notes on introduction to technical engineering drawing

1. Basics of Engineering Drawing 1.1
INTRODUCTION
One of the most convenient ways to communicate, especially when discussing machines or their
components, is through engineering drawings. An engineering drawing is a type of drawing that
is technical in nature and is used to fully and clearly define the requirements for manufacturing
objects. It is usually prepared in accordance with basic principles and standardized conventions
for the layout, nomenclature, lines and symbolic representations. As these drawings follow
standard conventions, engineers can use them to communicate with each other anywhere in the
world. Therefore, engineering drawing is often called the universal language of engineers.
Learning to create and understand these drawings is, thus, very important for all engineering
students. In India, engineering drawings are prepared according to the basic principles, standard
conventions, symbolic representations and notations recommended by the Bureau of Indian
Standards (BIS).
1.2 DRAWING INSTRUMENTS
An engineering drawing can be prepared manually using drafting instruments or through c
omputer-aided drafting. The accuracy of drawings and speed of execution depend upon the
quality of drawing instruments. It is, therefore, desirable for students to procure instruments of
good quality.
The following drawing instruments are commonly used:
(i) Drawing board
(ii) 45° and 30°–60° set squares
(iii) Engineers’ scales
(iv) Protractor
(v) Irregular or French curves
(vi) masking tape
(vii) Drawing papers
(viii) Pencils(HB,3H)
(ix) Erasers
(x) (xvii) T-square

2. LETTERING
An engineering drawing is expected to provide complete information about the shape and size of
machine parts. This information is conveyed in the form of dimensions and notes, and that is
provided through the lettered text in the drawing. Thus, it is very important that the lettering in a
drawing also follow certain standards and guidelines. Legibility and uniformity, as well as ease
and rapidity of execution, are the fundamental requirements of good lettering.
GENERAL RULES FORLETTERING
The general rules of lettering are as follows:
(i) All letters should be written in capitals. Lowercase letters should be used only when
they are accepted in international usage for abbreviations. For example, we can use
mm for millimeter.
(ii) All letters and numerals should be written in such a manner that they do not touch
each other or lines.
(iii) All letters should be written in such a way that they appear upright from the bottom
edge, except when they are used for dimensioning. For dimensioning, they should
appear upright from the bottom edge, or they can be placed on the right-hand side of
the figure, or on the corner of the figure.
(iv) Letters should be spaced in such a way that the area between them appears equal. At
the same time, it is not necessary to keep the clearances between adjacent letters
equal. For example, letters like H, I, M and N, if adjacent, Words should be spaced
more widely should be spaced more widely than C, O and Q.
(v) Words should be spaced one letter width apart.
Figure 1 vertical lines

3. Figure 2sloping letters