Engineering Drawing Principles and Applications

Introduction

The topics covered in this chapter are meant to introduce the readers to various types of lines, lettering and layout of sheets, which are used in engineering drawing.

Lines

A line is the basis of engineering drawing; a set of conventional symbols representing all the lines needed for different purposes may well be called an alphabet of lines. In engineering drawing each line has specific measurements and functions. The Bureau of Indian Standards (BIS) has recommended various types of lines and their applications in technical drawing. These are exhibited in Table 2.1.

Lettering

Lettering is an important feature of all engineering drawings, which is meant for indicating notes, dimensions, etc., on a drawing. Despite the fact that a drawing may be made accurately and neatly, poor lettering may lead to deteriorated appearance and sometimes make the drawing useless. Therefore, lettering on a drawing needs to be legible, neat in appearance and in appropriate style. The subsequent sections describe various types of letters.

Single Stroke Letters

BIS has recommended single stroke lettering for use in engineering drawing. In single stroke letters, the thickness of a letter is such that it is obtained in one stroke of the pencil. Horizontal line (stroke) is from left to right, and vertical or inclined lines (strokes) are from top to bottom.

Single stroke letters are of two types:

• • Upper case or capital letters

• • Lower case or small letters

Again both of them are further sub-divided into two categories:

• • Vertical

• • Inclined

In vertical lettering, stems are perpendicular to the line of lettering, whereas in inclined lettering, stems make a slope of 75° to the horizontal. Normally, letters are nominated by their height; therefore height of the letters enables us to classify the letters as

• • Lettering ‘A’

• • Lettering ‘B’

The standard ratios for line thickness (d) to height (h), d/h, as 1/14 and 1/10 are most prevalent as they result in a minimum number of thicknesses, as given in Table 2.2.