Composite Tolerance

I am having trouble understanding composite tolerance, especially when it comes to a bolt hole pattern like this. I am wondering how you would dimension these true positions. Here's my idea using legacy dimensioning:

Level and translate to A, rotate to B, and report the position of 1 hole (any hole?...lets say the 12'O'Clock hole) and give it a .001 tolerance. Then, would I stay leveled to A&B, translate to the hole that I just reported on (12'O'Clock hole), and report the positions of the rest of the holes with a .0005 tolerance?

Thanks so much...I prefer to use legacy...

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kingsld1 over 2 years ago

Also, the lower frame should only have 1 datum. As written, the FCF is basically just repeating itself, with a tighter tolerance on the lower frame.
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kingsld1 over 2 years ago

Also, the lower frame should only have 1 datum. As written, the FCF is basically just repeating itself, with a tighter tolerance on the lower frame.
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Henniger123 over 2 years ago in reply to kingsld1

Thank you, I was wondering why there are two tolerances at all when a and b are the same
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NinjaBadger over 2 years ago in reply to kingsld1

That's not correct.

The upper segment controls the orientation and location of the considered features with respect to the datums.

The lower segment is only controlling the orientation of the considered features with respect to the datums (and each other)
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kingsld1 over 2 years ago in reply to kingsld1

Respectfully disagree. In my 40 plus years of GD&T, I've never seen a composite position callout that repeated all of the datums in the lower frame. If the upper and lower DRF's are exactly the same, then how does the pattern float? The lower frame always drops at least the last Datum from the upper frame.
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Mike Rivard over 2 years ago in reply to kingsld1

Yes you're right, you usually lose the end datum on a composite
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Neil Challinor over 2 years ago in reply to kingsld1

NinjaBadger is correct, it is perfectly valid for the lower segment's DRF to contain all three datums, it's just the way each segment behaves that changes. There is an example in ASME Y14.5 2018 - fig 10-43 (page 222)
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