or uniformly arranged elements are available on a drawing, Fig. 1.47 Equidistant angular dimensioning dimensioning system may be simplified. Simplified linear spacing and 1.11 CONVENTIONAL REPRESENTATION OF THREADS AND angular spacing are illustrated in Figs THREADED PARTS 1.46 and 1.47, respectively. In this section, we will discuss the conventional representation of threads and threaded parts in accordance with the latest BIS code of practice, i.e., IS:10715 Repeated features If it is possible (Part 1)—1999, conforming to ISO:6410-1—1993. to define a quantity of elements of the same size so as to avoid repeating the Representation of Single Entity same dimensional value, they may be In the side view and the section of visible screw threads alone, the crests should shown as depicted in Fig. 1.48. be drawn with a continuous wide line (e.g., line no. 01.2) and the roots with a

© Oxford University Press. All rights reserved. Introductory Concepts and BIS Conventions 21 8 (or¥ f 8 holes8 8) f continuous narrow line (e.g., line no. 01.1) (see Fig. 1.49). At the end view, the roots of the thread are represented with a three-quarters circle, open at the top right quadrant. The circle is drawn with a continuous narrow line (e.g., line no. 01.1). These are illustrated in Figs 1.49 and 1.50. When it is neces- (a) sary to show hidden screw threads, the crests and roots are represented by 45° 6 (or¥ f 6 holes8 8) f dashed narrow line (e.g., line no. 02.1) (see Fig. 1.51).

60° Representation of Assembled Parts The conventions as followed for sin- 60° 45° gle entity are equally applicable for 60° assembled threaded parts. The exter- Pressnally threaded parts should always be Fig. 1.48 Repeated feature dimensioning shown covering the internally threaded parts and without any hidden lines. The wide line representing the limit of the useful length of the internal screw thread should be drawn to the root of the internal thread (see Fig. 1.52).

Fig. 1.49 Continuous boundary of visible screw thread University

or Oxford

Fig. 1.52 Assembled threaded part

End view of screw thread Fig. 1.50 Designation and Dimensioning of Threaded Parts Generally, a few alphanumeric characters are used to designate the threads. First, the kind of thread is mentioned with abbreviated alphabets, such as M (for metric thread), G (for one type of British Standard Pipe thread), HA, Tr, etc. The nominal diameter is written just after the type of thread. Sometimes the lead (L) and pitch (P) Fig. 1.51 Hidden screw thread are mentioned in millimetres. For the

Short thread engagement d 1.5 mm pitch 3mm lead b 20 mm nominal diameter Metric thread (a) (a)

M20 ¥ 2–6G/6h –LH

Left-hand threads d Tolerance class 2mm pitch

20 mm nominal diameter Metric thread (b) (b)

Fig. 1.54 Dimensioning of screw thread Fig. 1.53 Designation of screw thread Press right-hand threads, the direction of lead need not be mentioned. But for the left-hand threads, the direction of lead must be mentioned with ‘LH’. If required, the tolerance information is also provided within the designation of the thread. As per the requirement, Cylindrical helical Conical helical Cylindrical helical with square c/s the thread engagement type (N, nor- University mal; S, short; L, long) may need to be Fig. 1.55(a) Sectional views of some helical compression springs mentioned. See Figs 1.53 (a) and (b) for a better understanding. Regarding dimension, the nominal diameter (d) refers to the crest of the external thread or the root of the internal thread. The thread length (Oxfordb) normally refers to the length of the full- Cylindrical helical Conical helical Cylindrical helical depth thread (see Fig. 1.54). with square c/s Fig. 1.55(b) Simplified presentation of Fig. (a) 1.12 CONVENTIONAL REPRESENTATION OF SPRINGS Helical Compression Springs The conventional simplified repre- These springs are of two types, namely, cylindrical helical compression spring sentation of compression springs, ex- and conical helical compression spring. The cross section may be circular or tension springs, torsion springs, disc noncircular. When it is noncircular type, a small square or a small rectangle springs, spiral springs, and leaf springs will have to be provided as a symbol to indicate the cross section square type are briefed here in accordance with or rectangular type, respectively. The helix of the spring is considered as right- the latest BIS code of practice, i.e., hand type, by default. If it is left-hand type, then it is to be specified with ‘LH’. IS:10716 (Part 1)—1999, conforming Figures 1.55 (a) and (b) represent the sectional views and simplified presenta- to ISO:2162-1—1993. tion, respectively, of some helical compression springs.

