Principles Of Technical Drawing Pdf

Figures - uploaded by Segun R Bello

Author content

All figure content in this area was uploaded by Segun R Bello

Content may be subject to copyright.

Discover the world's research

20+ million members
135+ million publications
700k+ research projects

Join for free

ii | P a g e

Segun R. Bello

[MNSE, R. Engr. COREN]

Createspace.com

iii | P a g e

Technical Drawing

iv | P a g e

Presentation & Practice

Federal College of Agriculture Ishiagu, 480001 Nigeria

segemi2002@gmail.com; bellraph95@yahoo.com

http://www.dominionpublishingstores.yolasite.com

http://www.segzybrap.web.com

+234 8068576763, +234 8062432694

No part of this book may be reproduced, stored in a retrieval system or transmitted, in

any form or by any means, electronics, mechanical, photocopying, recording or

otherwise, without the prior written permission of the copyright holder.

Dominion

Publishing Services

ISBN-13: 978-1481250122

10: 1481250124

First published in December 2012

Printed by Createspace US

Createspace

7290 Investment Drive

Suite B North Charleston,

SC 29418 USA

www.createspace.com

v | P a g e

Dedication

To the glory of God Almighty

vi | P a g e

Acknowledgements

Glory be to God Almighty, the author of life and the giver of knowledge. I

acknowledged the several authors and researchers whose wealth of experiences

documented and made available in book and journal prints forms, as well as

numerous materials available of the web.

Many thanks to all students, past and present, that had passed through my tutelage as

instructor and teacher for their contributions, criticisms and feed-backs on the series of

classroom lectures and practical experiences which are documented in this book.

Special thanks go to my wife, who had always back-up the realization of God's plan

for me. She is a virtuous woman in class of her own. I am grateful for her

understanding and tolerance in taking full responsibility of running our home during

the scripting and review of this works.

I am grateful to my children, Ayomikun, Pelumi, Damilola and Adeola, who have

been so wonderful and cooperative during this period. I am encouraged and

strengthened by their prayers, my God shall surely reward them. Amen

vii | P a g e

Content

Dedication ............................................................................................................................ v

Acknowledgements ............................................................................................................ vi

Preface................................................................................................................................ xi

SECTION 1 Drawing Presentation ................................................ xiii

Chapter 1 Introduction to Technical Drawing .................................................. 15

1.1 Introduction .......................................................................................................... 15

1.2 Introduction .......................................................................................................... 15

1.3 Drawing language and standards ...................................................................... 16

1.4 Aim of drawing ..................................................................................................... 17

1.5 Types of drawing and views ............................................................................... 17

1.6 Engineering drawing requirements .................................................................... 18

1.7 Professional application of technical drawing ................................................... 19

1.8 Technical drawing and agricultural development .............................................. 19

1.9 Steps to planning drawing .................................................................................. 20

Exercise ............................................................................................................................. 20

Chapter 2 Drafting and Drawing Presentation .................................................. 21

2.1 Introduction to drafting ........................................................................................ 21

2.2 Drafting tools ........................................................................................................ 21

2.3 Importance of drafting ......................................................................................... 22

2.4 Drafting practices................................................................................................. 23

2.5 Drafting aids/instruments .................................................................................... 24

2.6 Using the instruments ......................................................................................... 36

2.7 Drawing reproduction .......................................................................................... 45

2.8 Scales in drawing ................................................................................................ 46

2.9 Components of drawing ...................................................................................... 53

Exercise ............................................................................................................................. 54

Chapter 3 Lettering Principles and Practice ..................................................... 58

3.1 Introduction .......................................................................................................... 58

3.2 Importance of lettering ........................................................................................ 58

3.3 Types of lettering ................................................................................................. 58

3.4 Style of lettering ................................................................................................... 59

3.5 Lettering fonts in drawing .................................................................................... 59

3.6 Lines in lettering .................................................................................................. 59

3.7 Lettering practice ................................................................................................. 60

viii | P a g e

3.8 Drawing lettering lines ......................................................................................... 61

Exercise ............................................................................................................................. 62

Chapter 4 Principles of Dimensioning ................................................................ 64

4.1 Importance of dimensioning ................................................................................ 64

4.2 Guidelines for dimensioning ................................................................................ 64

4.3 Types of dimensions............................................................................................ 64

4.4 Components of dimension .................................................................................. 65

4.5 Dimension placement .......................................................................................... 65

4.6 Rules of dimension .............................................................................................. 68

4.7 Types of dimensioning ........................................................................................ 70

4.8 Dimensioning best practices ............................................................................... 79

Exercise ............................................................................................................................. 80

