Can Flatness be a refinement of Profile?

[randy64]

I will attempt to describe my situation in words:

The part is basically a tin can shape (but thicker than tin) with a flange at the top rim. I want to control the flange area with Profile of .01", but engineer wants the bottom of the flange to be held Flat within .002". For the profile, I will call it out between points A and B. Within A to B is the bottom of the flange that needs to be Flat.

Is this a correct thing to do? Can something be called out as Flat within an area that is being Profiled, as long as the Flatness is held tighter?

Thanks

 

[powerhound]

Flatness can be a refinement of profile as long as the surface being controlled is nominally flat.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

 

[CheckerHater]

Is Profile control using datum(s)?

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[randy64]

Yes CH, Profile is using datums.

 

[CheckerHater]

OK.

It just was my thought, that if Profile controls just a single nominally flat feature without reference to datums, then profile essentially is no different from flatness.
In this case tighter flatness requirement will simply override it.

Now, if profile is controlling orientation / location, etc., flatness is legitimate refinement and I join powerhound with "yes".



"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[JNieman]

Without knowing more about your part, this suggestion may be way off mark, however:

Would Perpendicularity meet both of your requirements in a more elegant manner, or would a tolerance zone perpendicular to the relevant datums not be appropriate?

 

[randy64]

Here's the situation, just so you know what I'm talking about. Obviously not showing dimensions, etc., just showing the areas and shape of part.

 

[ewh]

Looks legit to me.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[CheckerHater]

Even more "yes" than before

Randy,

Your sketch sure looks like a "tin can" to me

 

[JNieman]

Looks clear and practical to me. That is not what I had in mind when I read "flange" though. I was thinking "bolt flange" more than a feature like that! Now that I see the part, yea, that looks clear to me, assuming Datums C and D are logical.