(As per New Revised Syllabus of Anna University) Department of Mechanical Engineering. SATHYABAMA UNIVERSITY Jeppiaar Nagar, Chennai

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1 (1*,1((5,1* *5$3+,&6 (As per New Revised Syllabus of Anna University) Dr. S.RAMACHANDRAN, M.E., Ph.D. Professor & Head K. PANDIAN, M.E., E.V.V.RAMANAMURTHY, M.Tech., R. DEVARAJ, M.E., Associate Professors Department of Mechanical Engineering SATHYABAMA UNIVERSITY Jeppiaar Nagar, Chennai AIR WALK PUBLICATIONS (Near All India Radio) 80-A, I Floor, Karneeshwarar Koil Street, Mylapore, Chennai Ph.: , aishram2006@gmail.com

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3 ANNA UNIVERSITY GE6152 ENGINEERING GRAPHICS Concepts and Conventions (Not for Examination) 1 Importance of graphics in engineering applications Use of drafting instruments BIS conventions and specifications Size, layout and folding of drawing sheets Lettering and dimensioning. UNIT I Plane Curves and Free Hand Sketching 5+9 Basic Geometrical constructions, Curves used in engineering practices: Conics Construction of ellipse, parabola and hyperbola by eccentricity method Construction of cycloid construction of involutes of square and circle Drawing of tangents and normal to the above curves, Scales: Construction of Diagonal and Vernier scales. Visualization concepts and Free Hand sketching: Visualization principles Representation of Three Dimensional objects Layout of views- Free hand sketching of multiple views from pictorial views of objects UNIT II Projection of Points, Lines and Plane Surfaces 5+9 Orthographic projection- principles-principal planes-first angle projection-projection of points. Projection of straight lines (only First angle projections) inclined to both the principal planes -Determination of true lengths and true inclinations by rotating line method and traces Projection of planes (polygonal and circular surfaces) inclined to both the principal planes by rotating object method. UNIT III Projection of Solids Projection of simple solids like prisms, pyramids, cylinder, cone and truncated solids when the axis is inclined to one of the principal planes by rotating object method and auxiliary plane method. UNIT IV Projection of Sectioned Solids and Development of Surfaces 5+9 Sectioning of above solids in simple vertical position when the cutting plane is inclined to the one of the principal planes and perpendicular to the other obtaining true shape of section. Development of lateral surfaces of simple and sectioned solids Prisms, pyramids cylinders and cones. Development of lateral surfaces of solids with cut-outs and holes UNIT V Isometric and Perspective Projections Principles of isometric projection isometric scale Isometric projections of simple solids and truncated solids - Prisms, pyramids, cylinders, cones- combination of two solid objects in simple vertical positions and miscellaneous problems. Perspective projection of simple solids-prisms, pyramids and cylinders by visual ray method. Computer Aided Drafting (Demonstration Only) 3 Introduction to drafting packages and demonstration of their use. TOTAL: 75 PERIODS

4 UNIT I JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY I Year B.Tech. M.E. ENGINEERING GRAPHICS Introduction to Engineering Drawing: Principles of Engineering Graphics and their Significance Drawing Instruments and their Use Conventions in Drawing Lettering BIS Conventions. Curves used in Engineering Practice & their Constructions : (a) Conic Sections including the Rectangular Hyperbola General method only. (b) Cycloid, Epicycloid and Hypocycloid (c) Involute. (d) Helices UNIT II Drawing of Projections or Views Orthographic Projection in First Angle Projection Only : Principles of Orthographic Projections Conventions First and Third Angle Projections Projections of Points and Lines inclined to both planes, True lengths, traces. UNIT III Projections of Planes & Solids : Projections of regular Planes, auxiliary planes and Auxiliary projection inclined to both planes. Projections of Regular Solids inclined to both planes Auxiliary Views. Sections and Sectional views of Right Regular Solids Prism, Cylinder, Pyramid, Cone Auxiliary views. UNIT IV Development and Interpenetration of Solids: Development of Surfaces of Right Regular Solids Prisms, Cylinder, Pyramid Cone and their parts. Interpenetration of Right Regular Solids Intersection of Cylinder Vs Cylinder, Cylinder Vs Prism, Cylinder Vs Cone. UNIT V Isometric Porjections : Principles of Isometric Projection Isometric Scale Isometric Views Conventions Isometric Views of Lines, Plane Figures, Simple and Compound Solids Isometric Projection of objects having non- isometric lines. Isometric Projection of Spherical Parts. UNIT VI Transformation of Projections: Conversion of Isometric Views to Orthographic Views Conventions. UNIT VII Perspective Projections: Perspective View : Points, Lines, Plane Figures and Simple Solids, Vanishing Point Methods (General Method only). UNIT VIII Introduction to Computer aided Drafting: Generation of points, lines, curves, polygons, simple solids, dimensioning.

