Maximum Material Condition
Least Material Condition

  • When a part feature contains the maximum amount of material allowed within the specified size limits, it's said to be in its maximum material condition.

  • An external feature, such as a fastener, is in its maximum material condition when it's at its upper size limit.

EXAMPLE: The MMC of this fastener is.747.

  • An internal feature, such as a hole, is in its maximum material condition when it's at its lower size limit.

EXAMPLE: The MMC of this hole is .750.
  • When a part feature contains the least amount of material allowed within the specified size limits, it's said to be in its least material condition.

EXAMPLE: The fastener is in its least material condition when it's at its lower size limit of .744. The hole is in its least material condition when it's at its upper size limit of .753.
  • The material condition of the part is significant in geometric dimensioning and tolerancing. In many cases, the difference between a part's actual size and its maximum material condition becomes a bonus tolerance, making it larger.

This bonus tolerance is one of the advantages of GD&T.

Types of Fit

  • The specified size limits of mating part features are intended to produce a particular type of fit.

  • When the specified size limits of mating part features always result in clearance at assembly, the parts are said to have a clearance fit.

EXAMPLE: In the drawing obove, even when the fastener is at its MMC size of .747 and the hole is at its MMC size of .750, there is clearance.

  • When the specified size limits always produce interference at assembly, mating part features are said to have an interference fit.
EXAMPLE: In the center drawing, even when the fastener is at its LMC size of .5012 and the hole is at its LMC size of .5007, there is interference.
  • When mating part features do not fit together in their maximum material condition, but do fit at some point as they approach their least material condition, they are said to have a transition fit.
EXAMPLE: In the drawing on the right, when the fastener is at its maximum material condition size of .5003, it will not fit the hole at its MMC size of .5000. However, when both features are manufactured at their least material condition size, they will fit together.
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