Hello, Is there any scenario whe

[isthispraveen]

Hello,

Is there any scenario where we have to use the cylindrical surface as the datum and not its axis?
I mean to ask if putting the datum on a cylindrical surface is wrong.

 

[cr7]

Hi,
I'm unsure about this in ASME, but in ISO it could be used for parallelism of the opposite side. Sorry, I don't have anything to share at the moment, except if you check the link -> Link and try to imagine the parallelism (to bottom datum) instead of straighness shown.
A word of caution, please don't rush to throw that on a drawing if measured with CMM. It would require probe system with multiple cylinder probes which is tedious to set-up and cylinder probes usually adds some measurement uncertainty.