Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old October 3rd 09, 02:17 AM posted to rec.crafts.metalworking
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Default Drill bit tolerances

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.

--
Michael Koblic
Campbell River, BC



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Old October 3rd 09, 03:32 AM posted to rec.crafts.metalworking
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Default Drill bit tolerances

mattathayde had written this in response to
http://rittercnc.com/metalworking/Dr...es-201627-.htm :


-------------------------------------
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.



what are you measuring with, 12-15 range .18-.189, also do you have runout
on
your press, how fresh are the bits, etc. your dealing with such small
differences that it will be very hard to get a good read unless you have
very
high quality measuring devices.

-matt


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Old October 3rd 09, 04:32 AM posted to rec.crafts.metalworking
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Default Drill bit tolerances

mattathayde wrote:
mattathayde had written this in response to
http://rittercnc.com/metalworking/Dr...es-201627-.htm :


-------------------------------------
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.



what are you measuring with, 12-15 range .18-.189, also do you have runout
on
your press, how fresh are the bits, etc. your dealing with such small
differences that it will be very hard to get a good read unless you have
very
high quality measuring devices.

-matt


##-----------------------------------------------##
Delivered via http://www.rittercnc.com/
Metalworking Forums
Web and RSS access to your favorite newsgroup -
rec.crafts.metalworking - 175567 messages and counting!
##-----------------------------------------------##


Any bit not sharpened properly--especially one with the point not
centered will drill oversize..
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Old October 3rd 09, 04:41 AM posted to rec.crafts.metalworking
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Default Drill bit tolerances

On Oct 3, 2:17*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.

--
Michael Koblic
Campbell River, BC


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.

Dan
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Old October 3rd 09, 05:50 AM posted to rec.crafts.metalworking
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Default Drill bit tolerances

On 2009-10-03, wrote:
On Oct 3, 2:17*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.


Note that it matters where you measure, too. Drill bits taper
very slightly from the cutting end to the shank (to avoid binding in the
hole, I guess). Certainly don't trust a measurement of the shank to
give the size of the hole it will produce.

As has already been mentioned -- it all depends on how well it
has been sharpened. If the angles or lengths of the flutes are
different, the drill will run off-center, and cut with only one flute,
while pivoting on the "center" as defined by the sharpening, not the
center-line of the bit itself.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---


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Old October 3rd 09, 06:25 AM posted to rec.crafts.metalworking
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Default Drill bit tolerances

On Fri, 02 Oct 2009 20:41:04 -0700, [email protected] wrote:
On Oct 3, 2:17*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
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Old October 3rd 09, 09:40 PM posted to rec.crafts.metalworking
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Default Drill bit tolerances

On Oct 2, 6:17*pm, "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.


I've used the shank of drill bits as gages; they measure within .001"
of
the marked size.

As for the holes, the #12 makes a hole bigger than #13 and smaller
than
#11 (i.e. look at the gap between sizes), unless it's dirty/bent/dull.
Fractional drills, some of 'em, have been off by .005" recently, but
they
might have been made-for-WallyWorld.

People who need real precision don't use twist drills, of course, for
the final dimensions.


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