ISO GPS - Position of Surface to Datum A

[Mech1595]

All,

Below is a grossly oversimplified model, as I can't share the original I received from a customer. Customer print is to ISO GPS.

For Datum Features A2 & A3, they have a position specified with respect to [A]. Is this valid?
I know that position to a surface is valid in ISO, I'm just not sure about the reference to [A], as those features are part of what defines [A].

 

[greenimi]

I think in ISO the A1, A2, A3 are used for datum target points, lines etc. Not sure what is currently shown on your drawing is correct.
ISO5459-2011 could be a good resource for you and for your customer.

Ask THE CUSTOMER what is the DESIGN intent.

 

[Mech1595]

Not sure what is currently shown on your drawing is correct.
ISO5459-2011 could be a good resource for you and for your customer.

Thanks for the reference, I'll see if I can get a copy to review. We primarily work with Y14.5, so ISO prints always cause me some pain.

The odd thing is in another view (top), they do have A1, A2, & A3 defined with circular datum target areas (actual part has thru-holes on those tabs for fasteners), but then show exactly what I have drawn above.

 

[greenimi]

See this discussion

Defining Datum as Section of Surface - Drafting Standards, GD&T & Tolerance Analysis

Hi, First up I'm an ISO guy. I have a shaft and I want it's axis to define my datum A. The caveat is that I only want a section of the surface be used to define the datum - the first 110mm from on end. see this image: So I've got two locations defined already, K and L for another feature. I...

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