Fig 6-19 - ASME 1994 and orientation (profile versus position) 2

[aniiben]

Does the profile in Fig 6-19 / 1994 (ASME) controls orientation or this job is reserved for the position?

 

[drawoh]

aniiben,

The outline cannot be rotated sufficiently to extend through the LMC and MMC outlines. That is an orientation control.

--
JHG

 

[powerhound]

Profile tolerance controls the perpendicularity of the walls to A. I might agree with drawoh that the boundary created by the position tolerance will probably restrict the orientation to B and C before the profile tolerance IF the feature is at it's MMC size; however, at LMC it will be a close call to figure out which boundary restricts orientation to B and C first (inner or outer.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[greenimi]

Does anyone know/guess why in 2009 revision datum feature A has been removed from the profile? I don't.
Or I am not sure why.

 

[powerhound]

Probably because the inner boundary is already oriented to A via the position callout. The walls can be in any location and orientation within the profile tolerance zone and the inner boundary cannot be violated. I don't think this is an incorrect callout. It's definitely different from the 1994 figure though.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[pylfrm]

aniiben,

I am curious. What lead you to ask this question?


pylfrm

 

[pmarc]

I am curious. What lead you to ask this question?

Maybe it is the wording of associated paragraph in the standard (6.5.5.1):
"In this example [fig. 6-19], the basic dimensions and the profile tolerance establish a tolerance zone to control the shape and size of the feature."

Because of presence of A in the profile callout, that statement seems incomplete at best.

By removing A from the profile callout in the 2009 standard, this problem was solved.

 

[Belanger]

However, pmarc, having datum A in the profile tolerance at least allowed the two geometric tolerances to be measured on the same primary plane. Perhaps that made it easer for gaging; just drop the part onto a table, and it would be a simple matter to engage B and C when needed for the position measurement.
But I agree that the actual relationship to datum A is controlled by position, and you make a good point about the picture now matching the text description.

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

 

[SeasonLee]

greenimi

With the presence of A in the profile callout, it will not only control the shape and size geometric characteristics but also the orientation, the table below is a good reference. (quote from Alex's Advanced Concepts of GD&T page 22-9)

Thanks pmarc lead me to look at this table, you catched the point shape and size.

 

[greenimi]

Since some answers were addressed directly to me (even I am not the one who asked the original question) I would say that having datum feature A in the profile is a mistake in the standard (rectified by the 2009 revision). In the court of law only the text (and yes, not the pictures) counts and considered in a legal argument. Pictures only help visualize the concept.
That is my opinion based on pmarc's referenced paragraph from 1994.