Slot / snap-ring dimension

[Kedu]

ASME Y14.5-2009
If a slot (groove) width is dimensioned with a direct toleranced dimension (10 mm ± 1) and one side of such said slot is profiled (located) from a datum reference frame (profile xxx |A|B|C|), does the xxx value for the profile should be smaller than 2mm (total size for the width of the slot)?

Note: I know I can use position to locate the middle plane of the slot (and not locate its one side with profile from the DRF), but into the slot is inserted a snap-ring which is biased against one of its side therefore functionally driven.
Functionally the snap-ring biased groove could be within 5mm from the DRF (location of one side of the groove-width of the slot) and the groove/ slot could only be within 2mm total tolerance.
Any issue with this approach? Is it valid within Y14.5?

I am asking in the light of paragraph 8.2:
“Where used as a refinement of a size tolerance created by toleranced dimensions, the profile tolerance must becontained within the size limits.”

 

[pmarc]

I don't see a reason why the profile tolerance value could not be larger than the tolerance for the width of the slot. This is not the application where profile tolerance should be considered a refinement of a size tolerance.

 

[greenimi]

pmarc,

Are you thinking about fig 7-41 from 2018?
X and Y points from 4-34 (2009) have been moved down (and became R and S in 2018) and the width 20±0.2 has been added. (per the new figure we have 0.5 versus 0.4).

Am I correct to say that some portion of 0.5 profile is unusable? (same kind of unusable portion of the tolerance zone seen in 11-21/ 2018, sort of...)
I mean the unusable portion of the profile tolerance zone (0.5) is between point R and the end of the 20±0.2 feature of size (or between point S and also the end of the 20±0.2 feature of size for the right side of the part)

Does "my unusable theory" holds any water?

Thank you pmarc

 

[pmarc]

greenimi,

I wasn't actually thinking about any figure from Y14.5, but fig. 7-41 is good example.

I wouldn't say that the profile of 0.5 is unusable in the areas you indicated, though. For example, I don't see why at the vicinity of point R the contour couldn't be at its MMB, and at the vicinity of point S the contour couldn't be at its LMB.

What you are probably thinking about is that the contour in these areas can't have the form error larger than 0.4 (+/-0.2) because this would be in conflict with Rule #1. Am I correct?

 

[greenimi]

What you are probably thinking about is that the contour in these areas can't have the form error larger than 0.4 (+/-0.2) because this would be in conflict with Rule #1. Am I correct?

Yes. You are correct.

The form error for the outside contour (limited to the common area of 20±0.2) is restricted by the 0.4 tolerance and not by the 0.5 (shown in the profile), hence I said the unusable...

In the close vicinity of points R and S (and a little bit above of R and above of S) the form error is controlled by the profile (within 0.5) and also by the size tolerance (0.4)--indirectly thru rule#1, as you said-- so I concluded that some of the tolerance zone offered by profile (which is more generous) is unusable.

Looks like the committee intentionally drop the points for the profile in between points a little bit lower. (X and Y in 2009 were higher, relatively speaking to the shown drawing)

 

[pmarc]

I am not so sure that everything they did with the figures in the 2018 edition was really intentional, but in case of fig. 7-41 even if it wasn't, it will not harm anyone.

 

[Kedu]

Thank you very much. I appreciate your input.