y14 question

[jjslife]

got a question for ya'll.
i just seen on a drawing a feature having a true position call out rel to datum -A- with MMC and datum -B- with MMC the feature was a hole and the datums were surfaces, my question is how does a surface get MMC ????

 

[pmarc]

Y14.5-2009 gives some examples of (M) modifier applied to secondary datum features which are surfaces (see figs. 4-29, 4-30, 4-31) so theoretically it is possible and legal, however having two planar datum features applied at MMB looks at least suspicious. Are you able to show any sketch of this?

 

[drstrole]

As pmarc indicated this is legal in certain cases in the 2009 standard for surfaces, it is not legal in the 1994 standard. A sketch would help the discussion.

Drstrole
GDTP - Senior Level