Student's Book. Engineering drawing N2

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2 FET FIRST NATED Series Engineering drawing N2 Student's Book A. de Bruin

3 FET FIRST Engineering Drawing N1 Student s Book A. de Bruin, 2013 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, photocopying, recording, or otherwise, without the prior written permission of the copyright holder or in accordance with the provisions of the Copyright Act, 1978 [as amended]. Any person who does any unauthorised act in relation to this publication may be liable for criminal prosecution and civil claims for damages. First published 2013 by Troupant Publishers [Pty] Ltd Suite 10, Private Bag X12 Cresta 2118 Author: A. de Bruin Copy editing by D. Hawkins Proofreading by B.M. Davies Cover design by R. de Wet Typesetting by The Purple Turtle Publishing Distributed by Macmillan South Africa [Pty] Ltd ISBN: ; eisbn: It is illegal to photocopy any page of this book without written permission from the publishers. While every effort has been made to ensure the information published in this work is accurate, the authors, editors, publishers and printers take no responsibility for any loss or damage suffered by any person as a result of reliance upon the information contained therein. The publishers respectfully advise readers to obtain professional advice concerning the content. To order any of these books contact Macmillan Customer Services at: Tel: (011) Fax: (011) customerservices@macmillan.co.za

4 Contents Syllabus grid... vi Module 1 Drawing terminology, abbreviations and Computer Aided Drafting (CAD) Abbreviations and terms used in Engineering Drawing Basic computers Plotters and pointers used in industry Storage devices Backup systems...5 Exercise...5 Module 2 Fastening devices and welding Introduction The construction of hexagonal nuts, bolts, studs and drilled and tapped holes Bolt heads Machine screw heads Locking devices Welded joints Types of welding symbols and representation Supplementary welding symbols...13 Exercise...13 Module 3 Screw threads Introduction Construction of external and internal single start V-screw threads Construction of external and internal single start square threads Screw thread terminology...19 Exercise...19 Module 4 Machining symbols Introduction The basic machining symbol Identification and correct use of the machining symbol Roughness values and grade numbers Application of machining symbols including roughness values Production method, treatment and coating The placing of machining symbols...23 Exercise...23 Module 5 First angle orthographic projections Introduction First angle primary orthographic views Projection symbol...26 Exercise...27 iii

5 Module 6 Isometric drawing Introduction Construction of an isometric drawing Angles in isometric projection Isometric projection of circles...39 Exercise...41 Module 7 Third angle orthographic projection Introduction Primary orthographic views Projection symbol...46 Exercises...46 Module 8 Interpenetrations Introduction Tee-ends Forked ends...54 Exercise...55 iv

6 Syllabus Grid: Engineering Drawing N2 Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 1: GENERAL ENGINEERING DRAWING TERMS (WV 5) Identify and correctly use the abbreviation for the following terms used in Engineering Drawing: Give the basic function of the following hardware and software as used in Computer Aided Draughting (CAD): Centres Centre-line Cylinder and cylindrical Degree (of angle) Diameter Drawing Hexagon Internal diameter Outside diameter Material Maximum Metre Millimetre Radius. DOS (disk operating system) CAD (computer aided draughting) Keyboard Mouse Tablet Scanner CPU (central processing unit) RAM (random access memory) ROM (read only memory) Plotter/printer. Monitor Hard drive/fixed disk CD ROM (compact disk, read only memory) Floppy disk Stiffy disk Directory Files Sub-directory DIDACTICAL GUIDELINES Effective use can be made of multi-choice type of questions for testing and evaluation. Develop the students understanding of computers and CAD by demonstrating the actual hardware and software wherever possible. Effective use can be made of available wall charts vi

7 Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 2: FASTENING DEVICES AND WELDING (WV 15) Draw and construct views of hexagonal head bolts, nuts, studs, drilled holes and tapped holes by using the conventional method Draw free-hand and identify the specific application of the following: Draw free-hand and identify the following types of welded joints: Apply welding symbols to specify the following three welds: Interpret and indicate the following supplementary symbols: Bolt heads square-head bolt; tee-head bolt; cheese-head bolt; and hook-head bolt Machine screw heads round head; cheese head; fillister head; socket head; countersunk head; and instrument head Locking Devices spring washer; Simmonds nut; slotted nut; castle nut; tab washer; lock-nut; and parallel, taper and gib-head keys PVC conduit fittings and fasteners male and female adapter; 20 mm connection box; and 20 mm inspection coupling Metal conduit fittings and fasteners 20 mm lock-nut; 20 rnm female bush/bush nut; 20 mm end box; and distribution board entry off-set butt, lap, tee and corner. square butt weld; single V-butt weld; and fillet weld. weld all round; weld on site; and weld all round on site. Note: All welding symbols must comply with the Code of Practice for Welding, SABS Part 2. vii

