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James Waldby James Waldby is offline
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Default Drill bit tolerances

On Fri, 02 Oct 2009 20:41:04 -0700, dcaster@krl... wrote:
On Oct 3, 2:17Â*am, "Michael Koblic" wrote:
What is the expected tolerance of drill bits? I have a set of
fractional, letter and number drills. No.12 to 15 (including 3/16")
seem to produce the same size hole.

....
Have you measured the diameter of the drill bits? I could not find
tolerances on drill sizes, but drill blanks are the nominal size plus
nothing minus .0003 inches for blanks up to half inch. I would expect
drills to have about the same tolerances.


Also, are you using a mill-drill, a drill-press, or a
hand-held drill motor? And what is the material being
drilled, ie, wood, aluminum, steel? Clamped or hand-held?

If using a drill press or better and drilling into steel
or aluminum, I would regard it as an unusual problem -- with
the press, the bit, the material, or the work-holding -- if
I drilled a hole with a #13 bit (0.1850") and was then able
to push a #12 bit (0.1890") through the hole without cutting
at least a little more metal.

--
jiw