The TVET First NATED Series offers students and lecturers a wide range of courses, written by lecturers, examiners and subject experts. Troupant/Macmillan have developed brand new books that cover the curriculum and that address developments in the various fields by bringing subject matter up to date. The books include: Engineering Drawing N1 Engineering Drawing TVET FIRST NATED SERIES NATED Series N1 Engineering Drawing relevant and attractive illustrations activities examples N1 Student s Book engineering drawing N1-A4.indd 1 M Cameron Student s Book TVET FIRST NATED SERIES new word definitions. 2015/03/05 1:47 PM
N1 Engineering Drawing Student s Book M Cameron
Engineering Drawing N1 Student s Book M Cameron, 2012 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 in 2012 by Troupant Publishers [Pty] Ltd PO Box 4532 Northcliff 2115 Distributed by Macmillan South Africa [Pty] Ltd ISBN: 978-1-4308-0045-3 Web PDF ISBN: 978-1-4308-0224-2 It is illegal to photocopy any page of this book without written permission from the publisher. While every effort has been made to ensure the information published in this work is accurate, the authors, editors, publisher and printers take no responsibility for any loss or damage suffered by any person as a result of reliance upon the information contained herein. The publisher respectfully advises readers to obtain professional advice concerning the content. While every effort has been made to trace the copyright holders and obtain copyright permission from them, in some cases this has proved impossible due to logistic and time constraints. Any copyright holder who becomes aware of infringement on our side is invited to contact the publisher. Note: Any reference to Further Education and Training (FET) in this book should be taken to mean Technical and Vocational Education and Training (TVET). To order any of these books, contact Macmillan Customer Services at: Tel: (011) 731 3300 Fax: (011) 731 3535 E-mail: customerservices@macmillan.co.za
Contents Module 1: General engineering terms...1 Introduction... 1 Unit 1: Terms used in Engineering Drawing... 2 Unit 2: Basic computers, storage devises and terms associated with computer aided design (CAD)... 5 Module 2: Drawing instruments and drawing technique...12 Introduction to technical drawing...12 Unit 1: Instruments, equipment and their uses...12 Unit 2: Line types... 22 Unit 3: Freehand lettering and dimensioning... 23 Module 3: Freehand drawing...28 Introduction to freehand... 28 Unit 1: Draw freehand... 29 Module 4: Geometrical construction...35 Introduction... 35 Unit 1: Use geometrical constructions involving lines and circles... 35 Module 5: Reproduction drawing...49 Introduction to reproduction drawing...49 Unit 1: Geometrical plane figures...49 Unit 2: Single objects or castings drawn to scale... 52 Module 6: First-angle orthographic projection...57 Introduction to first-angle orthographic projection...57 Unit 1: First-angle orthographic projection...57 Module 7: Axonometrical drawing...81 Unit 1: Oblique drawings...81 Unit 2: Isometric drawings... 85 Module 8: Orthographic projection of prisms and pyramids...99 Introduction... 99 Unit 1: Creating an orthographic projection of prisms and pyramids...101 Module 9: Sectional drawing of single items...106 Introduction...106 Unit 1: Basics of sectioning...106 Module 10: Examination hints... 114 EngDrawN1.indd 3 2013/10/29 03:02:57 PM
Module 1: General engineering terms Learning outcomes On completion of this module you should be able to: Unit 1: Identify and correctly use the abbreviations for the following terms used in Engineering Drawing: Centres Cylinder and cylindrical Diameter Outside diameter Hexagon Maximum Millimetre Centre line Degree (of angle) Internal diameter Drawing Material Metre Radius Unit 2: Give the basic function of the following hardware and software as used in Computer Aided Design (CAD): DOS (Disk operating system) Keyboard Tablet CPU (central processing unit) ROM (read only memory) Hard drive/fixed disk Floppy disk Stiffy disk Directory Sub-directory Files CAD (computer aided draughting) Mouse Scanner RAM (random access memory) Monitor CD ROM (compact disk, read only memory) Plotter/printer The weight value for this module should be allocated as 5% and the approximate time allocated during the course is 3 hours 45 minutes. Introduction What is engineering drawing? For one thing, it is an effective means of communicating technical ideas and problem solutions. Look at what happens in engineering design. The process starts with the ability to visualize, seeing the problem and the possible solutions. Then, sketches are made to record initial ideas. Next, geometrical models are created from those sketches and are used for analysis. Finally, detail drawings or three-dimensional models are made to record the precise data needed for the production process. Visualizing, sketching, modelling, and detailing are how engineers and technologists communicate as they design new products and structures for our technological world. Actually, communication using engineering drawings and models is a language, a clear, precise language with definite rules that must be mastered if you are to be successful in engineering design. Once you know the language, it will influence the way you think, the way you approach problems. Universally accepted, conventional and standardized methods of communication through engineering drawings are used. This is so that any designers here, and in other countries, will be able to read and interpret each other s drawings in exactly the same way. Components (machine parts) shown in a drawing can therefore be made by suitably skilled craftsmen of any nationality, provided they can read an engineering drawing. If the drawings are correctly drawn and annotated (described) by means of notes, dimensions, etc., the finished product will be exactly as visualized by the designer. Any misunderstandings when describing shapes and size by using only words and no drawings are thus avoided. 1 EngDrawN1.indd 1 2013/10/29 03:02:58 PM
