What is the difference between MMC and a projected tolerance zone?

What is the difference between MMC and a projected tolerance zone?

• A. MMC relates to the depth of the tolerance zone.
• B. A projected tolerance zone is defined by MMC.
• C. MMC relates to the size boundary used to calculate the tolerance; a projected tolerance zone is about the depth the zone extends.
• D. MMC and projected tolerance zone describe the same concept.

Answer: (C)

Maximum Material Condition defines the size boundary that governs how the tolerance is applied to a feature. It tells you where the feature sits on the size scale—for a hole that’s the smallest allowable diameter, for a shaft the largest diameter—and it sets how much “bonus” tolerance you might get if the actual size moves away from MMC. A projected tolerance zone, in contrast, adds a depth extension to the tolerance zone in the projection direction. It fixes how far the tolerance envelope is allowed to extend away from the part surface to simulate how the part will interact with mating features or fasteners in assembly. The depth of that extension is specified, not derived from the feature’s size. So the key difference is: MMC is about the size boundary used to calculate tolerance; a projected tolerance zone is about the depth the tolerance zone extends in projection. That’s why the correct distinction is that MMC relates to the size boundary used to calculate the tolerance, while a projected tolerance zone concerns the depth the zone extends.

Maximum Material Condition defines the size boundary that governs how the tolerance is applied to a feature. It tells you where the feature sits on the size scale—for a hole that’s the smallest allowable diameter, for a shaft the largest diameter—and it sets how much “bonus” tolerance you might get if the actual size moves away from MMC.

A projected tolerance zone, in contrast, adds a depth extension to the tolerance zone in the projection direction. It fixes how far the tolerance envelope is allowed to extend away from the part surface to simulate how the part will interact with mating features or fasteners in assembly. The depth of that extension is specified, not derived from the feature’s size.

So the key difference is: MMC is about the size boundary used to calculate tolerance; a projected tolerance zone is about the depth the tolerance zone extends in projection. That’s why the correct distinction is that MMC relates to the size boundary used to calculate the tolerance, while a projected tolerance zone concerns the depth the zone extends.