INTRODUCTION TO ENGINEERING DRAWING

1.1 Introduction

Look at the fig. shown on the right side. What is it called in English, in Hindi and in your mother tongue? It is a Parrot in English, Thotha in Hindi and some other in your mother tongue. The fig. is same but depending on the language it will be called in different ways. Before there in no language and script the idea of the people are communicated by the pictures only. The picture is a drawing and communicates some message, communicating a message is called a Language.

1.2 Importance of Engineering Drawing

Engineering Drawing is also a language which communicates its ideas. Engineering drawing is Engineers language in which the communication between Engineer’s of different Countries and between top level Engineer’s to lowest working community will take place. Engineering Drawing is called Universal language of Engineer’s.

Engineering Drawing is a two dimensional representation (on Paper which have two dimensional) of a three dimensional object in this universe. In general, it provides necessary information about the Shape, Size, Surface roughness, Material used, Manufacturing process, Assembly etc of the object of the Machine component.

1.3 Need for preparing for Drawing as per standards – SP – 46 – 1988

Every language will have its own grammar or rules. When Engineering Drawing is called as a language of Engineer’s it will also have its grammar’s or rules. The common rules and methods adapted are similar throughout the world and makes the communication between various levels of people involved in Engineering Design, Production, Management, Servicing, Maintenance, etc Simple, effective and efficient.

For this purpose, Bureau of Indian Standards (BIS) adopted the international standards on code of practice for Drawing. The other foreign standards are: DIN of Germany, B.S of Britain and ANSI of America.

1.4 Role of Drawing in Engineering Education

In this modern world, Engineering Drawing has come to stay as the most important branch of Engineering. It is rightly called “Language of Engineer’s”. With this language, the thoughts, ideas and designs regarding objects existing in this universe can be represented through different lines. It not only saves the time and labour, but also gives complete information of the object to be produced of manufactured. It is therefore, very essential for all disciplines of Engineering students to have a thorough knowledge of Engineering Drawing and its wide applications in Engineering fields like Civil, Mechanical etc. Based on these principles, other

drawings like Building drawing, Machine drawing, Production drawing, Computer Aided Drawing, etc., are developed in various branches of Engineering.

1.5 Scope of the Subject on Engineering Drawing

The subject matter presented here relates to basis engineering drawing and is intended to be used for class room training of the beginners of the engineering curriculum at diploma level. It mainly deals with the geometrical drawing. It is the art of representation of geometrical objects on a drawing sheet and is the fundamental of all engineering drawings.

Plane geometrical drawing deals with the representation of objects having two dimensions. Solid geometrical drawing deals with the representation of objects having three dimensions. Geometrical drawing is the basis for various specialised types of drawings, related to different fields of engineering.

Throughout the book, the problems have been treated in first angle projection and all drawings as well as the text matters are in conformity with the latest code of practice, recommended by Bureau of Indian Standards, SP. 46 – 1988.

1.6 Object of the subject of Engineering Drawing

A practice speaks thousands of words. A message conveyed by a picture on a sketch or a sign in much effective than a message conveyed by word. That is why, since before the start of civilization, human beings used the language of drawing to convey their ideas. With the progress of technology, man felt the need for a standardization of drawing language so that it could be understand globally. Drawing is therefore included in every engineering curriculum to train the student to express his ideas in a manner which is easily understood by others.

A typical study of the drawing course led to the following observations 1. It develops a type of discipline in graphical techniques.2. It develops ability to analyse and communicate ideas.3. It helps in imaging the proper size, shape and form of an object.4. It develops capacity of reasoning and judgement.5. It helps in the study of other engineering subjects.

1.7 I.S.O and B.I.S Standards

The BIS is the National Standards Body formed by the Government of India on 1 April 1987, replacing Indian Standard Institution (ISI) existing earlier. The objective of BIS is to foster the industrial and commercial growth of the country by developing globally acceptable standards for products. It works in association with other standard – developing organizations worldwide, in particular with the International Standards Organization (ISO).

BIS has recommended and published various standards for technical drawings. These standards are available in the form of IS codes and Special Publication (SP) 46: 2003. The

readers are strongly encouraged to see and adopt these standards in drawing practice. This book uses the following ISs:

IS 1444: 1989 ENGINEER’S PATTERN DRAWING BOARD – SPECIFICATION IS 10711: 2001 TECHNICAL PRODUCT DOCUMENTATION SIZES AND LAYOUT

OF DRAWING SHEETSIS 3221: 1966 SETS FOR DRAWING INSTRUMENTSIS 10713: 1983 SCALESIS 10714: 2001 LINESIS 9609: 2001 LETTERINGIS 15021: 2001 PROJECTION METHODSIS 10714: 1983 SECTIONS AND OTHER CONVENTIONSIS 11669: 1986 GENERAL PRINCIPLES OF DIMENSIONING ON TECHNICAL

DRAWINGSWhere ISs are not available, relevant international standards may be adopted.

1.8 Link between Engineering drawing other subjects of study

While teaching majority of engineering subjects, figures or sketches of related objects, machines or systems are made use of, to explain the principles of operation, relation between the parts, etc. unless the figures are presented, following the norms of draughting practice, the required information is not fully conveyed. For example in Theory of Machine subject for understanding Cam Profiles or for Drawing Cam profiles drawing subject plays important role. Like this for understanding Design of Machine Members, Thermal Engineering, Machine Drawing subjects and for Civil Engineering Building Drawing surveying subjects drawing subject is very important. Hence, the knowledge in engineering drawing is useful in understanding other engineering subjects as well.

REVIEW QUESTIONS

1. Why Engineering Drawing is called as Universal Language of Engineers?

2. Explain the role of Drawing in Engineering education?

3. Name the various types of engineering drawings?

4. Discuss the relation between drawing and other engineering subjects?

5. What are the observations learn in a typical study of the drawing course?

6. List out the various IS s specification of practice for drawing?