Lines and linework

Two thicknesses of line are recommended for manual and CAD drawings. A wide line and a narrow line in the ratio of 2:1.

Standard lead holders, inking pens for manual use, and those for CAD plotters are all available in the following millimetre sizes: 0.25, 0.35, 0.5, 0.7, 1.0, 1.4 and 2.0.

Line thicknesses of 0.7 and 0.35 are generally used and will give good quality, black, dense and contrasting lines.

Table 5.2, shows applications for different line types which are designed to obtain a good professional finish to a drawing.

Various combinations of line thickness and type are shown on the mechanism in Fig. 5.2. (Circled numbers relate to the line types in Table 5.2.)

Figure 5.3 shows part of a cone and if the complete cone was required, for example for dimensioning purposes, then the rest would be shown by adding narrow continuous lines which intersect in a dot.

Table 5.2 Types of line


Description & Representation



Continuous wide line

Visible edges and outlines


Continuous narrow line

1 Dimension, extension and projection lines

2 Hatching lines for cross sections

3 Leader and reference lines

4 Outlines of revolved sections

5 Imaginary lines of intersection

6 Short centre lines

7 Diagonals indicating flat surfaces

8 Bending lines

9 Indication of repetitive features


Continuous narrow irregular line

Limits of partial views or sections provided the line is not an axis


Dashed narrow line

Hidden outlines and edges

Long dashed dotted narrow line

1 Centre lines.

2 Lines of symmetry

3 Pitch circle for gears

4 Pitch circle for holes

Long dashed dotted wide line

Surfaces which have to meet special requirements


Long dashed dotted narrow line with wide line at ends and at changes to indicate cutting planes r~---


Note BS EN ISO 128-24 shows a long dashed dotted wide line for this application


Long dashed double dotted narrow line

1 Preformed outlines

2 Adjacent parts

3 Extreme positions of moveable parts

4 Initial outlines prior to forming

5 Outline of finished parts

6 Projected tolerance zones


Continuous straight narrow line with zig zags

A, "A.

Limits of partial or interrupted views;

Suitable for CAD drawings provided the line is not an axis

If it is necessary to show the initial outline of a part before it is bent or formed, then the initial outline can be indicated by a chain thin line which is double dashed. Figure 5.4 shows the standard applied to a metal strip.

Figure 5.5 shows the method of detailing a long strip of metal which has 60 holes in it at constant pitch. There would be no need to detail all of the component and this illustration gives one end only. The line to show the interruption in the drawing is narrow continuous and with the zig-zag cutting line indicated by the letter J.

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