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.
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?
I think you need something inline with this:
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 https://www.gdandtbasics.com/profile-of-a-surface
Answered by Jonathan R Swift on January 1, 2022
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