PRIN. OF DRAFTING AND SHOP DRAWINGS - OD1641 - LESSON 1/TASK 4
a. Dimensions. Dimensions are placed on a drawing by using a system of extension
lines, dimension lines, leader lines, and arrowheads.
Figure 68 illustrates how
these various kinds of lines are used for dimensioning.
FIGURE 68.
EXTENSION, DIMENSION, AND
LEADER LINES.
(1) Types of Lines.
The lines are defined as follows:
(a) Extension lines are used to indicate the extension of an edge or point to
a location outside the part outline.
(b) Dimension lines show the direction and extent of dimension.
(c) Leader lines are used to direct an expression, in note form, to the
intended place on the drawing. The leader line should terminate in an arrowhead or
dot.
(d) Arrowheads are used to indicate the ends of the dimension lines and the
ends of some of the leader lines.
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