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Use Composite Tolerances to
Control the Feature-to-Feature Relationship
(in accordance with the ASME
Y14.5-2009 standard)
PDF of This Tip
Another
Composite Tolerancing Tip
Some folks continue to give
the orientation tolerances more power than they
deserve. They orient but they do not locate.
Therefore, the location of the two holes and their
location to each other is specified by the position
tolerance. From The GD&T Hierarchy, you know that
locating tolerances like position and profile of a
surface also control orientation. But, we can refine
this orientation by pulling the appropriate
orientation controls (parallelism, perpendicularity
and angularity) from our toolbox.
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this drawing the orientation of the 2 holes
relative to the 1st and 2nd datum planes is
refined with parallelism, but they are free
to float relative to one another within
their position tolerances of 0.5.
Parallelism is an orientation tolerance and
never locates anything. It does not tighten
the location within the pattern. |
If you
want to tighten the location of the holes
within the pattern, as well as the
parallelism, you have to use composite
position. The datum features referenced in
the lower segment of a composite tolerance
are there to tighten up the orientation.
Since this is a position control, the
location of the features within the pattern
is also controlled, in this case, to Ř0.2. |
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This is
much easier to illustrate in an animation, so be
sure to click on the video icon above.
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