GD&T bilateral profile - doubling the deviation

[[Ro...]]

Exactly. I agree 100%. That's my argument against reporting profile as a 2x deviation. It only makes sense, somewhat, for bilateral/unilateral, and I think the standard should cover all cases, including unequal distribution. Plus, Min/Max simply gives you more specific information that I find to be the most helpful.

Then there's the realistic and pragmatic side, aside from the theoretical stuff. I'm going to have the machinist's shoot for the mean 99% of the time on unequal tolerances, because that usually gives them the greatest chance to make a good part. The rare exceptions are on things like True Position of 0 with MMC, in which case they need to shoot for the least material condition to have the most amount of bonus tolerance.

[[Ri...]]

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Yeah those True Position with zero tolerance @MMC are tough. It forces you to make your hole/shaft large/small. Hopefully they give you enough size allowance. Then the SQEs come in and wonder why the capability for the hole/shaft is skewed - just point at the DE and let them answer that question.

[[He...]]

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Y14.45 deals with unequal distribution in the same way as equal distribution.

But it is a good thing Calypso will let you switch to two results on profile and profile of a line and it presents it as a +0,009 / -0,001 dimension instead.

ASME Y14.45 9-3.PNG