The Y14.5 Standard
tells us that we cannot apply the MMC modifier to a profile
tolerance because it is a surface control. We can, however,
apply MMC or LMC to the datum references of a profile
tolerance where the datum features are features of size. Here
the secondary and tertiary datum features are features of
size. Applying MMC to these features means that the part may
be shifted on the datum feature virtual conditions in order to
bring the features into their profile tolerances. The lower
illustration is of a possible overlay chart that could be used
if the part is inspected on an optical comparator. You can see
that the part has been shifted on the datum feature virtual
conditions in order to bring the features into their profile
tolerances. If the datums had applied RFS, this part would not
pass inspection. This is easy to do with an optical
comparator. This is not easy to do in an open set-up and on
most coordinate measuring machines. It is important to know
what inspection method will be used when assigning geometric
tolerances and material condition modifiers.
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DIMENSIONING AND TOLERANCING
PER
ASME Y14.5M-1994 AND ASME Y14.41-2003
CAD FILE
IS BASIC |
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