SECTION 2 Drawing Geometry & Projections ............................................. 83

Introduction ......................................................................................................................... 85

Chapter 5 Geometrical Figures: Properties and Construction ................... 87

5.1 Introduction .......................................................................................................... 87

5.2 Point ...................................................................................................................... 87

5.3 Lines, properties, application and construction ................................................. 88

5.3.1 Line styles ............................................................................................................ 89

5.3.2 Forms of lines ...................................................................................................... 90

5.3.3 Types of lines ....................................................................................................... 90

5.3.4 Line applications .................................................................................................. 92

5.3.5 Line drawing ......................................................................................................... 93

5.3.6 Line construction .................................................................................................. 94

5.3.7 Loci: Properties and construction ..................................................................... 101

5.4 Plane and solid loci ............................................................................................ 104

5.5 Plane figures ...................................................................................................... 105

5.5.1 Angles and their properties ............................................................................... 106

5.5.2 Triangles, their properties and construction .................................................... 108

5.6 Quadrilaterals, their properties and construction ............................................ 114

5.7 Polygon, their properties and construction ...................................................... 117

5.8 Circles, their properties and construction ........................................................ 124

5.8.1 Circle geometry .................................................................................................. 127

5.8.2 Tangency and normalcy construction .............................................................. 134

Exercise ........................................................................................................................... 138

Chapter 6 Projections in Engineering Drawings ............................................. 143

6.1 Drawing presentation ........................................................................................ 143

ix | P a g e

6.2 Features of projection ....................................................................................... 145

6.3 Projection of points ............................................................................................ 147

6.4 Projection of lines .............................................................................................. 147

Chapter 7 Descriptive Geometry ............................................................... 154

7.1 Introduction ........................................................................................................ 154

7.2 Orthographic projection ..................................................................................... 154

7.3 Multiview projection ........................................................................................... 156

7.4 Principles of first angle orthographic projection .............................................. 164

7.5 Principles of third angle orthographic projection ............................................. 169

7.6 Symbols for orthographic projection ................................................................ 172

7.7 Comparing 1st and 3rd angle projection ............................................................ 173

6.5 Auxiliary projection ............................................................................................ 173

Exercise ........................................................................................................................... 181

Chapter 8 Pictorial Drawing and Construction .............................................. 183

8.1 Introduction ........................................................................................................ 183

8.2 Projection of pictorial drawing........................................................................... 183

8.3 Isometric drawing .............................................................................................. 184

8.4 Oblique drawing ................................................................................................. 189

8.5 Axonometric drawing ......................................................................................... 191

8.6 Perspective drawing .......................................................................................... 192

8.7 Diametric drawing .............................................................................................. 197

8.8 Model building drawings ................................................................................... 197

8.9 Assembly drawings ........................................................................................... 199

8.10 Sketch drawings ................................................................................................ 201

8.11 Comparing projections ...................................................................................... 208

Exercise ........................................................................................................................... 209

SECTION 3 Conic Sections & Surface Development ............................. 212

Introduction ...................................................................................................................... 214

Chapter 9 Conic Sections and Construction .............................................. 215

9.1 Introduction ........................................................................................................ 215

9.2 Construction of conic sections .......................................................................... 218

9.2.1 Ellipse and its construction ............................................................................... 218

9.2.2 Hyperbola and its construction ......................................................................... 232

9.2.3 Parabola and its construction ........................................................................... 236

Exercise ........................................................................................................................... 242

Chapter 10 Solid Sections and Development .......................................... 244

10.1 Introduction ........................................................................................................ 244

x | P a g e

10.2 Types of sections ............................................................................................... 247

10.3 Hatching ............................................................................................................. 251

10.4 Sections of solid ................................................................................................. 254

10.5 Surface development ........................................................................................ 262

10.5.1 Full surface development of geometrical solids .......................................... 263

10.5.2 Development of lower surfaces of geometrical solids ................................ 265

10.5.3 Interpenetration of surfaces .......................................................................... 271

Exercise ........................................................................................................................... 277

References....................................................................................................................... 279

Notes ................................................................................................................................ 280

xi | P a g e

Preface

Engineering/technical drawing is a pre-requisite course for all who wish to pursue a

career in engineering profession especially in design and construction program.

