252
Exploring Drafting
Fundamental Rules for
Dimensioning
For clarity, dimensions should conform to
the following general rules:
1. Place location and size dimensions on
the views that show the true shape of the
feature being dimensioned (the primary
views). See Figure 10-8. The true shape
of the feature appears on the view that
shows the feature as negative mass. Do
not locate or give the size of features in
secondary views. A secondary view is a
Simply put, when dimensioning an object,
apply the following steps:
1. To identify the overall dimensions, tell
how large the object is overall. Describe
the positive mass. Provide the overall
width, height, and depth dimensions.
2. To identify the location dimensions,
tell where the features of the object are.
Locate the negative masses.
3. To identify the size dimensions, tell how
large the features (negative masses) are.
While following the previous steps, make
accurate and consistent use of several funda-
mental dimensioning rules. These are discussed
next.
When identifying location dimensions, as
much as possible, try to locate the features
with respect to the original edges of the
original mass of the object. Try not to locate
them with respect to other features. Doing
this has a tendency to either dictate the order
of procedure for manufacturing or cause the
person making the part to perform mental
mathematics during the layout procedure.
Note
Goodheart-Willcox Publisher
Figure 10-7. Object dimensions can be classified as overall, location, or size dimensions. The three features of this
object are described by the size dimensions.
6
2
Preferred
2
6
Avoid
2 2
Goodheart-Willcox Publisher
Figure 10-8. Location and size dimensions are placed
in views that show features in their true shape.
Copyright Goodheart-Willcox Co., Inc.