"Jim Wilkins" on Thu, 13 Jun 2013 10:16:31
-0400 typed in rec.crafts.metalworking the following:

It may be an accumulation of rounding errors. I've had to manually
reconstruct the intended location of features dimensioned as two-place
decimals obviously converted from fractions, 0.62" for instance, and
make sure the sum of dimensions equalled the (ref) length of the part.
That was trial-and-error detective work.

We was told that some drawings will have .13 (etc) where it is
actually .125 "but everyone knows that" and the dimension precision is
held to 0.00 because it is cheaper than 0.000.

A friend at Saco did that for the 50 cal machine gun that John
Browning originally dimensioned to 1/128".

Yikes.

It's helped to learn the fractional and metric conversions, so I
recognize that the 0.434" I measured on an old South Bend part the
other day was 7/16" minus a production tolerance, or 0.that 470" means
12mm.

12mm =.472 - they're cheating, again.

--
pyotr filipivich
"With Age comes Wisdom. Although more often, Age travels alone."