Held Flat?

[[Ri...]]

I have a part that a note on the print states:
All features to be measured when Datum A is "held" flat.

What is the definition of "held"?

There is a Flatness for Datum A.
Is "held" obtained when the Flatness is in tolerance or does "held" imply restrained?

[[Ia...]]

I'd guess that it is the unscientific way to say constrained. I've never heard that jargon before though, would probably reach out to customer/design engineer.

[[Ow...]]

In one company I seen a few prints that require a datum feature to be tightened/secured in four places against an angle plate.
The angle plate basically simulated the mating part that the part being measured would eventually be bolted to. It was also machined while being secured the same way and when unbolted, it would flex significantly and wouldn't check good unless secured back the same way.
In that case, instead of adding cost to make a casting that wouldn't distort (after machining) or add process operations , manufacturing/engineering were satisfied of it's structural integrity as long as it checked good when assembled.

[[Ri...]]

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Constrained and restrained have different meanings.

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Held

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[[Ch...]]

Not that uncommon. Some things just can't be measured in a free state. Think of something like a body panel for a car. How you fixture/clamp the part will have direct impact on your CMM measurements. In cases like this, you would 'hold' the part in the same way it is 'held' on the assembly line.

I kinda feel like saying. "It depends on what the meaning of the word 'is' is"

[[Ia...]]

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I'd like to very formally apologize for my barbaric understanding of the English language. Thank you for pointing that out in a non-condescending way.

But,

When you say "There is a Flatness for Datum A", don't you really mean datum feature A? Did you know that datum vs datum feature have different meanings? I can google it for you if you'd like.

[[No...]]

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Possibly the latter. As Chad already said, some parts can't be measured in a free state. For us (plastic parts) it's everyday routine to force parts to a quasi-assembled state, which is often also stated on the print.

As to the usage of the term "held" I can't say much, being a native German. But I know we have a semi-automatic translation function in our PLM system, with which the designer can create translations of numerous technical terms on the print. The results are always good for a laugh.

[[Er...]]

For our sheet metal it is common for 3 A datum points (A1, A2, A3) to be called out as "held." Held, constrained, or a half dozen other wordings meaning the same idea. We just have a modular fixture and place three magnets opposite those points. Then flatness is measured.

It can seem really sloppy, and truthfully it is compared to finely machined parts.

The tolerances, accuracy, and repeatability are different from stampings to something that is ground and polished. Some stampings have variation of 1mm or more. Some machined parts are more a test of me and the CMM.