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True position tolerance to a face

True position tolerance to a face

True position tolerance to a face

Hello folks
First time on this forum, so I hope I'm in the right place.
OK, my question-
We have shiny new designer in the company, who is producing drawings with faces toleranced by true position back to other datums/planes. I'm perfectly familiar with true position of holes, but I've never come across this style of tolerancing a face. I don't understand how a face can be toleranced in this way, am I thick, or is my new designer nuts?
I hope that makes sense.


RE: True position tolerance to a face

Try forum1103: Drafting Standards, GD&T & Tolerance Analysis if you don't get the answer you need here.  Some pretty sharp folk over there that don't always look over here.

There are applications this kind of makes sense, for instance centering a notch/open slot on an width.

However, I'm not sure this is what you mean.

Can you post a sketch or something illustrating your point.

KENAT, probably the least qualified checker you'll ever meet...

RE: True position tolerance to a face

Beat me to the post, KENAT!

Believe it if you need it or leave it if you dare. - Robert Hunter

RE: True position tolerance to a face


   Position tolerances do not just go on round holes.  On a flat feature, they would apply in one direction only, and you would not apply the diameter symbol.

   Almost certainly, a profile tolerance would be more appropriate for a flat face of a part.

   Follow KENAT's advice about the GD&T forum.


RE: True position tolerance to a face

Thanks folks for such prompt replies. I'll check out the GD&T forum tomorrow, as well as including a sketch here to clarify. At home now, so I'll update in the morning.
Thanks again

RE: True position tolerance to a face

OK, here is a sketch (If I've managed to load it correctly) where there are 2 faces toleranced as true position. One is the end face of a valve feature, where there is a threaded cap assembled up to the face, and the other is a milled face on the right hand side to accommodate the two ports drilled through. Both are toleranced back to a fictional plane. Does that make sense in this context?

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