Understanding Maximum Material Condition

Our Question Line Video for today is in response to a student’s question regarding Maximum Material Condition. This student wanted to know, “Why isn’t Maximum Material Condition always just the largest size the feature can be?” Jason gives us a delicious way to remember the MMC state for a feature of size in the video below!

Every feature of size has a Maximum Material Condition (MMC) and a Least Material Condition (LMC). The MMC is the state where the maximum amount of material exists within the dimensional tolerance. Likewise, the LMC state is where the least amount of material exists within the dimensional tolerance.

Our student asked why the MMC of a feature of size is not always the largest allowable size for that feature. This depends on whether the feature is internal or external. To explain, let’s think about a donut!

Say the manufacturer of the donut requires a diameter of 5.000 +/- .125 on the OD of the donut, and 1.500 +/- .125 for the ID of the donut. If we want the maximum amount of donut, what dimensions would that equate to?

Maximum Material Condition of the Donut

To get the most donut for our money, we would want a donut with the largest outer diameter and the smallest inner diameter. So, the Maximum Material Condition for the external feature (the OD) would be 5.125, and the MMC for the internal feature, the donut hole, would be 1.375.

If we were to picture the Least Material Condition for this donut, we would do the opposite. To have the least amount of donut would require the smallest OD dimension, and we would want the donut hole to be as large as possible. Therefore, the LMC for the OD of the donut would be 4.875, and the LMC for the ID of the donut would be 1.625.