Your Source for GD&T Training and Materials

Back to GD&T Tips

Threads - MMC
   There 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. 

Back to GD&T Tips