Key Points
The least material condition (LMC) of a feature is the biggest hole or smallest pin. An LMC modifier may be applied by placing the circle L symbol in the feature control frame behind the tolerance. This allows additional geometric tolerance as the feature’s size departs from its LMC.
The feature control frame below states that the holes must be positioned within 0.6 at the feature’s LMC. The LMC for the hole is 12.3 diameter; the 0.6 position tolerance applies at this size. As the hole departs (gets smaller) from its LMC size, it is allowed additional position tolerance equal to its departure from LMC. Industry often calls this departure from LMC “bonus tolerance”. The holes could have as much as 1.2 diameter position if they are produced at their MMC size of 11.7. See table below.
The LMC modifier allows additional position tolerance as the features depart from their LMC.
Example Drawing
