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Milling 3 flats on drill bits

dator76

Plastic
Joined
Jan 13, 2014
Location
United States
I'm attempting to mill 3 flats on my drill bits I have ER 25 Collets and a hex holder. The collets will not hold the drill bit in center. I need to be able to clamp on the flute part of the drill bit. Do I need to use a different type Collet?
Thanks
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Three flat drill shanks are a delusion,unless you are using them in a loose socket type of holder.........you will find the typical 3 jaw drillchuck cannot hold a 3 flat shank without repeated tightening.........try it yourself if you dont believe me.
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
You can buy drills with the flats installed at the factory. Viking Drill makes very good 3 flat bits.
 

Scottl

Diamond
Joined
Nov 3, 2013
Location
Eastern Massachusetts, USA
Three flat drill shanks are a delusion,unless you are using them in a loose socket type of holder.........you will find the typical 3 jaw drillchuck cannot hold a 3 flat shank without repeated tightening.........try it yourself if you dont believe me.
3 flat drill shanks are meant for portable drills where it's hard to keep perfect alignment and a sudden "catch" can make the bit slip. I wouldn't use them in machines for reasons as you mention.
 

crickets

Hot Rolled
Joined
Jul 3, 2021
I would make a sleeve. Take some round stock, drill and ream for a close sliding fit. Better yet, if the diameter allows, bore it for the same. Then cross drill and tap for the set screws. Put your drill in that sleeve, and then hold that in your collet block using a normal collet, obviously matching OD of the sleeve.

I would probably try to setup for two set screws opposite of each other so they can engage into the flute on the opposite sides, and maybe use brass screws instead of steel ones.
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
I'm attempting to mill 3 flats on my drill bits I have ER 25 Collets and a hex holder. The collets will not hold the drill bit in center. I need to be able to clamp on the flute part of the drill bit. Do I need to use a different type Collet?
Thanks
What machine are you using to mill the flats ?
 

tnmgcarbide

Diamond
Joined
Jul 6, 2004
Location
N. GA- 33.992N , -83.72W usa
i won't re-iterate that a drill-bit is a woodworking tool....
in fear of stating that a man has a bosch mighty midget..but
"The collets will not hold the drill bit in center" is a question .
a collet should grip the shank of a drill..at least as well as a drill-chuck.
if it doesn't, check for burrs, trash that might distort a good fit. or ... your
"drill -bits " or collets are shit , and poorly made.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
ER 25 Collets and a hex holder should hold drills Ok and reasonably good to center holding onto the flutes. The hardness of the drill shanks may be a factor, if over file-check hard a carbide cutter or grinding wheel may be needed.
The thickness times the length may make them bend away from the machining action, for instance a 1/4 " drill shank 1" long will surely try to bend away from most milling or grinding actions and so some kind of out-end support may be needed.
For the amount of time and effort trying the put flats on a jobber set of drills, buying a set already flatted might be better.
One outboard (point end ) support might be a steel block with a hole at the same height as the center of the hex holder, so the out end(point) set in that hole would act like a center and a between-centers operation would exist.
Likely three .020 deep flats would be enough to chuck on the shank with/in a drill chuck.
A little back taper would help hold the altered shank hold in a Drill chuck, .002 per inch getting smalled towards the point.
 
Last edited:

camscan

Titanium
Joined
Sep 5, 2011
Location
Norfolk
i won't re-iterate that a drill-bit is a woodworking tool....
in fear of stating that a man has a bosch mighty midget..but
"The collets will not hold the drill bit in center" is a question .
a collet should grip the shank of a drill..at least as well as a drill-chuck.
if it doesn't, check for burrs, trash that might distort a good fit. or ... your
"drill -bits " or collets are shit , and poorly made.
Drill bits are made to cut many different materials, including steel.
 

camscan

Titanium
Joined
Sep 5, 2011
Location
Norfolk
you can spake what suits your profession. in a real machinistst' world,
a "drill bit" belongs with a "brace" as in an auger, for ship use.
........just being a real machinist asshole.
Suggest that you look up drill bits. No mention of braces or augers.
 

p-moon

Aluminum
Joined
Apr 2, 2005
Location
indiana
I prefer a hurty gurty ;)

6 sided collet block works well too.
I have found that it is easier to get something running true in a whirly gig, hurdy gurdy, spin fixture, harig head, whatever. Collets just don't hold stuff that concentric. Maybe that is my mold shop background?
 

Nmbmxer

Hot Rolled
Joined
Jun 22, 2008
Location
VA
Back in the day ,they used to put a spot of mig on the end of the shank to stop drills slipping in Jacobs chucks that were a bit worn.
The fab guy at the last place I worked would do this with a tig tack. As was stated earlier to was to prevent the chuck from slipping if the bit grabbed when using a cordless drill motor and not for use in a machine with a good quality chuck.
 








 
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