264
Exploring Drafting
drawings with both inch and metric units. See
Figure 10-32.
Dual dimensions are presented using one
of two methods, the position method or the
bracket method. See Figure  10-33. The inch
dimension is placed fi rst on drawings of
products to be made in the United States. The
metric dimension is placed fi rst on drawings
of products to be made where the SI Metric
system is the basic form of measurement.
• Metric dimensioning with a conversion
chart.
• Metric dimensioning (metric units only).
• Undimensioned master drawings.
Dual Dimensioning
The use of dual dimensioning was the fi rst
method devised to dimension engineering
A
Preferred
Vertex
Avoid (Unless angle is unknown)
B
Object
feature
Avoid
Original edge
Dimension locates
vertex with respect
to square feature
(not original edge)
C
Goodheart-Willcox Publisher
Figure 10-30. Dimensioning angles. A—Locate the vertex of the angle and give its size. B—If the angle is
unknown, providing a linear distance (as shown) is acceptable. C— Locate angles with respect to the original
edges of the object, not with respect to other features.
1 _
4
1 _
8
.125
Goodheart-Willcox Publisher
Figure 10-31. Depending on the space available between extension lines, the arrowheads, dimension numeral, or
entire dimension may be placed outside the extension lines.
Copyright Goodheart-Willcox Co., Inc.