is a Place for MMC on Threads
Many people believe that since
threaded fasteners generally center themselves in the threaded
hole, MMC (maximum material condition) is not applicable. MMC
is needed on threaded features to legitimize hard gaging.
Granted, where MMC is applied to threads the resulting
additional tolerance (bonus) will be very small and hard to
determine. Using MMC, however, does allow the use of hard
gaging to verify the position tolerance - even when the
projected tolerance zone is applied.
|To the right is
a drawing of a gage that could be used to inspect the
projected tolerance zone of the M10 threaded holes
relative to datum A stated in the lower of the two
single segment position tolerances. The values in
parenthese are the design values for this gage based on
the drawing. They do not include gage tolerance or wear
allowance. This gage is legitimate because MMC is
used to modify the tolerance.