"Dan Caster" wrote in message
m...
I looked in all my reference books and could only find data in the
Machinery Handbook on the size of drilled holes. Nothing on how
straight drilled hole can be expectd to be on a routine basis. And
obviously nothing on how straight a drilled hole can be expected to be
when done by a skilled machinest. Does anyone have some data on this?
---snip---

I depends on how the hole is started. If you are dead-on into a punched
mark, and you retract frequently at the start, you should end up within
..001" when finished. If you are starting to drill with a perfect drill, you
may get the same result. Most drills will wobble before penetrating that
first thousandth and that is where you get your error. Your best practice is
to locate the part under the chuck exactly where you want it, then start the
hole with a centerdrill and change to the finish drill after breaking the
surface.

Wayne