Position Tolerance and MMC with Multiple Datum References

[Radius1]

I have two holes separated by a distance. Does the MMC apply to the hole on the left, or does the U and T position tolerance override to RMS ?

 

[Burunduk]

It's controlled at MMC relative to the [X,Y,Z] datum reference frame, RFS relative to the datum reference frame and RFS relative to the [T] datum reference frame.

 

[3DDave]

Are X, Y, and Z datum features?

There is no allowance for "overriding" a tolerance requirement. A tolerance may end up not being meaningful or useful, but that is a separate evaluation that, in this case, would require information about the relation between the referenced datum features.

 

[Radius1]

If the position tolerance of the right-hand hole is 3.0mm, would the tolerance zone in relation to datum T, then be a circle of 3.0mmm? Where would it's center be? what is throwing me off is the datum is on the edge of the hole.

 

[3DDave]

The right hand hole is in relation to [X|Y|Z], nothing to do with T.

 

[Radius1]

3DDave yes! I just got it, is to control the left-hand hole, in relation to the right hand.

 

[3DDave]

Difficulty in forming the question indicates a lack of understanding the problem.

Datum feature T appears to be tangent to a hole, so there is no control of orientation around the hole; same with datum feature U.

X, Y, Z aren't defined so who knows from that where this idea came from - but it's good to ask questions.