On Tue, Jun 25, 2013 at 9:17 AM, Bob Stewart <b...@evoria.net> wrote:
> Hi Hal, > > I had always used 25.4001 or .03937 to do my conversions. So, I looked > online and found the .039370078 and did the reciprocal. It is, indeed very > very close to 25.4. If you google "25.4001 conversion" you can find lots > of tables using that as the conversion factor online. I don't know where > the error came from or why it's quoted so regularly. But, it appears to > be the rounded result of taking the reciprocal of a rounded number. Don't > machinists use this number for conversion? Some years ago in 1959 the inch was re-defined to be exactly 25.4 mm. Before that time the inch was only very close to 24.5 mm But for the last 50+ years 24.5 has been an exact conversion. Likely people who are now 65+ years old where taught something different in school if they were in school befoe 1959 and did not keep up with this. -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.