> -----Original Message----- > From: piclist-bounces@mit.edu On Behalf Of R. I. Nelson > Sent: Thursday, December 01, 2005 1:28 PM > > every drawing most of the stuff I did was + or - 0.0005". but we > still tried and usually achieved 0 tolerance. our measuring tools were > checked daily and we had gauge blocks to double check them. To be correct you should say that you could not measure the deviations with the equipment you used. No measuring instrument or gauge block has zero error. Even the NIST Length Scale Interferometer has an uncertainty in it's measurement, it is incredibly small but there. Paul -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist