Using BOUNDARY on an external FOS

[Belanger]

Something interesting that I just noticed, since I recently came across a real-world situation for it...

The Y14.5 standard goes into detail about how to use a position tolerance on a noncircular feature of size. See paragraph 7.4.5.
What's interesting is that all the verbiage is dealing with internal features, such as slots. But I'm trying to use the BOUNDARY idea on an external feature.
Look at 7.4.5.1 -- it says that if a position tol of a noncircular FOS applies at MMC, then the "following apply." Yet every one of the "following" is an internal FOS!

Was this an oversight, or did they intend for it to never apply to an external FOS? (And I'm not interested in using profile, so paragraph 8.8 doesn't really help.)

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

 

[pmarc]

J-P,
I am staring at fig. 7-34 and really can't see why the boundary approach could not be used if the elongated features were external and not internal.

Very interesting observation, by the way.

 

[Belanger]

I agree that it can be done, it's just weird that they keep saying "internal" throughout that explanation. Oh well... extension of principles, right?

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

 

[fsincox]

JP,
You won't have to sell me on it! They have to [ul]
[li][/li]
[/ul]give us something to work with
Frank