02-24-2014, 05:59 PM
JASmith Wrote: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.
Well, as a machinist, if I got that drawing on the floor I would use the decimal tolerance call-outs (+0.0004) , unless there was a spot where they were called out in actual fraction form (1/8, 1/4, 1/2) for which I would apply the +-0.001. Don't know if that helps or not.
Also, I'm not saying that the reamers are or are not right or wrong, I'm just saying that the print is right.