Can you apply MMB with orientation tolerances?

[sendithard]

On the surface it seems in 2009 standard the only explicit usages of MMB is with Position and Profile.

If Datum A is a feature of size cylinder and another cylinder is desired to be parallel to it. I don't see a problem with MMB for datum A.

The idea that with orientation translation doesn't matter is fine b/c the datum shift also allows some rotation which could help with orientation. There are no examples in the standard though.

 

[Burunduk]

Per the 2009 standard,
You can't use material boundary modifiers (MMB/LMB) for runout, symmetry, and concentricity. For the rest of datum referencing controls (orientation tolerances, position, and profile) it is allowed.

 

[Belanger]

It would be OK. A functional gage would be two fixed-size pins that can translate toward/away from each other, but the parallelism would be validated.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[3DDave]

Yes.

Which modifiers can be used on features and datum references is clearly mentioned in a table that is not part of the standard but is likely sold by committee members as part of training materials.

Almost kidding. This relationship (not tabulated) was included in the decision tree in Appendix E Decision Diagram in the 2009 version. That diagram was removed without comment in the 2018 version.

Anyone knowing the format of the diagram and having an understanding of the basic reasoning in the standard should be able to duplicate it from memory. AFAIK the "test" is just regurgitation of the best choice quiz, so that won't be necessary.

 

[axym]

sendithard,

I agree that Y14.5 does not mention any restrictions on which datum features and modifiers can be used with orientation tolerances, but only provides examples with planar datum features or features of size referenced RMB. I don't see a problem with applying datum features at MMB either - there would be some applications for this.

Let's say that I'm mounting something (say a TV) that attaches to the wall using the back face and 4 clearance holes that bolts go through. I can use the clearance on the mounting holes to adjust the orientation of the TV so that it looks level, and then tighten the bolts. The GD&T drawing for the TV could have a Parallelism tolerance on the top edge, that references datum features on the back face and the 4 mounting holes (at MMB).

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Belanger]

With a little help from the Paint 3D app...

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems