02-24-2014, 05:37 PM
Adam Lilja Wrote:I don't see where you are getting +-.001 from that drawing, unless you're going off the fraction tolerances. Which when you look closely there isn't a single fractional call out. Since they are all decimals wouldn't they be going off the decimal tolerance at the bottom of the sheet which is -0.000 +0.0004. There is the weird jargon at the very top of the page but as far as a print goes, the bottom section would over ride that.
Adam,
Thanks, you are demonstrating the value of polite discourse to get some of these details thrashed out!
After first admitting that I did not earlier do detailed research on the term "fractional tolerance" I did a more thorough review so I could better respond to your comment.
As near as I can tell from the discussions of "fractional tolerance," there is no standard defining them. Most of the discussion refer to fractions of an inch, e. g. "1/4" "i/8", "1/64", etc.
At this point one takes the dangerous step of assuming that the call-out using a decimal means that the drawing actually means +1/1000" to - 1/1000" with the key question being: "What does the use of a decimal in a fractional call-out imply?"
So, one assumes that, absent a discussion of how tolerances are applied by the reamer maker, we take the most liberal interpretation.
Should you or any other fellow (or sister) forum member have insight that would help clarify, please pipe up with a definitive answer.