What is MMC (Maximum Material Condition) for a hole and for a shaft?

What is MMC (Maximum Material Condition) for a hole and for a shaft?

• A. For a hole, MMC is the smallest diameter; for a shaft, MMC is the largest diameter.
• B. For a hole, MMC is the largest diameter; for a shaft, MMC is the smallest diameter.
• C. MMC applies to both hole and shaft as average diameters.
• D. MMC is not related to hole/shaft.

Answer: (A)

Maximum Material Condition is the state in which a feature contains the most material. For a hole, that occurs when the hole is at its smallest permissible diameter, because the surrounding material is maximized. For a shaft, it occurs when the shaft is at its largest permissible diameter, since that is when the most material remains inside the feature. That’s why the correct description is: a hole’s MMC is the smallest diameter, and a shaft’s MMC is the largest diameter. The other ideas—hole at its largest, shaft at its smallest, MMC being an average, or MMC not related to holes or shafts—don’t align with the definition of maximum material condition.

Maximum Material Condition is the state in which a feature contains the most material. For a hole, that occurs when the hole is at its smallest permissible diameter, because the surrounding material is maximized. For a shaft, it occurs when the shaft is at its largest permissible diameter, since that is when the most material remains inside the feature. That’s why the correct description is: a hole’s MMC is the smallest diameter, and a shaft’s MMC is the largest diameter. The other ideas—hole at its largest, shaft at its smallest, MMC being an average, or MMC not related to holes or shafts—don’t align with the definition of maximum material condition.