Emphasis is placed on media drafting, lettering, and alphabet of lines, geometric

construction, sketching, and multiview drawings. Students learn traditional drafting

techniques through the study of geometric construction at which time they are

introduced to computer aided drafting and design.

This book is therefore designed to help students acquire requisite knowledge and

practical skills in engineering/technical drawing practices. The contents were

designed to prepare students for technical, diploma and degree examinations in

engineering, engineering technology and technical vocations in other professions in

the monotechnics, polytechnics and universities.

Therefore, when armed with this book, students should be able to;

Understand the principles and techniques of drawing, presentation and projections

Understand drawings and its applications to geometry; plane or solid

Understand the principles and application of free hand sketching

Understand development of surfaces and conic-sections

At the end of each chapter are lists of practical exercises that will help students perfect

their skill and proficiency in technical works.

Segun R. Bello

480001, Nigeria

xiii | P a g e

SECTION 1

Drawing Presentation

Page | 15

Chapter 1

Introduction to Technical Drawing

1.1 Introduction

One of the best ways to communicate one's ideas is through pictures, graphic

illustration or drawings. Details of engineering innovations and technical inventions

are hid in drawing for the purpose of safeguarding them. Technical/engineering

drawing is a means of communicating shapes, sizes, positions and proportion,

features and precision of physical objects.

The following descriptions can be used to describe the field of technical/engineering

drawing and presentation:

 Engineering drawing is graphical representation of physical objects and their

relationship.

 It is a universal language of engineering used in design processes for solving

problems quickly and accurately by visualizing objects and conducting analysis.

 It can also be said to be a graphic representation of objects and structures used to

solve problems which involve special relationships.

 It is a mode of thinking in which two-dimensional projections are used to visualize

three-dimensional situations.

 It is also a means of describing and defining processes which verbal expressions

cannot adequately conveyed.

 It is therefore an extension of language, and as such, an essential part of education

in a technological society.

 Engineering drawing communicate product design and manufacturing

information in a reliable and unambiguous manner regardless of language

1.2 Introduction

Drawings are used in all fields of engineering (agriculture, mechanical, civil,

architectural, electrical, aerospace, etc.). The types of drawings we will be creating in

this book are mechanical drawings, but the concepts are all transferable to the other

engineering fields. Engineering drawing is concerned with imparting precise

16 | P a g e

information hence it is understandable that neatness and accuracy should play an

important part in its practice. Beautifully copied engineering drawings are of little

value if the principles behind the work are not fully understood and applied.

These principles can be learned and practiced by using freehand, mechanical, or

computer aided design (CAD) methods. The ability to read drawing is the most

important requirement of all technical people in engineering profession. Below are the

basics concepts of engineering drawings.

1.3 Drawing language and standards

Engineering drawing is a form of language in its own right with rules and signs. Just

as it is applicable to any language, certain rules (or standards) must be followed in

producing any drawing. These rules/standards define how shapes and position of

object should be represented; for instance, the order of orthographic views and

different line types has rules and specific position in order to fully describe such

object. They also define how a part should be dimensioned or tolerance.

These standards are developed by some institutions or governing agencies specifically

set up for the purpose of formulating standards globally accepted and subject to

update on a 5 year basis. These organizations or governing agencies include:

1. BSI - British Standards Institute

2. ASME-American Society of Automotive Engineers

3. ANSI- American National Standards Institute

4. DIN - Deutsches Institut fur Normung (Germany)

5. ISO - International Standards Organization

The governing agency responsible for setting the mechanical drawing standards and

practices used in creating technical drawings of mechanical parts and assemblies is

the American Society of Automotive Engineers (ASME).Considering the ASME

standards for example, there are a number of documents published by ASME that

cover various aspects of mechanical drawings, here are a few of them:

1. ASME Y14.100 -2004 Engineering drawing practices

2. ASME Y14.1 -1995 Decimal inch drawing sheet size and format

3. ASME Y14.3M –Multi and sectional view drawings

4. ASME Y14.4M -1989 Pictorial drawing

5. ASME Y14.5M –1994 Geometric dimensioning and tolerance

6. ASME Y14.13M -1981 Mechanical spring representation

17 | P a g e

It is important to follow these standards to ensure your drawings are interpreted

correctly by others. Always consult the standard when in doubt!

1.4 Aim of drawing

The main purpose of engineering drawings is to communicate to other engineers,

machinists, etc. Drawings do the communication best merely because a picture is

worth a thousand words. Giving all of the information needed to make the product

and being accurate in that information is the main goal. Engineers are very picky

about their drawings and must pay attention to detail.