8 DIDACTICAL GUIDELINES The approximate proportions given below should be used for the construction of the following: Hexagonal bolt/nut = 1 5 D (across flats) Height of bolt head = 0,7 D Height of nut 0,8 D Thread 0 1 D Thread before nut 0 3 D Thread after nut 0 3 D A nut/bolt template may be used. When drawing fastening devices in position, care should be taken with regard to the line types as well as the relevant angle of drilled and tapped holes and stud chamfers. The approximate proportions given below should be used for the construction of the following: Width of Key = 0,25 D Length of Key = 1,5 D Taper of Key = 1: 100 Thickness of Key = 0,167 D Where D is the nominal diameter of the shaft. When inserting welding symbols on a drawing it is necessary to indicate on which side of the reference line the welding must be done. Welding symbols should be approximately 5 mm to 8 mm in size and drawn with a type A-line. The reference line and indicating line should be drawn with a type B-line. Each lecturer presenting this module should consult the Code of Practice for Welding, SABS Part 2. Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 3: SCREW THREADS (WV 10) Draw the following representations of metric screw threads: Detailed representation of internal/external singlestart left and righthand V-screw threads Detailed representation of internali external singlestart left and righthand square threads. 3.2 Explain the relevant terminology applicable to screw threads. DIDACTICAL GUIDELINES The difference between left and righthand screw threads should be clearly demonstrated by means of models. The construction of the true helical forms is not required. The difference between the detailed and conventional representation of screw threads should be clearly explained. Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 4: MACHINE SYMBOLS (WV 5) Draw the basic machining symbol 4.2 Identify and use the correct machining symbol to indicate that material must be removed by machining machining is not permitted. 4.3 Read and correctly apply surface texture symbols from a table giving roughness values and grade numbers. 4.4 Specify surface textures by using the appropriate machining symbol with the required roughness value. 4.5 Specify a production method, treatment, or coating for producing a surface texture including the following: specifying the sampling length indicating the direction of lay indicating machining allowance avoiding unnecessary repetition of a symbol. 4.6 Use the correct method for indicating the symbols as well as a suitable size and proportion for the symbols. viii

9 DIDACTICAL GUIDELINES Refer to the latest copy of SABF 0111, Code of Practice for Engineering Drawing and the additional Code of Practice for Engineering drawing at technical colleges. Extracts from tables for machining symbols will be given in the examination paper. Students are not required to purchase their own tables. Emphasize that the machining symbol must be placed so that it: may be read from the bottom or may be read from the righthand side of the side of the drawing sheet. Use models with appropriate surface textures to demonstrate the significance of the symbols to the students. Arrange a visit to a machine shop, to show the students which machines are used to obtain the various types of surface textures. Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 5: FIRST ANGLE ORTHOGRAPHIC PROJECTION (WV 20) Draw the primary orthographic views to scale including full, half or partial sectional views of casting or multi-part objects of the following: Knuckle joints Cottered joints Flanged couplings Simple bearings Brackets Pulleys Connecting rods Internal combustion engine pistons Electric motor fan and housing Distribution board and mounting chassis. Isolating links Safety valves Knife switches Draw the orthographic views to scales of 1:1, 1:2, 1:5 1:10 and 2: Draw the recognised symbol of projection for first angle orthographic projection. The following must be considered: Assemblies of multi-part objects must have a maximum of five components excluding fasteners. The fastening devices required are those listed in module 2. Drilled and tapped holes, bolts, nuts and studs are to be indicated in conventional representation. Items that are not sectioned in their length, i.e. fastening devices, pins, shafts, spokes, ribs and webs. Dimensioning and printing of the title and scale may be required. DIDACTICAL GUIDELINES Refer to the latest copy of the SABS 0111, Code of Practice for Engineering Drawing and the additional Code of Practice for engineering drawing at technical colleges. Use various models and wall charts to assist with the visualization and perception and give more meaning of the contents to the students. Cutting planes lines are short chain lines suitably thickened at the ends (refer to the SABS 0111, Code of Practice for Engineering Drawing). Note should be taken that the angle of sectioning is normally 45 degrees. Section lines must be equally spaced, drawn with the Type E line. Scribed set squares should be used to ensure equal spacing of the section lines. The scribed side must be placed flush to the drawing sheet to avoid the error of parallax. Hi den detail on views that are in section is not shown unless it is absolutely necessary. ix

