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There are two basic methods of dimensioning: progressive dimensioning and continuous
dimensioning.
1. Progressive dimensioning — In this method of dimensioning, all dimensions on the
drawing are shown from a common base line, as shown in Fig. 1.19. Cumulative error is avoided in
this method.

Figure 1.19 - Progressive dimensioning

2. Continuous dimensioning — In this method, dimensions are arranged in a straight line. An
overall dimension is placed outside the smaller dimension. One of the smaller dimensions is
generally omitted which is least important, as shown in Fig. 1.20.

Figure 1.20 - Continuous dimensioning

Finally, there are the general rules for dimensioning. The following rules should be observed
while dimensioning:
1. Standard sizes of letters and figures should be used.
2. All dimensions should be specified in mm.
3. As far as possible dimensions should be placed outside the views.
4. Dimension lines should not run in the direction included in the hatched area.
5. Dimensions should be taken from visible outlines rather than from dashed lines.
6. Dimensions should be given from a base line, a centre line, an important hole, or a
finished surface which may be readily established.
7. Dimensions should be quoted only once in one view.
8. Overall dimensions should be placed outside the intermediate dimensions.
9. Dimensions should be placed outside a sectional view.
10. Dimension line should not cross. Also dimension lines and extension lines should not
cross.
11. When there are several dimension lines, the shorter dimension should be nearer the view.
12. Do not use outlines for dimensions.

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