5 CONTENTS CONCEPTS AND CONVENTIONS 1. Introduction Importance of graphics in engineering applications Use of drafting instruments BIS conventions and specifications Size, layout and folding of drawing sheets Lettering and dimensioning UNIT 1 PLANE CURVES AND FREE HAND SKETCHING 2. Basic Geometrical Constructions and Conic Sections Curves used in engineering practices: Conics Construction of ellipse, parabola and hyperbola by eccentricity method Construction of cycloid construction of involutes of square, pentagon and circle - Drawing of tangents and normal to the above curves. Scales: Construction of Plain, Diagonal and Vernier Scales ORTHOGRAPHIC PROJECTIONS Visualization concepts and Free Hand sketching: Visualization principles, Orthographic projection Principles-Principal planes-first angle projection -Representation of Three Dimensional objects Layout of views. Sketching of Orthographic views from given Pictorial views of objects Sketching of Pictorial views from given orthographic projections FREE HAND SKETCHING Free hand sketching of multiple views from pictorial views of objects UNIT II PROJECTIONS OF POINTS, LINES AND PLANE SURFACES 4. Projections of Points Projections of Straight lines Projection of straight lines (only First angle projections) inclined to both the principal planes -Determination of true lengths and true inclinations by rotating line method and traces

6 6. Projections of Plane Surfaces Projection of planes (polygonal and circular surfaces) inclined to both the principal planes by rotating object method UNIT III PROJECTIONS OF SOLIDS 7. Projection of simple solids like prisms, pyramids, cylinder, cone and truncated solids when the axis is inclined to one of the principal planes by rotating object method (change of position method) and auxiliary plane method (change of reference plane method) UNIT - IV PROJECTION OF SECTIONED SOLIDS AND DEVELOPMENT OF SURFACES 8. Section of solids Sectioning of solids in simple vertical position when the cutting plane is inclined to the one of the principal planes and perpendicular to the other obtaining true shape of section Development of surfaces Development of lateral surfaces of simple and sectioned solids prisms, pyramids, cylinders and cones. Development of lateral surfaces of solids with square and cylindrical cutouts and holes perpendicular to the axis UNIT - V ISOMETRIC AND PERSPECTIVE PROJECTIONS 10. Isometric projection Principles of isometric projection isometric scale isometric projections of simple solids, truncated solids- prisms, pyramids, cylinders and cones-combination of two solid objects in simple vertical positions and miscellaneous problems Perspective projection Perspective projection of simple solids-prisms, pyramids and cylinders by Visual ray method and Vanishing point method Computer Aided Drafting: (Demonstration only) Auto cad Introduction to drafting packages and demonstration of their use ANNA UNIVERSITY SOLVED QUESTION PAPERS

7 Introduction INTRODUCTION Engineering drawing is the graphical language of Engineers. It is a graphical representation of thinking and planning of ideas in a systematic manner. It is an indispensable tool in an engineers occupation. It helps them to communicate their thoughts and ideas graphically in a neat fashion. The preliminary step in the design of almost any component manufactured in an industry, involves drafting (drawing) on paper. This is because of the fact that, drawings and sketches help to improve the design and feasibility of the manufacturing components. The accuracy and neatness of the drawings depend mostly on the quality of instruments used. Good quality instruments go a long way in helping students to prepare drawings easily and quickly. A thorough knowledge of using drawing instruments, materials and drawing techniques will help the students to create accurate and neat drawings. Nowadays, the advent of Computer Aided Design (CAD) provides a neat diagram with greater accuracy and speed. Therefore, it is important for an engineering student to practice Engineering Drawing as this is a necessary skill he has to master in order to be a successful Engineer. Drawing instruments and materials Drawings are made by means of various simple and quality instruments. The quality of drawing depends on the quality and accuracy of the drawing instruments. Therefore, students must have thorough knowledge of using the drawing instruments used. Each student must have the following set of drawing instruments and materials. 1. Drawing board 2. Drawing sheets 3. Pencils 4. Eraser - Erasing shield 5. Drawing pins, clips and tapes 6. Set squares 7. Drafting machine or Mini-drafter. 8. Instrument box (a) Large compass (b) Bow compass (c) Dividers (d) Leads 9. Protractor 10. French curves

