Break sharp edge within a surface profile zone...

[ModulusCT]

Hi guys... Please take a look at the picture I've included... Notice the pointed portion at the bottom of the part in the picture. It represents an edge. Points PC to PD are controlled by profile of a surface and one surface therein is further controlled by an angulary tolerance.

The designer wants to indicate that the sharp edge can be broken, but only to R.002 MAX... The radius isn't actually modeled into the part however. My initial thought is that this breakage should be indicated with a flag note. My team lead says that GD&T convention allows a nonbasic dimension like the one in the image and tells me that it therefore falls outside of the control of the profile tolerance. I'm not sure how this can be true. The point to be broken (or maybe not broken) lies within the tolerance zone for the profile gtol, so how can it be considered independently? I'm mainly interested in the standards interpretation of this... but any ideas would be welcome. We're using 14.5-2009. Thanks.



I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!

 

[randy64]

Very eager to people's response to this. All of our drawings fall under a spec that says all undefined corners are to get a particular breakedge. Many times I have used Profile along surfaces that include an undefined corner.

One possible answer is that as long as the breakedge (radius, chamfer, whatever) has a tolerance that is tighter than the Profile it would be okay. Kind of a refinement.

That's all I got...

 

[Belanger]

My team lead says that GD&T convention allows a nonbasic dimension like the one in the image...

He is correct on that point. The radius is not defining the true profile, but adding a refinement to the profile's requirement.

...and tells me that it therefore falls outside of the control of the profile tolerance.

He is not correct about this.
Every tolerance on a print must be satisfied. The .002 radius still must operate within the profile tolerance of .003, which still applies from points PC to PD.

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

 

[CheckerHater]

Agree with Belanger.

The entire profile falls within stated tolerance zone, corner could be sharp, or rounded but no more that stated radius.

Kinda like this:

 

[ModulusCT]

Ahh yes, of course... Thanks guys, that was a perfect explanation and I see the obvious logic in it now. Thank you.

I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!