Applying MMC to datum references

We have already talked in a previous article about the problems of tolerancing the various elements of plans correctly. Today, this GD&T video from Tec-Ease will show us how to apply MMC to profile datum references. Bellow is the written transcription of this video:

I am often asked if MMC can be used with profile. The answer is: sort of. You are not allowed to ever apply MMC to the profile tolerances; you are, however, allowed to modify datum features referenced in the profile tolerance, provided that they are features of size.
Here, datum B and C have been modified in MMC. This does not change the profile tolerance on, which is still of 0.4. It does allow the profile tolerance to be flawed a bit when the datum features are made larger than the virtual conditions.
Let us say this part is to be inspected using an overlay and an optical comparator. If the datum features B and C had been applied at our first, the part shelter could not move or be flawed on the datum simulator.
Since datum B and C are modified in MMC, the overlay includes the virtual conditions of datum features shown here in red, and the inspector could float the outline of the part around to bring it into the profile zone of 0.4, provided that the datum features did not violate their virtual conditions.

Related articles:

• GD&T_Tolerance those slots right
• GD&T_Datum Features Must be Referenced to be Used
• GD&T_Datum Features Have Axes
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