Watch the Placement of Datum Identification Symbols and the
Feature Control Frames for Straightness, Perpendicularity,
Parallelism and Angularity!
When applying the above to features
of size, the placement of the symbol or callout can greatly
change the meaning. If the symbol or control is associated
with the size dimension, the feature's axis or center plane is
being identified or controlled. If the symbol or control is
associated with the surface of the feature of size, it is
identifying or controlling the surface - not the axis or
center plane. In this example both the datum feature symbol
and the perpendicularity apply to the feature's center plane.
Notice that there are two center planes.
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In the second example,
both the datum feature symbol and the perpendicularity
apply to the left surface of the slot. |
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