【转帖】e with metric tolerance

yang686526

"e" with metric tolerance
i am looking for an explanation of the use of the letter e in a circle following a metric tolerance (h6) on a german drawing
check out our whitepaper library.
revision?
in the military/defense world we put this symbol on our drawings to indicate what the changes were on each revision.
here is an example of a milspec bolt
it does not appear to be a rev
drbauer
circle(e) in iso signifies the "envelope principle" which suspends the iso "independency principle" for measurement of size and form and invokes conditions equivalent to the asme "taylor principle, rule #1" commonly known as "perfect form @ mmc".
paul