A4

A3

A2

A1

A0

10

PRINCIPLES OF DRAWING* 2

2.1 Introduction

Engineering drawings are to be prepared on standard size drawing sheets. The correct shape

and size of the object can be visualised from the understanding of not only the views of it but

also from the various types of lines used, dimensions, notes, scale, etc. To provide the correct

information about the drawings to all the people concerned, the drawings must be prepared,

following certain standard practices, as recommended by Bureau of Indian Standards (BIS).

2.2 Drawing Sheet

Engineering drawings are prepared on drawing sheets

of standard sizes. The use of standard size sheet, saves

paper and facilitates convenient storage of drawings.

2.2.1 Sheet Sizes

The basic principles involved in arriving at the sizes

of drawing sheets are:

(a) X : Y = 1 : 2 , (b) XY = 1

where X and Y are the sides of the sheet. For a

reference size A0 (Table 2.1) having a surface area of

1 m^2 , X = 841 mm and Y = 1189 mm. The successive

format sizes are obtained either by halving along the

length or doubling along the width, the areas being

in the ratio 1:2 (Fig. 2.1).

2.2.2 Designation of Sizes

The original drawing should be made on the smallest

sheet, permitting the necessary clarity and resolution.

The preferred sizes according to ISO-A series (First

choice) of the drawing sheets are given in Table 2.1.

When sheets of greater length are needed, special

elongated sizes (Second choice) are used (Table 2.2).

These sizes are obtained by extending the shorter

sides of format of the ISO-A series to lengths that are

multiples of the shorter sides of the chosen basic

format.

Fig. 2.1 Drawing sheet formats

*Material for this chapter has been taken from BIS; SP–46: 1988.