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Once datums have been established,
other features must be located with respect to the datums.
Often those applying GD&T will use orientation (b,f,a) and
form (c,u,e&g) controls and forget to control the
location. Features are located geometrically using profile of
a surface (d), position(j) and, as last month's Tip explained,
sometimes runout (h or t). These locating controls
automatically provide orientation and, with the exception of
position, form control. Form is provided by the size dimension
when using position. The orientation and form controls should
only be pulled out of the toolbox to be used as refinements.
The geometric controls shown in blue come for "free" with the
general Profile of a Surface.
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