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GD & T – Material Condition Modifiers



What are Material condition modifiers?

  • GD&T on holes (and shafts) provides a powerful tool for increasing inspection yield without trial-and-error fitting or binning.
  • Used when the size of the feature interacts with its location.
  • If ⓜ the symbol appears after the tolerance, then the specified tolerance holds only at maximum material condition.
  • As the feature departs from MMC, the amount of departure can be added to the position tolerance.
  • MMC is commonly used for clearance-type applications.



  • This feature control frame specifies the positional tolerance zone as a circle of diameter .010 at MMC, centred according to the basic dimensions given.
  • The tolerance zone's size depends on the size of the hole.
    • MMC of hole = .250
    • LMC of hole = .255
  • Similarly, if Ⓛ symbol is used, the stated tolerance holds at least material condition (LMC). As the part departs from LMC, the amount of departure is added to the position tolerance.
  • LMC is commonly used for loose fits.
  • If no modifier is specified, (or ⓢ symbol in past practice) then the stated tolerance holds regardless of the material condition of the feature. This is called RFS – regardless of size.
  • RFS is commonly used for pressed fits.



The logic behind bonus tolerances

  • Taking an example for MMC