Geometrically controlled datums (?)

[Wuzhee]

What is the difference between left and right Datum callout?
They mean the same thing or not? I read somewhere they are different but that source failed to clarify.

 

[Burunduk]

Same.
Choose per convenience.

Doing it like shown on the right may be convenient to the reader getting all the information about that feature in one place. If it was a large feature with a lot going on around it, it could be significant.
The way it's shown on the left may be useful when you are short on space.

 

[Wuzhee]

Thanks. So as I thought. Gave me a few days of thinking why they are different according to some people. One of our gageroom technicians also didn't understand the right side callout.

 

[greenimi]

One side COULD be machine readable and the other not. (both of them are human readable and interpretable).
Just saying...

 

[3DDave]

Ah, for the more direct and compact 1982 version. No toilet plunger, no extra decorations. Just the requirement applied directly, not traffic direction signage.

 

[Burunduk]

greenimi,
Both are machine-readable. The placement doesn't affect what is being referred to in the ASME Y14.41 standard as "associativity".