Coplanarity Profile Callout Confusion

Engineering Asked on January 1, 2022

From Krulikowski (1997), the callout for several coplanar surfaces using the Profile symbol is done by using two surfaces to establish datum plane A-B and then tolerancing the remaining coplanar surfaces in reference to A-B.

Can other non-coplanar features reference this datum plane A-B as I would a normal datum? See below for example.

enter image description here

In the O-ring groove above (2.5 x 1.6), the callout on the left is for coplanarity. The callout on the right is for location and form, NOT coplanarity. I guess it would be obvious that it is not coplanar, but something about it looks off.

Is referencing datum A-B for non-coplanar features legal, illegal, or just plain bad notation? Or is it just a matter of preference?

2 Answers

I think you need something inline with this:

enter image description here

Note that the datum A is identified by using an indicator under the callout. A-B could equally be used with the same meaning if you identify the two surfaces.

You can have more explanation in ASME 14.5:2018 figure 6-6.

Answered by Jean-François MAUREL on January 1, 2022

This is fine, but not typical for cylindrical faces.

The Profile GD&T symbol describes a 3D tolerance zone around the face, and as such is typically used for complex surfaces where other symbols cannot be used. See

Answered by Jonathan R Swift on January 1, 2022

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