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A few GD&T questions

A few GD&T questions

A few GD&T questions

Hoping I can get some help on some questions that I can’t quite find a clear answer for in either the ASME Y14.5 standard or already on this site (not the most experienced with GD&T yet).

Question 1), cylindricity- I have an application where we are welding up a bearing housing and machining afterwards. With the residual stresses in the bearing housing from the welding process, the bearing housings can slightly go out of round during the machining process. I already know that per the standard, the cylindricity tolerance must be less than the dimension tolerance. From previous application experience I know I need to maintain a tighter than normal control on the average size of the bearing bore. On the other hand, the bearing itself can handle a little more “out of roundness” than what my dimensional tolerance allows per the standard. The only thing I can find in the standard that could possibly allow my cylindricity tolerance to exceed the dimension tolerance is the “average diameter” as described in paragraph 5.5.3 of the 2009 standard. I’ve seen on another thread here that one guy used “perfect form @ MMC not required” instead (assuming with a cylindricity tolerance). Is my “housing” in the attached example legit? I don’t believe I would have to specify the free state condition in the feature control frame??

Question 2), true positon of a keyway-I’ve seen a few examples of locating a keyway on a shaft in this forum, all differ by their particular application and some with controversy. Can someone confirm that I’ve properly used GD&T to locate the keyway position in the “shaft” example? I’m only concerned about the keyway being centered on the shaft on the datum C portion, axial location is not critical.

Question 3), locating of splines with GD&T-I also wanted to apply some GD&T to some internal splines in the shaft and relate it to the bearing seats (datum’s A & B) that this shaft is ultimately located by and spins on. This just to make sure that the mating splined output shaft of hydraulic motor will install into the piloted bearing housing with this splined shaft in. I was thinking of just using concentricity to locate the axis of the splines relative to the bearing seat axis and using the ANSI B92.1 callout for the machinist to refer to for the technical information on the splines. Does this look legit as well?

I appreciate everyone’s input. Thanks

RE: A few GD&T questions


1) Looks fine to me.

2) Looks fine to me.

3) Concentricity tolerances can only be applied to surfaces of revolution, so your example with the spline is not valid. You probably want a position tolerance instead. Depending on the details of ANSI B92.1, you might be able to apply the tolerance to the entire feature at MMC instead of to the pitch diameter RFS.


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