8 1.2 Engineering Graphics Circle master 12. Pencil sharpener. Drawing Board Drawing board is rectangular in shape and is made from best seasoned timber and soft wood of yellow pine. The top surface of the wood must be perfectly flat and free from warping. The dimensions of board are related to the sizes of drawing sheets. Drawing sheets are fixed to it by pins, clips or adhesive tapes. The standard sizes of drawing boards according to IS are given below. Sl.No. Designation Size of drawing sheets Size (mm) of boards length breadth thickness 1. B 0 A B 1 A B 2 A B 3 A B 4 A The drawing board with designation B 2 is generally used for class room work. The drawing board with designation B 0 is used in design department of industries. Drawing sheets Normally white papers of good quality drawing sheets are used. Cartridge or machine made paper is most suitable for drawing sheets. IS: has recommended the following sizes of drawing sheets. Sl.No. Designation Trimmed size in mm. 1. A A A A A

9 Introduction 1.3 Drawing sheets are fixed to the drawing board by clips, drawing pins or adhesive tapes. Generally, A 2 size drawing sheets are used in first year engineering drawing practice. Different sizes of drawing sheets are shown below. Pencils The accuracy and neatness of the drawing depends on the type of quality pencils used. The grades of pencils are made in a range from 9H (hardest) to 7B (softest). The grade of

10 1.4 Engineering Graphics - the pencil is decided by the amount of graphite mixed with clay. The grade B,2B,3B... etc indicate the degree of softness in an increasing order. The grade H, 2H, 3H... etc indicate the degree of hardness in an increasing order. The following pencils are used in Engineering drawing practice. HB - Border lines, free hand sketching, Title block, arrow heads, Lettering, object lines and numbering. H - Dimension lines, section lines and centre lines etc. 2H - Projection lines, Extension lines, Construction lines, etc. Working with Pencil The pencil should be gripped at an approximate distance of 35 mm from the lead tip. The inclination of the pencil with the paper plays an important role in the quality of lines. The pencil is usually held inclined at about 60 with the paper. Eraser - Erasing shield Good quality soft rubber is most suitable for removing unwanted lines in pencil drawings. The erasing shield is used for erasing unwanted lines while protecting other lines. Drawing clips, pins and adhesive tape Drawing clips, pins and adhesive tape are used to fix drawing paper/sheet on the drawing board. Drawing clips are used to clamp drawing sheet corners along drawing board edges. To fix the corners of the sheet on the surface of the board, we use drawing pin, or adhesive tape. Pins pierce the sheet and the board creating holes on them. Adhesive tapes are

11 Introduction 1.5 free from this drawback. A crepe paper adhesive tape is recommended as it does not scratch the paper when removed for plastic adhesive tape, a paper piece may be kept between the sheet and the tape to avoid sticking of the tape to the sheet. Set-squares The set squares are made of celluloid transparent plastic material. They are available in the shape of triangles with two edges at right angle. Two types of set-squares are generally used and are 45 set-squares and set-squares. Parallel straight lines, vertical lines and inclined lines at 15, 30, 45, 60, 75, 90, 105 can be drawn by set-squares. Mini Drafter (or) Drafting Machine A mini drafter is a multipurpose machine. A miniature of drafting machine is mini drafter. It combines the advantages of the T - squares, set squares, scales and the protractor. Its one end is fixed by means of a clamp on the drawing board. At its other end, an adjustable

12 1.6 Engineering Graphics - protractor marking is fitted. The two engraved scales are accurately set at right angle to each other and it is attached to the protractor markings. The blades can be set at any desired angle with the help of protractor markings. Mini - drafter is most commonly used by the students and draughts man. An error free mini drafter is essential for good drawings. Instrument Box Compass or large bow The compass is used for drawing circles and circle arcs. It consists of two legs hinged together at top end. A pointed needle is fitted at the lower end of one leg, while a pencil lead is inserted at the end of the other leg. Circles of more than 150 mm radius are drawn with the aid of the lengthening bar. The lower part of the pencil leg is detached and the lengthening bar is inserted in its place, thus increasing the length of the pencil leg. For drawing small circles and arcs of less than 25 mm radius, small bow compass is used. Dividers The dividers are similar to the compass in construction. The divider has two legs hinged at the top end and is provided with steel points at both the lower ends.

