GD&T Help

[ccarpent]

I would like to get comments on the attached sketch.

1. Are the GD&T tolerances done correctly?
2. Does the parallel .005 to B do anything or could it be left out with no change to the tolerance?

Any help/suggestions will be greatly appreciated.

Thanks,
Chuck

 

[pmarc]

Can't open the attachment. Try to reload.

 

[ccarpent]

I must be doing something wrong. I can,t upload the file. I'll worl on it.
Chuck

 

[ccarpent]

OK I got it.
Chuck

 

[powerhound]

The thing that is wrong with this is where you are trying to specify and control datum C. This is not a correct application of perp or parallelism given teh scenario. I think it would be better if you controlled the flat using profile of a surface to A and B and giving a basic dimension from the centerline to the flat. Now you can attach a datum identifier to teh feature control frame and call the flat datum C. This is, of course not the only way to do it, but it is GD&T legal. Others will have other suggestions I'm sure.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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[ccarpent]

Powerhound,

I agree. I could also use a positional tolerance. I was trying to avoid giving up the .50 +/-.01 tolerance.

Thanks,
Chuck

 

[pmarc]

Actually, assuming that the datum features were chosen according to the function of the part, I do not see much more options than the one described by powerhound, with one remark however:

The tolerance for a distance of flat surface from axis B is .02 while both orientation tolerances are .005, so (assuming there is a reason for it) it would be logical to apply composite profile tolerance to that flat surface and attach the datum identifier C to composite FCF. Both segments would refer to A|B datums (which may look weird, but IMO is absolutely legal).

Additional 2 comments:
1. There is no size dimension and GD&T applied to the center hole with the flat.
2. If you are working according to ASME Y14.5 std., positional tolerance is not allowed for planar surfaces - profile is the one you should choose. In ISO 1101 world you can use position.

 

[ccarpent]

Thanks for the help. It looks like profile of a surface is the best choice.

Thank you,
Chuck