Sectional View

Sectional view Simplfied view View Simplified View

Fig. 1.56 Helical extension spring Fig. 1.57 Torsion springs

Sectional and simplfied view of single disc spring View and simplfiedPress view of spiral with rectangular c/s

Sectional and simplfied view of multi-disc spring View and simplfied view of constant force spiral extension spring

Fig. 1.58 Disc springs Fig. 1.59 Spiral springs University tional and simplified views of some View and simplfied view of laminated leaf spring without eyes torsion springs are represented in Fig. 1.57. Oxford Disc Springs The sectional and simplified views of View and simplified view of laminated leaf spring with eyes some disc springs are represented in Fig. 1.58. Fig. 1.60 Leaf spring

Spiral Springs Helical Extension Springs The sectional and simplified views of In these springs, the requirements for the indication of cross section and some spiral springs are represented in direction of helix are identical to that of helical compression springs. The sec- Fig. 1.59. tional and simplified views of some helical extension springs are represented in Fig. 1.56. Leaf Springs Torsion Springs The sectional and simplified views of In these springs, the requirements for the indication of cross section and di- some leaf springs are represented in rection of helix are identical to that of helical compression springs. The sec- Fig. 1.60.

© Oxford University Press. All rights reserved. 24 Machine Drawing 1.13 CONVENTIONAL REPRESENTATION OF GEARS Let us now discuss the conventional representation of gears in accordance with the latest BIS code of practice, i.e., IS:10717—1983, conforming to (a) ISO:2203—1973. (a) Contours Figure 1.61 represents the contours and edges of each gear, as if (a) in an unsectioned view, a solid gear bounded by tip surface, (b) in axial section, a (c) spur gear having two diametrically op- posite teeth, represented unsectioned, (b) and (c) even in case of a gear without (b) spur teeth or with an odd number of Fig. 1.61 Contours and pitch indications in Fig. 1.62 Root surface and teeth indications teeth. gears Pressin gears Pitch show in unsectioned view, it can be The pitch is indicated with a pitch shown with a continuous narrow line circle with long dashed dotted narrow (see Fig. 1.62). line, when the view is normal to the Right helical Left helical axis. In case of a projection parallel to Teeth the axis, the pitch is indicated by its The profile of teeth must be speci- apparent contour, by means of extend- fied with reference to a standard or by ing the line beyond the gear contour a drawing. If it is essential to show Double helical Spiral on each side (see Fig. 1.61). one or twoUniversity teeth on the drawing, these Fig. 1.63 Indications of direction of teeth in should be drawn with a continuous gears Root Surface wide line (see Fig. 1.62). It is vital to Generally, root surface is indicated in indicate the direction of teeth. Normally, teeth are symbolically indicated with sectional views. If really necessary to three continuous narrow lines as shown in Fig. 1.63.

Oxford RECAPITULATION · In India, the boards used for drawing are made as per the speci- conforming to ISO:3098-0—1997. fications of IS:1444—1989. · Latin alphabets, numerals, and marks, both in vertical and in- · The scale of drawing is the ratio of linear dimension of an object clined style, should follow IS:9609 (Part 1)—2006, conforming to represented in original drawing to real linear dimension of the ISO:3098-2—2000. object itself. The choice of scale should be in accordance with · The basic methods of presentation of sectioned part of elements IS:10713—1983, conforming to ISO:5455—1979. by means of hatching should follow SP:46—2003. · The size and layout of preprinted drawing sheets follows IS: · The general system of dimensioning should be done in accor- 10711—2001, conforming to ISO:5457—1999 and SP:46—2003. dance with IS:11669—1986, conforming to ISO:129—1985. · The title block of a drawing sheet should be as per IS:11665— · The conventional representation of threads and threaded parts 1985, conforming to ISO:7200—1984. should be done in accordance with IS:10715 (Part 1)—1999, · The folding of drawing sheets for preservation should be done in conforming to ISO:6410-1—1993. accordance with IS:11664—1986. · The conventional simplified representation of different types · The use of a variety of lines in technical drawing should be as springs should be in accordance with IS:10716 (Part 1)—1999, per IS:10714 (Part 20 and 21)—2001, conforming to ISO:128- conforming to ISO:2162-1—1993. 20—1996 and ISO:128-21—1997. · The conventional representation of gears should follow · All texts including numerical items of the drawing should follow IS:10717—1983, conforming to ISO:2203—1973. the general requirements as laid down in IS:9609 (Part 0)—2001,

