Osakue - Introductory Engineering Graphics

INTRODUCTORY ENGINEERING GRAPHICS

INTRODUCTORY ENGINEERING GRAPHICS

EDWARD E. OSAKUE

Introductory Engineering Graphics

Copyright Momentum Press, LLC, 2018.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any meanselectronic, mechanical, photocopy, recording, or any otherexcept for brief quotations, not to exceed 400 words, without the prior permission of the publisher.

First published by Momentum Press, LLC

222 East 46th Street, New York, NY 10017

www.momentumpress.net

ISBN-13: 978-1-94708-360-8 (print)

ISBN-13: 978-1-94708-361-5 (e-book)

Momentum Press General Engineering and K-12 Engineering Education Collection

Cover and interior design by Exeter Premedia Services Private Ltd., Chennai, India

10 9 8 7 6 5 4 3 2 1

Printed in the United States of America

ABSTRACT

Introductory Engineering Graphics concentrates on the main concepts and principles of technical graphics and provides users with the information they need most in an easy and straightforward manner. The chapters and topics are organized in a sequence that makes learning a gradual transition from one level to another. However, each chapter is presented in a self-contained manner and may be studied separately. In each chapter, techniques are presented for implementing the topics treated. , the heart of drafting, and practical information is provided for creating them. The Appendices provide introductory discussions about screw fasteners, general and geometric tolerancing, and surface quality and symbols.

This book is designed as a material for instruction and study for students and instructors of engineering, engineering technology, and design technology. It should be useful to technical consultants, design project managers, computer design drafting (CDD) managers, design supervisors, design engineers, and everyone interested in learning the fundamentals of design drafting. The book is written with full cognizance of current standards of American National Standards Institute/American Society for Mechanical Engineers (ANSI/ASME). The style is plain, and discussions are straight to the point. Its principal goal is meeting the needs of first- and second-year students in engineering, engineering technology, design technology, and related disciplines.

KEYWORDS

auxiliary views, CDD, design, dimensioning, graphics, isometric views, multiview drawings, orthographic projection, section views, shape construction, technical, working drawings

CONTENTS

The technical educational environment has changed dramatically in the last few decades. Instructors and students in design technology, engineering technology, engineering, and related disciplines are faced with limited study time, but with increasing information for training in technical graphics. Contact hours for lectures and laboratories in technical graphics have been shrinking, but product design continues to grow in complexities, and the time to market continues to shrink! New design tools that are largely computer based come into the workplace at astonishing speed. There are more materials to cover, but in fewer contact hours. These challenges need serious considerations, and this book is written to address them.

Instructors are free to use any CDD package of their choice to implement the concepts and principles discussed in each chapter. They may first give a lecture on the chapter and ask the students to answer the chapter review questions. A quiz on the chapter can be created and administered by the instructor before the chapter exercises are attempted. An alternative approach is to assign a chapter as a reading assignment with the students required to answer the chapter review questions before the lecture. A quiz can then be administered after the lecture. These approaches should help the students to understand the rules before playing the game, that is doing the exercises.

Introductory Engineering Graphics is highly condensed so as to maximize the use of production materials. I hope students and teachers, the primary audience, will find the book a valuable resource and enjoy using it. I am deeply grateful to Momentum Presss dedicated team of reviewers for their professional critique and invaluable suggestions. Many thanks to the hundreds of students who have taken my drafting courses for their suggestions and critiques over the years. Please feel free to inform me of any error found and comment(s) for improvement will be highly appreciated. All communications should, please, be channeled through the publisher.

Edward E. Osakue
April, 2018.

1.1 INTRODUCTION

Drafting is the process of creating technical drawings consisting of two-dimensional (2D) images and annotations, and the term draughting is used to describe the language of drafting in this book. Draughting defines the terminology, symbology, conventions, and standards used in drafting. It is the universal technical language that is used for clearly and accurately describing the form, size, finish, and color of a graphic design model for construction or recording. Draughting guidelines deal with standards and conventions in drawing media, lettering, linestyes, projection standards, plot scales, dimensioning rules, sectioning rules, and so on. In this chapter, we will concentrate mainly on drawing media, lettering, and linestyles, while others will be discussed in the appropriate chapters.

The 2D images in drafting are constructed from lines and curves, while annotations are composed from characters. 2D technical drawings may be created using axonometric and perspective principles. Axonometric drawings are 2D drawings obtained by applying orthogonal projection principles to three-dimensional (3D) objects and include orthographic, isometric, dimetric, and trimetric drawings. Pictorial drawings such as isometric and perspective drawings mimic 3D objects in appearance, but are made of 2D entities by composition. Most technical drawings are of the orthographic and isometric types, which are the focus of this book. Some standards and conventions apply to both lines and characters in drafting, and they must be learned and used correctly. Therefore, drafting skills involve learning to correctly apply the rules of draughting in creating acceptable or industry standard technical drawings. Proficiency in drafting involves being able to create high-quality technical drawings, therefore, becoming proficient in drafting must be a commitment executed with determined effort.

1.2 CONVENTIONS AND STANDARDS

Draughting principles, conventions, rules, and standards help to minimize misinterpretations of drawing contents and eliminate errors in the communication of technical ideas. Conventions are commonly accepted practices, methods, or rules used in technical drawings. Standards are sets of rules established through voluntary agreements that govern the representation of technical drawings. Standards ensure clear communication of technical ideas. The design drafter must study and understand these conventions and standards and learn to apply them correctly in practice. For example, good technical drawings are achieved by following some principles such as:

Keeping all lines black, crisp, and consistent.

Using different linestyles.

Ensuring clarity in linestyle differences such as in thickness or line weight.

Ensuring dashes have consistent spacing with definite endpoints.