Does the ISO allow for Radial Datums Features?

[fsincox]

Does anyone know specifically if the ISO allows for datum features to be used on a partial diameter feature (radii)?

 

[Belanger]

Don't know for sure, but I'm looking at ISO 5459 and I don't see any provision for such a thing.

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

http://www.gdtseminars.com

 

[pmarc]

J-P,
Which version do you have? 1981 or 2011?

 

[Belanger]

By golly ... it's 1981.

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

http://www.gdtseminars.com

 

[fsincox]

Thanks, guys
thread1103-314002
The part in that thread sure seems like an example of where you might want to use a partial dia as a primary datum at RFB.
Frank

 

[pmarc]

Frank, of course it is possible that the radial feature is a good one for serving as a primary datum feature, but for me there is not enough info to be sure about this, we do not see or know anything about mating conditions of the part.

I will try to organize newest edition of ISO 5459 (2011) which deals with datuming, but to be honest I do not expect to find anything clearly legitimizing usage of such kind of features as datum features. Let's hope I am mistaken.

On the other hand - as you well know - ISO GPS standards philosophy is to show rather generic than specic examples of geometrical tolerancing, so lack of clear indication of a concept does not mean that the concept must be considered prohibited right away.

 

[fsincox]

pmarc,
Thanks, I agree we do not know that is why I started a separate thread not to confuse his other issues and allow myself the flexabliity to "say" how it mounts to make this point. I do feel it looks like the part he shows will mate to a shaft with the screws shown. The shaft will align the part when drawn tight with the screws forcing an alignment of the radius to align along the shaft diameter.
I wanted the freedom to dicuss this radius as a datum thing.
Frank