MULTIPLE-CHOICE QUESTIONS

Pick out the best possible alternative(s). 14. As per the BIS code of specification, maximum width of the title block will be 1. What was the year of the latest revision of special publication no. (a) 190 mm (b) 180 mm 46 (SP:46) published by BIS? (c) 175 mm (d) 170 mm (a) 2003 (b) 1972 (c) 2010 (d) 2005 15. All larger size drawing sheets should be folded, following the BIS code of practice, into a size of 2. What are the dimensions of D1 type drawing boards as per IS (a) A4 (b) B4 specification? (c) A2 (d) foolscap size (a) 1525 ¥ 1220 (b) 920 ¥ 650 (c) 1270 ¥ 920 (d) 500 ¥ 350 16. As per the guidelines of BIS, the specific ratio to be maintained for the widths of narrow, wide, and extrawide lines is 3. Parallel lines can be drawn with (a) 1:2:4 (b) 1:2:3 (a) T-square only (b) T-square and/or set-square (c) 1: 1.5:2.5 (d) 10:11:12 (c) set-square only (d) divider 17. Which of the following types of lines is used as the dimension 4. Which of the following equipments are used for drawing curves of line? different radii? (a) continuous narrow line (b) continuous wide line (a) French curves (b) set-square (c) continuous extrawide line (d) dotted narrow line (c) T-square (d) protractor 18. Which of the following types of lines is used in hatching? 5. Drafting machine can draw (a) continuous narrow line (a) parallel lines (b) perpendicular lines (b) long-dashed dotted wide line (c) lines at any angle (d) curves of different radii (c) continuous extrawidePress line 6. X:1 represents (d) dashed wide line (a) a reduction scale (b) a full-size scale 19. Which of the following types of lines is used as hidden outlines? (c) a comparative scale (d) an enlargement scale (a) hidden narrow line (b) long-dashed dotted wide line 7. 1:X represents (c) continuous extrawide line (a) an enlargement scale (b) a full-size scale (d) hidden wide line (c) a comparative scale (d) a reduction scale 8. 1:1 represents 20. Which of the following types of lines is used as leader lines? (a) a full-size scale (b) an enlargement scale (a) hidden narrow line (c) a comparative scale (d) a reduction scale (b) long-dashed dotted wide line (c) continuous narrow line (d) hidden wide line 9. What is the area of trimmed A0 size drawing sheet? University (a) 1.5 m2 (b) 2.0 m2 21. Which of the following types of lines is used as leader lines? (c) 0.1 m2 (d) 1 m2 (a) hidden narrow line (b) long-dashed dotted narrow line 10. State the correct ratio of length to width of any trimmed drawing (c) continuous narrow line sheet conforming to the BIS code of practice (d) hidden wide line (a) 12: (b) 1:1 22. What is the preferable inclination of hatching lines? (c) 21: Oxford(d) 32: (a) 30 (b) 60 11. As per the BIS code of practice, which of the following information (c) 75 (d) 45° is mandatory for the title block? 23. What is the possible angle included within the arrowhead of a (a) the main scale of the drawing dimension line? (b) the surface texture indication (a) 30 (b) 60 (c) geometrical tolerances (c) 45 (d) all of these (d) the title of the drawing 24. What does ‘SR’ indicate in dimensioning? 12. The line width used to draw the frame-enclosing space of drawing in a standard trimmed drawing sheet is (a) spherical radius (b) simple radius (a) 0.7 mm (b) 0.8 mm (c) separated diameter (d) short radius (c) 0.9 mm (d) 1 mm 25. What does the alphabet ‘M’ stand for the conventional represen- 13. How many number of drawing fields bounded by grid lines are tation of threads? there in an A4 size trimmed drawing sheet? (a) pitch expressed in millimetre (a) 36 (b) 30 (b) lead expressed in millimetre (c) 24 (d) 20 (c) multiple thread (d) metric thread

ANSWERS 1. (a) 2. (b) 3. (b) 4. (a) 5. (a), (b), and (c) 6. (d) 7. (d) 8. (a) 9. (d) 10. (c) 11. (d) 12. (a) 13. (c) 14. (d) 15. (a) 16. (a) 17. (a) 18. (a) 19. (a) and (d) 20. (c) 21. (b) 22. (d) 23. (d) 24. (a) 25. (d)

REVIEW QUESTIONS 1. Explain in detail the methodology for deriving the basic size of 6. What are the basic rules to follow for the placement of dimen- trimmed drawing sheets. sions in a technical drawing? 2. Write short notes on (i) enlargement scale and (ii) reduction 7. What are two systems of dimensions generally followed? scale. 8. Explain the different types of arrangements of dimensions. 3. What is the utility of a title block in a drawing? 9. Draw the examples of simplified representation of helical springs 4. State the basic principles of sectioning in brief. and leaf springs. 5. Differentiate between the functional dimension and the nonfunctional dimension. Press

University

Oxford