Any fundamental difference here?
Any fundamental difference here?
(OP)
Hi there,
This may seem like a very basic question, but I just want to make sure I'm not missing anything.
Is there any conceptual difference between these two examples? I believe the answer is no, but I'm willing to be corrected.
In general, I'm in the middle of training my group here how/why GD&T is a better approach vs direct tolerancing, but... in this specific example... I can't think of any way these two statements (shown in the attached figure) are different.
Ultimately, if I wanted to give a looser tolerance to the profile (i.e. 0.3 unilateral), and add in a parallelism refinement of 0.2, I believe I could accomplish that same requirement by using a direct tolerance of +0.3 /-0.0 with a parallelism call-out of 0.2. Is that right?
Thanks!
This may seem like a very basic question, but I just want to make sure I'm not missing anything.
Is there any conceptual difference between these two examples? I believe the answer is no, but I'm willing to be corrected.
In general, I'm in the middle of training my group here how/why GD&T is a better approach vs direct tolerancing, but... in this specific example... I can't think of any way these two statements (shown in the attached figure) are different.
Ultimately, if I wanted to give a looser tolerance to the profile (i.e. 0.3 unilateral), and add in a parallelism refinement of 0.2, I believe I could accomplish that same requirement by using a direct tolerance of +0.3 /-0.0 with a parallelism call-out of 0.2. Is that right?
Thanks!





RE: Any fundamental difference here?
RE: Any fundamental difference here?
But in the second picture, there could be a cross-section of 9.9. This is because the profile across the top (which allows a minimum height of 10.0) is measured from datum A. And datum A is the plane established by only the extremeties of the bottom surface. There could be a valley of 0.1 lifting up off the inspection plate, and this might make that particular cross-section as small as 9.9.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Any fundamental difference here?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Any fundamental difference here?
In this case, then, as I've defined the scenario, it seems like the direct toleranced example more correctly accomplishes the design intent.
RE: Any fundamental difference here?
Sure, there are multiple acceptable ways to control any given set of features, but it's fun finding the "Best" way of doing things, and that means arming one's self with the best possible understanding of the rules. The rules ARE sufficiently exact. So, the game for me is both seeing for myself where the wiggle room is, and also figuring out how I can explain things to my coleagues here (we're not even going to get into the Spanish translation part, which is a whole separate challenge for me).
RE: Any fundamental difference here?
Season
RE: Any fundamental difference here?
Always remember, though, that GD&T is a language and like any other language people may say things in different ways. Sometimes they mean exactly the same thing, but at other times a small nuance will make the statements quite different.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems