Fig. 11-29 of Y14.5 standard

[Garland23]

In Fig. 11-29, I'm fine with the idea of profile and position combined. My only question is why they refer to paragraph 7.17?
For each figure in Y14.5, they provide one or more paragraph numbers (in the lower corner of the graphic) that link to the idea being depicted. I'm wondering if this one is an error, because none of the datums are irregular features of size (or FOS of any kind).

 

[3DDave]

I suspect they were grasping for an irregular feature that could be used as a datum feature to show what the MMB would be; it's somewhat unsatisfying for the reason you mention, but it's not an error, just a bit lazy.

 

[axym]

Garland23,

I believe that referencing 7.17 was intentional, because Figure 11-29 is referenced in section 7.17. But I would also question why 7.17 is referenced.

The toleranced feature in 11-29 is an irregular features of size, type (b) as defined in section 3.35.1 (b). But it's not a datum feature, so the material boundary conditions discussed in 7.17 do not apply.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[3DDave]

It seems like tacking "of size" onto every feature regardless of the math standard makes anything a feature of size. A vertex can be contained by an unrelated AME - voila - any vertex is a feature of size.

 

[Belanger]

I'll take a stronger stand than my 2 colleagues here. Since paragraph 7.17 is all about irregular FOS used as a datum feature, it simply doesn't apply to 11-29. Chalk it up to an error.

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

 

[3DDave]

All the figure required was to add a datum feature symbol under the position tolerance feature control frame and boom - it's an irregular (feature with no directly applied tolerances of size) datum feature boundary.

And this is why the next version should just be a picture book. If you can find a matching picture there's no need to think about it.