10 Page in SB Learning content Learning objectives On completion of this module the student must be able to draw an isometric drawing of a single item of which at least two views are given in first angle orthographic projection. The following must be considered: MODULE 6: ISOMRRIC DRAWING (WV 15) 15 The isometric four centre method should be used for the construction/drawing of isometric circles and arcs. Hidden detail may be required. Centre lines should be inserted where appropriate. Dimensions are not required. The isometric scale is not required. DIDACTICAL GUIDELINES Models, wall charts as well as clay or modelling wax can be beneficially used to assist the student to visualize three dimensional objects and to develop the necessary insight. Free-hand isometric drawing, using isometric grids should be used to develop skills in this module. Hidden detail in isometric drawing is generally reserved for holes or channels, to indicate whether the detail has a dead-end or passes right through the object. The more complex the drawing the more confusion is created with the insertion of all hidden detail. The isometric scale is not used in isometric drawing Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 7: THIRD ANGLE ORTHOGRAPHIC PROJECTION (WV 20) Draw the primary orthographic views to scale including a full, half or partial sectional views of castings or multipart objects, from the following starting situations: An isometric drawing is given of which two or three views must be drawn according to third angle orthographic projection. Two views (outside or sectional) of a single item or multi-part objects are given in third angle orthographic projection from which a third view must be drawn with the aid of projection Draw the orthographic views to scales of 1:1, 1:2, 1:5, 1:10 and 2: Draw the recognised symbol of projection for third angle orthographic projection. The following must be considered: Assemblies of multi-part objects must have a maximum of five components excluding fasteners. Drilled and tapped holes, bolts, nuts and studs are to be indicated in conventional representation. The fastening devices required are those listed in module 2. Items that are not sectioned in their length, i.e. fastening devices, pins, shafts, spokes, ribs and webs. Dimensioning and printing of the title and scale may be required. DIDACTICAL GUIDELINES Refer to the latest copy of the Code of Practice for Engineering Drawing - SABS 0111 and the additional Code of Practice for Engineering drawing at technical colleges. Use various models and wall charts to assist with visualization and perception. Note should be taken of the angle and the equal spacing of section lines (45 degrees is accepted as the norm). Hidden detail is not shown on views that are in section unless it is absolutely necessary. The principles of third angle orthographic projection should be demonstrated by means of the principal reference planes (horizontal and vertical) with special reference to the viewing position, placing of objects, rabatting (opening out) of reference planes and the placement of orthographic representations. x

11 Page in SB Learning content Learning objectives On completion of this module the student must be able to MODULE 8: INTERPENETRATIONS (WV 10) Draw a given view and insert the curve of interpenetration of the following pipes or prisms: Draw given views and insert curves of interpenetration for the following: Triangular, Square, rectangular, hexagonal, octagonal, circular T-ends, fork-ends and rod-ends The following must be considered: The axes of the pipes and prisms must intersect at right angles and both axes must be parallel to one of the principal planes. The axes must lie in the same parallel plane (not offset). For the construction of the curve of interpenetration in T-ends fork-ends and rod-ends a minimum of five points per symmetrical half is required, i.e a starting point, a turning point and three points in between. Numbering of points is required in the construction. Dimensions are not required. DIDACTICAL GUIDELINES Models and wall charts should be used to assist the students to develop the necessary insight and spatial perception. xi

12 Module 1: DRAWING TERMINOLOGY, ABBREVIATIONS AND COMPUTER AIDED DRAUGHTING (CAD) Learning objectives: On completion of this module you will be able to: identify and apply the abbreviation for some terms used in engineering drawing name types of plotters and printers used in industry and give one advantage and one disadvantage of each list and describe different types of storage devices used in microcomputers explain why backup systems are necessary. 1.1 Abbreviations and terms used in engineering drawing Across flats A/F Across corners A/C Assembly ASSY Chamfered CHAM 1

13 Countersunk CSK Countersunk head CSK HD Counter-bore C BORE Hexagon head HEX HD Pitch circle diameter PCD 2

14 1.2 Basic computers Tablet Scanner Keyboard Mouse INPUT Input devices allows you to communicate with your computer PROCESSING THE Central Processing Unit (CPU) performs calculations, processes instructions and manages information. OPERATING SYSTEM Like a conductor, the operating system (Win 95) allows the hardware and software to work together. OUTPUT Output devices allows your computer to communicate with you STORAGE Like a filing cabinet, a computer stores information Hard disk Memory stick Monitor SOFTWARE Software allows you to write books, make drawings, do accounts etc. Hard drive Printer External hard drive CD-ROM 3

