These two terms are used in GD&T drawings.
MMC is the MAXIMUM MATERIAL CONDITION
and
LMC is LEAST MATERIAL CONDITION
Suppose you are given a drawing of HOLE and a SHAFT with tolerance given on it.
- Then MMC condition would be the maximum size of the shaft and minimum hole size.
- The LMC condition would be minimum shaft size and maximum hole size.
According to rule 1 the part has perfect form at MMC.
Let us take an example in order to understand it.
Suppose I have the following drawing find out the MMC and LMC condition for it.
Shaft:
Hole:
Now at the MMC condition the dimensions would be as follows:
- Shaft: 30.05mm (Max Dia.)
- Hole: 29.95mm (Min Dia.)
The dimensions at LMC condition would be as follows:
- Shaft: 29.95 (Min. Dia)
- Hole: 30.05 (Max. Dia)
In brief you can say that the MMC condition is the one in which maximum material is used in the assembly and LMC is the condition in which least mateial is used in the assembly.