GD&T Symbol Guide
Least Material Condition
The size condition where a feature contains the least material: largest hole or smallest pin.
Definition
Least Material Condition is the limit of size where a feature contains the least amount of material.
For an internal feature such as a hole, LMC is the largest allowed size. For an external feature such as a pin, LMC is the smallest allowed size.
Application
Use LMC when preserving wall thickness, edge distance, or minimum stock is more important than assembly clearance.
It appears less often than MMC but is valuable for thin-wall holes and press-fit or contact-driven designs.
Pin And Hole At Least Material
LMC is useful when minimum wall thickness, edge distance, or guaranteed contact is the functional concern.
3D Tolerance Zone
LMC can create bonus tolerance as the feature departs from least material size.
Inspection Method
Compare actual feature size to the LMC limit, then add any departure from LMC as bonus tolerance where the callout permits it.
No-go gaging concepts are often used when ensuring a feature is not too loose or too small.
Worked Check: Hole Near An Edge
A hole has LMC size 10.20 mm and position diameter 0.15 at LMC. The actual hole is 10.12 mm and position error is 0.20 mm.
Bonus
10.20 - 10.12 = 0.08 mm
A smaller hole has more material remaining near the edge.
Available
0.15 + 0.08 = 0.23 mm
The geometric tolerance grows by the departure from LMC.
Compare
0.20 <= 0.23
The measured error is within the available tolerance.
The hole passes while maintaining the intended minimum material around it.
Comparison Table
| Feature | MMC | LMC | Typical Concern |
|---|---|---|---|
| Hole | Smallest | Largest | Wall thickness at LMC |
| Pin | Largest | Smallest | Guaranteed contact at LMC |
| Slot/tab | Most material | Least material | Boundary control |
Notes
LMC applies to features of size, not arbitrary surfaces.
MMC protects worst-case assembly clearance; LMC protects least-stock or minimum-contact conditions.