15 1.3. Plotters and printers used in industry Pen plotters Advantages: Excellent quality possible. Colour plotting possible. Disadvantages: Very expensive. Replacement pens rather expensive too Inkjet plotters Advantages: Print quality is very high, and quality colour printing is possible. Printer operates relatively quietly. Disadvantages: Printers are rather expensive and ink usage can be excessive. The ink needs an amount of drying-out time, so smudging is easy Thermal printers Advantages: Low noise levels. Disadvantages: Special paper must be used which reacts to heat, so normal paper cannot be used. Special coated paper is rather expensive Laser printers Advantages: Unsurpassed quality is possible. Quiet operation. Colour printing also possible. Disadvantages: Expensive. Ink cartridges relatively expensive. 4

16 1.4. Storage devices Removable storage devices Removable storage has been around almost as long as the computer itself. Early removable storage was based on magnetic tape like that used by an audio cassette. New removable storage devices can store gigabytes of data on a single disk. There are several reasons why removable storage is useful: Making back-up copies of important information Transporting data between two computers Storing software and information that you don t need to access constantly Copying information to give to someone else Securing information that you don t want anyone else to access Some types of removable media are designed to be read by removable readers and drives. Examples include: Optical discs (Blu-ray discs, DVDs, CDs) Memory cards (CompactFlash card, Secure Digital card, Memory Stick) Floppy disks / Zip disks Magnetic tapes Paper data storage (punched cards, punched tapes) Some removable media readers and drives are integrated into computers, others are themselves removable. Removable media may also refer to some removable storage devices, when they are used to transport or store data. Examples include: USB flash drives External hard disk drives Hard/fixed drives These disks are fixed to the computer and can essentially be described as fixed disks. The capacities of these drives, is constantly expanding Data can also be accessed much faster than with removable storage devices Backup systems Why are backup systems necessary? Hard/fixed disk Should problems occur with the hard disk drive, all data could be lost. It is thus of the utmost importance to make copies (backup) of work done on the computer on a regular basis. Exercise 1. Make freehand sketches to illustrate what is meant by the following: across flats, across corners, chamfered, countersunk, countersunk head, counter-bore, hexagon head, across flats and pitch circle diameter. 2. Give one advantage and one disadvantage of the following printing devices: pen plotters ink jet printers thermal printers laser printers. 3. Describe what is meant by removable storage devices. 4. Explain why backup systems are a necessity. 5

17 Module 1: 2: The FASTENING challenges DEVICES of entrepreneurship AND WELDING Overview Learning objectives: When On completion you have of completed this module this you Module, will be you able should to: be able to explain and demonstrate how to: Unit draw 1.1: and Distinguish construct views between of hexagonal the roles of head entrepreneurs bolts, nuts, studs, and intrapreneurs drilled holes and tapped Unit holes 1.2: by using Name the and conventional briefly describe method the qualities of the entrepreneur and apply to case studies of successful draw freehand entrepreneurs and identify the specific application of the following: Unit Locking 1.3: Name devices and describe personal resources; list Machine strengths screw and heads weaknesses; identify assistance to the spring business; washer and calculate net worth round head Unit Simmonds 1.4: Briefly nut discuss the economic importance of cheese-head the entrepreneur, with reference to the South African slotted situation nut fillister head Unit castle 1.5: Name nut and explain the advantages and opportunities socket headof entrepreneurship Unit tab 1.6: washer Name and explain the reasons why businesses countersunk fail; discuss head how entrepreneurs can overcome lock-nut these problems instrument head. Unit parallel, 1.7: Name taper and and describe gib-head the keys. reasons why businesses succeed Unit Bolt 1.8: heads Complete a self analysis, listing personal Metal strengths conduit and fittings weaknesses, and fasteners possible contacts and personal square-head investment bolt capabilities 20 mm lock-nut tee-head bolt 20 mm female bush/bush nut cheese-head bolt 20 mm end box hook-head bolt. distribution board entry offset. PVC conduit fittings and fasteners male and female adaptor 20 mm connection box 20 mm inspection coupling. draw freehand and identify the following types of weld joints: butt, lap, tee and corner. apply welding symbols to specify the following three welds: square butt weld single vee-butt weld fillet weld. interpret and indicate the following supplementary symbols: weld all round weld on site weld all round on site. Note All welding symbols must comply with the Code of Practice for Welding, SABS 044 Part Introduction Threaded fasteners are used for holding together parts which may require dismantling,locking devices are used when parts are subjected to vibration, etc., and there is a possibility of a part coming loose. Welding is used to create a permanent bond between two parts. 6