1.5 Types of drawing and views

There are terms commonly associated with graphic and engineering design drawings

in various forms and are meant to express different ideas as indicated below:

Diagram: This type of drawing depicts the function of a system represented in

drawing form

Sketching: This generally refers to freehand drawing without the aid of drawing

instrument

Drawing: This term usually means using instruments or drawing aids ranging from

compasses to computers to bring precision to an expressed conception in

form of graphics.

Drawing list: This is the list of cross references drawings that all combined to produce

an single product

Parts list (bill of materials): Part listing in drawing shows material, number/quantity

and provides reference number of various components

Assembly drawing: This shows how an individual parts are combined, refers to parts

list

Design layout drawing: This represents broad principles of feasible solution

Arrangement drawing: This type of drawing shows finished arrangement of assemblies,

including functional andperformance requirements

18 | P a g e

Detail drawing: This is a single part drawing containing all information for fabrication.

When there is a great disparity between feature sizes, or views are

overcrowded with dimensions, a detail view can be used to capture the

feature(s) of interest and display them in a removed view of greater scale.

Figure 1-1: Detail view

1.6 Engineering drawing requirements

Engineering drawing requirement are conditions that a specific drawing must meet in

order to conform to global standards in such field. Such requirements include:

1. Unambiguity and clarity: All engineering drawings must be unambiguous and clear.

Only one interpretation is possible.

2. Completeness : Every drawing must provide all information for all stages of

manufacture. i.e., detailed drawings, assembly drawings, bill of materials

3. Suitability for duplication: Such drawing must be suitable for duplication. It must

have suitable scale and clarity such that the drawing can be copied – even micro

copied – without losing quality.

19 | P a g e

4. Language independent: The drawing must be language or Words independent and

should only be used in the title block; words should be replaced by symbols.

5. Conformity to standards: Your drawing must be conformable to known standards.

Highest standards are ISO as numerous countries learn these rules.

1.7 Professional application of technical drawing

Figure 1-2 below give a list (not limited to the displayed groups) of professional

groups that are directly linked to engineering graphics in the execution of their daily

routing assignment.

Figure 1-2: Engineering drawing partners

1.8 Technical drawing and agricultural development

In the following areas, technical drawing plays very vital roles in agricultural

production practice.

20 | P a g e

1. Farm planning and field layout: Technical drawing provides the knowledge of

mapping out and field measurements when laying out foundation of structures.

2. Surveying: The knowledge of the topography of an area help in the determination

of the type of farming system to adopt.

3. Employment opportunities are created for draughtsman in the farm due to their

knowledge of technical drawing.

4. Farm structures design and construction were gained through the basic knowledge

of technical drawing

5. Implement design: Preliminary sketch of farm implements and tools aids their

design and construction in the workshop.

6. Machinery repairs: Faults diagnosis and repairs on some machinery can only be

done by tracing the diagram of the design details on the machine layout.

1.9 Steps to planning drawing

Unplanned drawing makes interpretation cumbersome and ambiguous bearing in

mind that drawing materials could be costly. Therefore starting engineering drawing

you should plan how to make the best use of your space. It is important to think about

the number of views your drawing will have and how much space you will use of the

paper. Consider the followings:

 Try to make maximum use of the available space.

 If a view has lots of detail, try and make that view as large as possible. If necessary,

draw that view on a separate sheet.

 If you intend to add dimensions to the drawing, remember to leave enough space

around the drawing for them to be added later.

 If you are working with inks on film, plan the order in which you are drawing the

lines. For example you don't want to have to place your ruler on wet ink

Exercise

1. The practice of draughtsmanship is critical to the development of the

agricultural sector. Critically justify this statement

2. In planning your routine daily schedule the place of graphic design and

illustration cannot the overemphasis. Enumerate some of the ways this will

enhance your plan.

3. Make a list of some engineering drawing standards applicable to your

profession and how each is applied to effective professional practice.

ResearchGate has not been able to resolve any citations for this publication.

145 6.3 Projection of points

Projection....................................................................................................................................................................................................................................................... Features

Features of projection....................................................................................... 145 6.3 Projection of points............................................................................................ 147 6.4 Projection of lines.............................................................................................. 147

156 7.4 Principles of first angle orthographic projection

...................................................................................................................................... Multiview Projection

Multiview projection........................................................................................... 156 7.4 Principles of first angle orthographic projection.............................................. 164

Society of Automotive Engineers

Asme-American

ASME-American Society of Automotive Engineers