13 Introduction 1.7 The dividers are used 1. To divide curved or straight lines into desired number of equal parts. 2. To transfer dimensions from one part of the drawing to another part. Small bow divider is used for marking minute divisions and large number of short equal distances.

14 1.8 Engineering Graphics - Protractors Protractor is commonly used in engineering drawing offices. It is a semi-circular one in which the angles are marked from 0 to 180 and is usually made of plastic. Sand papers It is used for sharpening the pencil. The pencil should be moved on full length as shown in fig. French curves French curves are used to draw irregular curves which cannot be drawn by compass. Irregular curves are either drawn by free hand or with French curves. They are made of wood or plastic. The edges of the French curves must be perfectly smooth. Fig. shows some of the French curves.

15 Introduction 1.9 Circle Master It consists of circles of different sizes. It is a flat piece made of plastic. Line marks are marked over it for adjusting the circle master with the two axes (horizontal and vertical). It reduces the drafting time. Layout of drawing sheet A border line is usually drawn around a sheet as shown in fig. using HB pencil. It is drawn at a distance 20 mm from left hand side and 10 mm from the other three sides. The left side 20 mm is given for filing and binding purposes. Border line is a thick darkened line which serves as a frame for the drawing sheet.

16 1.10 Engineering Graphics - Folding of Drawing sheet (IS: ) Drawing sheets are folded for filing and binding purposes. The recommended folding for A2 drawing sheet is shown in fig. The basic principles in folding of drawing sheets are (i) all larger size drawing sheets ie. A 0, A 1, A 2 and A 3 are folded to A 4 size sheet.

17 Introduction 1.11 (ii) (iii) the title block of the folded sheets must be the bottom most position. the bottom right corner should be the outer visible section and should be a width of not less than 190 mm. TITLE BLOCK It is an important feature of drawing. It should be placed at the bottom right corner of the drawing sheet. The recommended specifications as per IS: provides the following information. 1. Name of the student preparing drawing 2. Roll No. 3. Section 4. Title of drawing 5. Drawing sheet number 6. Scales 7. Name of the institution or firm 8. Date 9. Symbol denoting the method of projection 10. Name of the office checking the drawing A typical recommended title - block is shown in fig. TYPES OF LINES For better understanding of any object, it is essential to differentiate the various types of lines. (ie.,) object lines, reference lines, leader lines, dimension lines etc. Some conventions are used to differentiate the above lines while drawing. The types of lines recommended by IS: are shown in Table.

18 1.12 Engineering Graphics - Line Description Applications Continuous thick (H) Visible outlines Visible edges Continuous thin (2H) (Straight or curved) Continuous thin free hand (2H) Continuous thin (straight) with zigzags. (2H) Imaginary lines of intersection, dimension lines, projection lines, leader lines, hatching, outlines of revolved section, short centre lines. Limits of partial or interrupted views and sections, if the limit is not a chain thin line do Dashed thick (H / 2H) Dashed thin Chain thin (2H) Hidden outlines, Hidden edges do Centre lines Lines of symmetry Trajectories Chain thin, thick at ends and changes of direction (H) Chain thick (H) Chain thin double dashed. (2H) Cutting planes Indication of lines or surfaces to which a special requirements applies. Outlines of adjacent parts, alternative or extreme positions of movable parts, centroidal lines, initial outlines prior to forming, parts situated in front of the cutting plane.

19 Introduction 1.13 Object line (Use HB pencil) Dark It is the line used for showing the model or object of interest. This line should be comparatively dark enough to show the model or object. It is a continuous thick line drawn by HB pencil. Hidden line (Use HB pencil) Dark It is the line used for showing the edges of the object that are not visible from the view point. These line should be drawn as thick line consisting of short dashes, which are evenly placed. Centre line (Use H pencil) Medium Dark It is the line used for showing the axis of the solid and also centre location. This line should be drawn as long and short dashes closely and evenly placed. Construction line (Use 2H pencil) Light It is a thin line used for developing and formulating the ideas in order to get final object. This line should be drawn using 2H pencil. Border lines (Use HB pencil) Dark These lines are used to denote the frame of the drawing sheets. These lines are used to ensure that drawings are drawn within the frame work. This lines should be continuous, 0.5 mm thick line drawn by HB pencil. Projection lines (Use 2H pencil) Light Projection lines are continuous lines drawn so as to form the figures from one plane to the other. Mainly used in orthographic projections in which different views can be easily drawn with the help of these lines. Cutting plane line (Use H and HB pencil) It is a thin chain line, thick at ends and changes its direction. It is used to show the cutting plane as a trace in the given view. Break lines (Use H pencil) Medium Dark It is a wavy continuous line drawn by free hand or a straight continuous line with Zig-zags to represent any breaks. Hatching lines (Use H pencil) Medium Dark The minimum space between two parallel lines in sectioning should be 2.5 to 3 mm and the inclined angle of the hatching lines should be 30 to 45. Generally it is taken as 45.

