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There Is a Place for MMC on Threads
(In accordance with Y14.5M-1994 standard)

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 parentheses 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.

Back to Tips Tip added Jun 2003