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Unilateral Profile Tolerance with Bonus
3

Unilateral Profile Tolerance with Bonus

Unilateral Profile Tolerance with Bonus

(OP)
Curious about the interpretation of the unilateral tolerance zone in the following example. As A departs from MMC, does the bonus tolerance applied to the profile control now allow for removal of material, or is the implied 'outside only' condition preserved, ie. would the implied profile callout at a diameter of 14.8 be |0.5 U 0.1| or |0.5 U 0.5|?

Or perhaps the better question - is this even a valid callout?

RE: Unilateral Profile Tolerance with Bonus

Datum feature A establishes an axis - wouldn't the basic dimension be drawn from the center of A? Well, technically, from the center of the true geometric counterpart of A at 15.2?

RE: Unilateral Profile Tolerance with Bonus

(OP)
Good point. I guess the question about bonus tolerance still applies though.

RE: Unilateral Profile Tolerance with Bonus

Since the feature is not located to datum feature A it's not a valid call out.

Had the dimension been to the datum feature axis it would work as imagined by creating a gage that has a partial 15.2 diameter boundary with a scribe line that is some value, whatever it is supposed to be, from the center of the diameter to where the flat is and another that is 0.1 farther than that. Drop the part in the gage and as long as it can be manipulated so the flat lies between the two lines and is not smaller than 14.8 diameter, it passes.

RE: Unilateral Profile Tolerance with Bonus

If the basic was drawn from the center of datum feature A, then what the callout is establishing is a planar tolerance zone of width 0.1 starting at the noted basic dimension and extending outward. The MMB modifier on datum feature A should do nothing to modify your tolerance value internally or externally. The only purpose of the modifier would be for some added mobility when A departs from MMC size.

For example, let's assume the planar surface is meant to be 13.5 BASIC from the center of A. Let's assume that it measures at 13.7 - it's too far away. As datum feature A departs from MMC, it can translate/rotate within it's true geometric counterpart (of MMC size) until the planar surface is located back in the tolerance zone described above.

RE: Unilateral Profile Tolerance with Bonus

Side note - profile tolerances are always applied RFS. The (M) in conjunction with the datum feature callout is a Material Boundary Modifier which denotes Maximum Material Boundary (MMB) for datum feature A. This allows datum feature shift (the behavior that Jacob described), and is NOT a bonus tolerance - though it might look like one in some cases.

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