Unit 1: Terms used in engineering drawing Centres Abbreviation: CRS Centre line Abbreviation: CL Cylinder and cylindrical Abbreviation: CYL 2 EngDrawN1.indd 2 2013/10/29 03:02:58 PM
Hexagon Abbreviation: HEX A hexagon is a polygon of six sides of the same length and six internal angles all of 120 DRG (120 ). Activity Give the abbreviations for the following: centre line, internal diameter, centres, material, drawing and radius. Unit 2: Basic computers, storage devices and terms associated with computer aided draughting (cad) 5 EngDrawN1.indd 5 2013/10/29 03:02:58 PM
Module 10: examination hints Candidate s information box The candidate s information, including the examination number, must appear in the information box. All the information must be filled in in pencil. THE COLLEGE NAME Grade Subject Centre No Date Exam. EXAMINATION NUMBER start time Your examination number is normally your Identity Document number. Border A 15 mm border (unless otherwise stated by the examiner) must be drawn on both sides of the sheet. Balanced layout Before you start the examination, read all the questions carefully and be sure you understand what is required. Only one drawing sheet is issued to candidates. It is very important, therefore, that candidates plan the layout of their work before commencing. Make sure that all the drawings will fit on the sheet. It is not required that Question 1 be on the same side of the drawing sheet as Question 2. The question numbers must be clearly indicated. 114 EngDrawN1.indd 114 2013/10/29 03:03:14 PM
Special sectioning conventions Ribs, webs, spokes, lugs, gear teeth, and other thin features are not section-lined when the cutting plane passes parallel to the feature. A rib or web is a thin flat part that acts as a support. When you add section lines to these features it gives a false impression that the part is thicker than it really is. The figure below shows a cutting plane that passes parallel to and through a web (section B - B). The figure marked (A) shows an incorrect representation of the section view, with the web having section lines. This view gives the false impression that the web has substantial thickness. The figure marked (B) shows the view drawn using conventional practice, leaving the web unsectioned, which is the correct way. If the cutting plane passes perpendicular or crosswise to the feature (cutting plane A -A), section lines are added as shown in the figure marked (C). Notes Section lines are drawn thin (0,35 mm), black, uniform and uniformly spaced. Section lines are drawn at 45 to the horizontal when possible. Section lines are not drawn parallel or perpendicular to the visible outline of the sectioned surface. Section lines do not extend beyond or stop short of the outline of the sectioned surface. Very thin parts are not shown with section lines. 109 EngDrawN1.indd 109 2013/10/29 03:03:13 PM
unit 1: Creating an orthographic projection of prisms and pyramids Example 1 The figure shows a front view and an auxiliary view of a rectangular square prism inclined at 45. Copy the given views and project a top view as seen in the direction of arrow Y and a left view as seen in the direction of arrow X. Solution 1 Step 1: Draw the auxiliary view as per the given measurements. Step 2: Project the front view from the auxiliary view. Step 3: Draw the lines X-X and Y-Y. Step 4: At the intersection of X-X and Y-Y draw a line OZ at 45. Step 5: From the front view, the left view and the top view are projected as shown by the arrows. It is clear that measurements 4, 3, 5 and 8 on the auxiliary view are equal to 1, 2, 3 and 4 on the top view and the left view. Alternative method of creating an orthographic projection of prisms and pyramids Solution 1 An alternative, and maybe an easier, method is shown below: Step 1: Draw the auxiliary view to the correct dimensions and scale. Step 2: Project the front view from the auxiliary view. Step 3: In between the auxiliary view and the front view draw line ZZ perpendicular to the front view angle. Draw the line anywhere in between. Step 4: From the front view, the left view and the top view, lines are projected across and downwards. Step 5: Measure the distance between line ZZ and point 2 on the auxiliary view with your dividers. Step 6: Transfer this measurement to line YY and line XX. In other words, draw construction lines parallel to XX and YY at the distance of the dividers. Step 7: Repeat with points 4, 5 and 8 on the auxiliary view. Step 8: The lines are then joined to obtain the full diagram. 101 EngDrawN1.indd 101 2013/10/29 03:03:10 PM