Two ANSI approved systems indicate dimensions on drawings: the aligned
dimension and the unidirectional dimension system. Select one system of
dimensioning to use throughout the drawing. You may show dimensions
with either whole numbers and fractions, decimals, or metric units of
ALIGNED DIMENSIONS: Drawings made with aligned dimensions have all
figures and notes aligned with a dimension line so that all read from the sides
or edges of a drawing. The most common are read from the bottom and
right side. Aligned dimensions are sometimes referred to as pictorial
Figure 3-24 is an example of aligned dimensions.
UNIDIRECTIONAL DIMENSIONS: In the unidirectional dimension system,
all dimension figures and notes are lettered horizontally and are read from the
bottom of the drawing. The unidirectional dimension system is preferred
over the aligned system because it is easier to read and understand.
Figure 3-25 is an example of the unidirectional dimension system.
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