Refining a profile tolerance with an inch/inch type spec?
Refining a profile tolerance with an inch/inch type spec?
(OP)
I believe it has been discussed before here:
Can a profile tolerance be refined with an inch/inch type specification? or a sqin per sqin specification?
Like straightness or flatness does.
Can a profile tolerance be refined with an inch/inch type specification? or a sqin per sqin specification?
Like straightness or flatness does.





RE: Refining a profile tolerance with an inch/inch type spec?
http://www.tec-ease.com/gdt-tips-view.php?q=112
Powerhound, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
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RE: Refining a profile tolerance with an inch/inch type spec?
Thank you and Don!
RE: Refining a profile tolerance with an inch/inch type spec?
2. I am curious why flatness per unit area callout was not used instead of lower segment of profile FCF? Does 8.3.2.2 really say anything about profile per unit area application?
RE: Refining a profile tolerance with an inch/inch type spec?
The note in 8.3.2.2 does indeed mention "per unit length" but not you've got me thinking that "per unit area" makes more sense because profile of a surface is applied to a 2-D or 3-D surface. So one linear dimension only seems incomplete?
In the OP I think Frank was referring to this thread from a while ago:
http://eng-tips.com/viewthread.cfm?qid=325577
If I recall, the issue was for profile applied to a contoured surface, where it might not always be clear if the given area dimensions conform to the curve or are the flat-only dimensions of the area. Obviously that's not an issue in the Tec-Ease tip.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Refining a profile tolerance with an inch/inch type spec?
Yes, that was it. Don's example does mention non-flat surfaces at the end, there too.
RE: Refining a profile tolerance with an inch/inch type spec?
Are you saying that flatness per unit area callout as the 2nd FCF would not be equal to what the tip shows? (Of course we are talking about controlling geometry of nominally flat surface here).
RE: Refining a profile tolerance with an inch/inch type spec?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com
RE: Refining a profile tolerance with an inch/inch type spec?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Refining a profile tolerance with an inch/inch type spec?
That is totally true what you are saying.
However in the tip there is only one datum involved, so resequencing is not really an issue.
Let's imagine the tip with slight modification. The upper surface being controlled by 3-segment composite profile FCF:
|prof.|0.6|A|
| |0.3|A|
| |0.1|
And now, let's switch it to 3 separate FCF's:
|prof.|0.6|A|
|paral.|0.3|A|
|flatn.|0.1|
I guess we agree that these are equivalent callouts. So how do you think, which option will be clearer for an average GD&T user?
I wonder how many folks would grasp the difference between 1st and 2nd segment in the composite profile FCF.
RE: Refining a profile tolerance with an inch/inch type spec?
Out here, we are going to use the three tier composite only when no other control will do, just do to its lack of a strong definition in earlier standards (we still reference 1982). I was a strong advocate of the addition of a definition for the restatement of datums in a composite tolerance and saw no reason to make it the same as 2 separate statements. I am very pleased by the way this issue did turn out in the standard. It just adds more tools to our tool box. It is one of the few things that did turn out like I thought it should! :)
RE: Refining a profile tolerance with an inch/inch type spec?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Refining a profile tolerance with an inch/inch type spec?
Peter Truitt
Minnesota
RE: Refining a profile tolerance with an inch/inch type spec?
I reviewed the previous thread again, but I don't see why you would consider these 3-D zones; the zone boundaries would be offset from whatever the basic geometries are. For example, pictue an Eggo Waffle with an all-over profile control. The tolerance zone boundaries would be the expanded & contracted offsets from the nominal surfaces. Thus, I don't see any relevance to the spherical versus cubic tolerance zone, except as an abstract consideration. I seem to be missing the point of it?
Jim Sykes, P.Eng, GDTP-S
Profile Services www.profileservices.ca
TecEase, Inc. www.tec-ease.com
RE: Refining a profile tolerance with an inch/inch type spec?
Peter Truitt
Minnesota
RE: Refining a profile tolerance with an inch/inch type spec?
Any waffle would do, it doen't have to be eggo. :)