20 1.14 Engineering Graphics - Tips for Good Quality Drawing 1. Sharpen the tip of the pencil from time to time. 2. Avoid frequent use of eraser. 3. Complete a line, circle or arc in one stroke only. 4. Use a bow compass to draw smaller circles or arcs. 5. Maintain constant hand pressure while drawing a particular line, circle or arc. 6. Check frequently the zero (0) setting of drafter scale. 7. Don t use a drafter to draw measured inclinations. Use a protractor for this purpose. 8. Protect your drawing sheet by covering chart, roll it properly and place a rubber-band over it. DIMENSIONING A detailed drawing, in addition to giving the shape and size of an object should furnish the reader with information like the distance between the surfaces, type of material, type of finish, position of holes, number required and so on. The expression of this relevant information on a drawing by the use of lines, symbols, numerals and notes is called dimensioning. Elements of dimensioning The elements of dimensioning consists of dimension line, projection line, leader line, the origin indication, symbols, figures and notes, etc. Dimension line Dimension line is a continuous thin line terminated at each end by an arrow head. It is drawn parallel to the edge or surface whose measurement is to be shown. It should be placed out side the object line and should be approximately 12 mm gap between the object and the dimension line. The next dimension line to dimension line must be a gap of minimum 10 mm. Projection line (or) Extension line It is a thin continuous line extending from the out line of the object to indicate the measurement given by the dimension line. The arrow heads at both ends of the dimension line should touch the projection lines. This line should extend about 3 mm beyond the dimension line. This projection line should not cross the dimension line.

21 Introduction 1.15 Arrow heads Dimension lines are terminated by arrow heads. It is recommended that the barbs of the arrow head form an inclined angle of 15 or more to produce an arrow head of length at least three times the width as shown in fig. Arrow heads should be drawn with in the limits of the dimensioned feature. When enough space is not available, they should be placed outside also. The arrow heads may be open, closed or closed and filled in as shown in fig. Leader line (IS: ) Leader lines are continuous thin lines drawn from notes and figures to refer a feature (dimension, object, outlines etc.). They may be drawn at 30 or 45 to the horizontal.

22 1.16 Engineering Graphics - Unit of dimensioning As far as possible, dimensions should be expressed in one unit only. The recommended unit is millimeter. It is not necessary to express the dimensions (mm) at all the places in the figure. Instead, All dimensions are in mm is written at a predominant place on the drawing sheet. Systems of Dimensioning IS has recommended the following two systems of placing the dimensions on a drawing. (i) Aligned system (ii) Unidirectional system (i) Aligned system In this system, all the dimensional values are placed above the dimension lines and written parallel to them without breaking the dimension lines. Therefore, they can be read either from bottom or any one of the other sides of the drawing as shown in figures. Angular dimensions are placed as shown in fig. (ii) Unidirectional system In this system, the dimensional values are placed at the centre of the dimension line as shown in fig, so as to read from the bottom of drawing sheet. Here the dimension lines may be interrupted preferably near the middle to insert the dimensions. This method is preferable than the first one. Angular dimensions are placed as shown in fig. If the angle is very small say 15, it can be marked out side also which is shown in fig.

23 Introduction 1.17 Dimensioning of diameters and circles The dimensioning of diameters and circles are placed as shown in fig. using the symbol. PRINCIPLES OF DIMENSIONING The general principles of dimensioning should be followed by the students in engineering drawing practice are 1. Arrow head should touch the extension line but it never cross it. 2. Dimension lines are thin lines which are drawn by using H pencil. 3. Dimensions should be placed outside the object, if possible. 4. Extension line should not cross the dimension lines. 5. Extension lines should extend slightly beyond the dimension line i.e., 3 mm beyond the dimension line. 6. The dimension line should be at a distance of about 12 mm away from the object lines. The next successive dimension lines should be with a gap of 10 mm from the first dimension line.

