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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.

Drill bit tolerances



 
 
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  #1  
Old October 3rd 09, 03:17 AM posted to rec.crafts.metalworking
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Posts: 621
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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  #2  
Old October 3rd 09, 04:32 AM posted to rec.crafts.metalworking
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Posts: 6
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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  #3  
Old October 3rd 09, 05:32 AM posted to rec.crafts.metalworking
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Posts: 88
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


##-----------------------------------------------##
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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..
  #4  
Old October 3rd 09, 05:41 AM posted to rec.crafts.metalworking
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Posts: 3,073
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
  #6  
Old October 3rd 09, 07:25 AM posted to rec.crafts.metalworking
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Posts: 271
Default Drill bit tolerances

On Fri, 02 Oct 2009 20:41:04 -0700, dcaster@krl... 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
  #7  
Old October 3rd 09, 10:40 PM posted to rec.crafts.metalworking
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Posts: 1,184
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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