Concentricity Gage

[engiNERD77]

Hey guys-I am making some revisions to a concentricity gage. The features being checked are a threaded hole to a bore with a tolerance of .005. The bore dia. is .497-.503 and the gage dia. for that same bore is .483-.484. This struck me as very sloppy. I would think you would want the gage dia. to be as close to the min. dimension as possible. My question is whether I am correct in my thinking? Thinking about it further ...if the bore is at max dimension that allows it to be out of concentric by like .003 and the gage still saying it is ok. So my other question is whether I am thinking about this correctly at all? Thanks in advance.

 

[JNieman]

You didn't specify the form or class of thread - there may be tolerance to that minor diameter being accounted for.

Speaking of: what kind of threaded hole are you checking to a positional tolerance of .005 and how are you checking that? Are you checking the minor diameter or the pitch diameter? If pitch: how? I guess a better idea/picture of the part might make it obvious to me.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[engiNERD77]

The threaded hole is a 21/32-6 RHS 60° modified stub acme and the callout is for that to be concentric within .005 to the fore mentioned bore. Basically what we are using is an alignment gage with a threaded section on it. It just seems the existing gage with the dimensions I mentioned earlier would pass a bad part.

 

[engiNERD77]

Here is a rough idea of what I am looking at. I hope this clarifies. Any thoughts?

 

[Belanger]

Since the datum being referenced doesn't have an "M" after it, then you can't really do a fixed-size gage plug for the bore. You have to lock onto datum axis A regardless of size (expanding gage).

Also, if the print is following the ASME Y14.5 style of tolerancing, then the symbol should be position rather than concentricity (and have a diameter symbol before the .005).

But the bottom line for your question is yes, the current setup is too sloppy. If they had the "M" after the datum A reference, then you could use a fixed gage, but even there it should be pretty darn close to the .497. Using .484 is way under the smallest bore size.

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

 

[engiNERD77]

Thanks B ...that seems to make sense to me.