3121GO, the reason I said 'may be wrong' is because while a 'number' can go in that location and mean something, it doesn't mean what I took the OP wanted it to mean.
Both are showing the same thing. The right one is correct as per current ISO standards (BS and DIN included) but both are suspect as they do not denote Ra or Rz. In such a case the lettering is normally put before the number using the symbol shown on the right to read "Ra 1.6"
I work for a firm where most of the components use Ra but some running surfaces require Rz, I think its mainly to keep the drawings looking tidy that our internal standards dictate we lable both.
The other reason im all for it is that it's 2 characters and I'm all for stamping out every trace of ambiguity - have come across far too many people trusted to read drawings who given the chance will misinterpret everything they can get away with.
Will Walters
Sheffield UK
Designer of machine tools - user of modified screws
"The other reason im all for it is that it's 2 characters and I'm all for stamping out every trace of ambiguity - have come across far too many people trusted to read drawings who given the chance will misinterpret everything they can get away with."
This is what experience brings, sense! I fully agree.