24 1.18 Engineering Graphics Dimensions should be marked only in the visible outlines not from the hidden lines. 8. Unnecessary dimensions should be avoided. Dimensions placed in one view should not be repeated in the other view. Every dimension should be placed once only. 9. For all the views, overall dimensions like length, breadth and height should be marked. 10. Centre lines should not be used as dimension lines except when centre line passes through the centre of the hole. 11. Always place a smaller dimension first and then larger dimensions, so that the extension line will not cross the dimension line. 12. If enough space is not there, arrow heads can be placed outside the projection lines. i.e. for smaller dimensions (which are less than 10 mm) LETTERING In Engineering Drawing, it is necessary to represent the sizes of the object with some written details, to convey the technical information such as name of the company, part details, information regarding the part, manufacturing process etc., Representing the particulars and sizes of the object or component on an engineering drawing is known as Lettering and Numbering. The important features of the lettering are, 1. LEGIBILITY 2. UNIFORMITY 3. NEATNESS 4. SUITABLE FOR AMMONIA PRINTING, XEROXING, MICRO FILMING etc., Lettering can be done 1. By free hand 2. By using stencils. Proficiency in free hand lettering can be achieved by selecting proper size of the letter, use of the proportions and regular practice. Single stroke lettering is adopted by the Bureau of Indian Standards, IS 9609 for engineering drawings. In single stroke lettering the thickness is uniform in the letters and Numerals.

25 Introduction 1.19 Required parameters for lettering: (a) height of the capital letters and lower case letters (b) line thickness (c) spacing between letters (d) spacing between the words The lettering and numbering may be vertical or inclined. The inclination for an inclined lettering and inclined numbering is 75 to the horizontal or 15 to the vertical. In engineering drawing all the letters must be in uppercase and lowercase letters are used for abbreviations. Same line thickness is used for both uppercase and lowercase letters to maintain the uniformity. LETTERING NOMENCLATURE h height of the letter. b line thickness. c spacing between letters. d spacing between words. Types of lettering: There are two types of lettering recommended. 1. Lettering type - A 2. Lettering type - B In both the types, according to the given height of the capital letters h, width of the letter, thickness of line, spacing between letters, spacing between words are expressed in terms of the height of the capital letter. In lettering A - type, the height of the capital letter is divided into 12 equal parts. In lettering B - type, the height of the capital letter is divided into 10 equal parts.

26 1.20 Engineering Graphics - Specifications of lettering - type A: Let h capital letter height given. For lower case letters the height 5 7 h Thickness of line 1 14 h Spacing between letters 1 7 h Spacing between words 3 7 h Specifications of Lettering - type B: Let h height of the uppercase letter, given. For lowercase letters the height 7 10 h Thickness of lines 1 10 h Spacing between letters 1 5 h Spacing between words 3 5 h Recommended height of letters and Numerals: The recommended height of the letters for use in engineering drawing are 2.5, 3.5, 7, 10, 14, 20 mm. Specifications of letters and Numerals: (All dimensions are in mm) 1. Name of the Industry or Company: h 10, 14, Drawing Numbers, Letters representing section planes. h 10, Title of the drawing h 7, Sub - Titles h 5, 7 5. Dimensioning, Notes, Parts list, Material list. h 3, 5, 7 Lettering Practice: In lettering practice, to represent the standard recommended shapes for the letters and numerals, it is necessary to maintain proportionate width to height for each of the letters and numerals. Lettering - A type: Vertical Letters and Numerals: Let each unit or box is 2 mm 2 mm Take height 6 units or box

27 Introduction 1.21 The width of letters as in the tabular coloumn: Letter A and M W Rest of the letters: B to L N to V and X TO Z Width 5 units 7 units 4 units The ratio of the height to width varies but in most of the cases it is taken as 7:5 or 6:5. The lettering is usually done in uppercase letters. The lower case letters are usually used in architectural drawings. I.S.O. STANDARDS AND BUREAU OF INDIAN STANDARDS (B.I.S) The growing international Engineering and Technological development, the introduction of foreign technologies and the technical collaboration between different countries make the inter - nationalization of engineering drawing standards into essential. International Standards Organization (I. S. O) Geneva, has formulated such international standards for Engineering Drawing. According to this, our country has modified the Indian Standards IS to IS: Indian Standards Institution (I.S.I) is recently renamed as Bureau of Indian Standards (B.I.S) These standards are used for the following topics in the field of Engineering Drawing. 1. Drawing sheets: (Sizes, layout etc.) IS: , 2. Lines: (General principles of presentation of Technical Drawings) IS: Lettering for Technical Drawings: IS: Methods of dimensioning: IS:

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29 Introduction 1.23

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31 Introduction 1.25