"Dan Caster" wrote in message
m...
Thanks Sy,

This is exactly what I was looking for and I have now bookmarked the
starting page for the design book. Lots of data there. From what
others have said it looks as if one can be within about half or one
third of these tolerances if one is very careful and has some good
luck.

This should be very helpful to a lot of us recreational metalworkers.

Mil specs and handbooks often have a lot of valuable information.
Finding the mil spec can be a problem.

Thanks again,
Dan
(Sy) wrote in message

Hello Dan,
There is a military standard for drill hole size tolerances. It is
AND10387. See http://www.bjg-design.com/designbook/holest.htm
Also look at http://www.bjg-design.com/designbook/drilld.htm for drift
tolerance for drill holes. Also look up
http://www.bjg-design.com/designbook/formhsiz.htm for positional
tolerances.
Sy

Of all the territory covered here I didnt' notice anyone mention to use a
new drill bit from a reputable manufacturer (save the resharps for rough
work) and use a screw-machine length if possible. Maybe it goes without
saying.

Also I didn't see mentioned classic drill jigs with precisely located
hardened guide bushings. That's got to count for a lot when using skinny
bits or when using a drill press instead of a mill.

I vaguely recall a Teenut thread on the topic of sharpening drill bits, and
spent a minute Googl'ing without success. Gist was, sharpening is fine
(though its economics are questionable for small bits), but even with skill
and a good quality grinder it's impossible to get drills to drill to new
spec with regard either to diameter or straightness.

Bob