The MMC of an external feature is defined as which of the following?

• A. Lower limit of the dimension
• B. Mean value of the dimension
• C. Upper limit of the dimension
• D. Standard deviation of the dimension

Answer: (C)

The Maximum Material Condition (MMC) for an external feature is defined as the condition in which that feature contains the maximum amount of material, which is determined by the upper limit of the dimension. For an external feature, this means the largest size allowable according to the specified dimension.

When assessing parts using MMC, it helps in achieving tighter controls and ensuring that the part can still function properly while allowing for assembly to take place. By focusing on the upper limit, designers and engineers can understand how much material is there when the part is at its maximum permissible size, which is crucial for ensuring fit and function in assemblies. This reflects the intent behind the MMC concept in GD&T, aiming to clarify tolerancing for manufacturing and inspection processes.