Reducing diameter of straight drill bits
Ignoramus17356
drill press.
I do not have a reduced shank 21/32 drill bit and new they cost $30+.
I have a 21/32 straight shank drill bit, but it is too wide to fit any
of my handheld electric drills, which go up to 1/2".
I thought I could reduce a shank of that drill bit by simply chucking
it in a lathe and taking off some diameter with a carbide tool. What
are the drawbacks, if any, of doing so?
i
azotic
"Ignoramus17356" <ignoram...@NOSPAM.17356.invalid> wrote in message
news:5budncWeAOP5iyHW...@giganews.com...
Hold the drill using a 5C collet, or use a 4 jaw chuck and indicate the
drill
till it runs true. If you use a 3 jaw chuck you may encounter some runout.
Best Regards
Tom.
Jeff R.
"azotic" <azo...@cox.net> wrote in message
news:FvVun.166725$2r7....@newsfe05.iad...
...and you won't need a carbide tool ('though it won't hurt).
Drill shanks are nice and soft, and easy to machine. I use HSS tools with
excellent results.
--
Jeff R.
Jim Wilkins
17356.invalid> wrote:
> ...
>
> I thought I could reduce a shank of that drill bit by simply chucking
> it in a lathe and taking off some diameter with a carbide tool. What
> are the drawbacks, if any, of doing so?
>
> i
HSS drill bits are easy to turn smaller but then they slip more easily
in the chuck. If you have 5C collets and a hex block or indexer you
could mill three flats to get it into the drill chuck.
21/32" is the tap drill for 3/4-10 so I wouldn't change it enough that
it no longer fits the larger chuck.
jsw
Ignoramus8052
> On Apr 7, 1:21?am, Ignoramus17356 <ignoramus17...@NOSPAM.
> 17356.invalid> wrote:
>> ...
>>
>> I thought I could reduce a shank of that drill bit by simply chucking
>> it in a lathe and taking off some diameter with a carbide tool. What
>> are the drawbacks, if any, of doing so?
>>
>> i
>
> HSS drill bits are easy to turn smaller but then they slip more easily
> in the chuck. If you have 5C collets and a hex block or indexer you
> could mill three flats to get it into the drill chuck.
Yes, I have one, and I will do just that, great idea. I did plan on
doing that.
> 21/32" is the tap drill for 3/4-10 so I wouldn't change it enough
Exactly why I need it, to tap 3/4-10 thread.
sta...@prolynx.com
As the others have said, the shanks are soft. Just don't leave a
sharp corner where you turn the thing down, if the drill jams up, it
could leave you with a twisted-off shank in the chuck and the drill
stuck in the work. That's if you've got a drill that can wrap you up
if it jams. Some of the cheapies will just stall out.
Stan
Ignoramus8052
> As the others have said, the shanks are soft. Just don't leave a
> sharp corner where you turn the thing down, if the drill jams up, it
> could leave you with a twisted-off shank in the chuck and the drill
> stuck in the work. That's if you've got a drill that can wrap you up
> if it jams. Some of the cheapies will just stall out.
I have two drills like that, that could twist my arms. I prefer using
the less powerful drills where possible. It is a very unpleasant
sensation. The application is to enlarge a 5/8 nominal hole to become
a 21/32 hole, and to later tap it for 3/4-10 thread.
This is actually to move that Bridgeport Interact II.
i
Bill Martin
Be really careful.. a big starter hole like that will want to grab the
drill bit and twist it, with significant force on "you". Any way you can
grind a pilot on the end of the drill bit that fits the original hole?
-bill
Joseph Gwinn
Ignoramus8052 <ignora...@NOSPAM.8052.invalid> wrote:
What is the material being drilled? Steel is guaranteed to grab and make the
drill try to tear your arm off. Cast iron would be easier, if the drill is
dressed as for drilling brass.
> This is actually to move that Bridgeport Interact II.
Why is 5/8" too small?
Is there sufficient remaining meat around the hole if it is enlarged?
Joe Gwinn
Ignoramus16651
> In article <_KKdnfHyxPkPISHW...@giganews.com>,
> Ignoramus8052 <ignora...@NOSPAM.8052.invalid> wrote:
>
>> On 2010-04-07, sta...@prolynx.com <sta...@prolynx.com> wrote:
>> > As the others have said, the shanks are soft. Just don't leave a
>> > sharp corner where you turn the thing down, if the drill jams up, it
>> > could leave you with a twisted-off shank in the chuck and the drill
>> > stuck in the work. That's if you've got a drill that can wrap you up
>> > if it jams. Some of the cheapies will just stall out.
>>
>> I have two drills like that, that could twist my arms. I prefer using
>> the less powerful drills where possible. It is a very unpleasant
>> sensation. The application is to enlarge a 5/8 nominal hole to become
>> a 21/32 hole, and to later tap it for 3/4-10 thread.
>
> What is the material being drilled? Steel is guaranteed to grab and make the
> drill try to tear your arm off. Cast iron would be easier, if the drill is
> dressed as for drilling brass.
Cast iron
>
>> This is actually to move that Bridgeport Interact II.
>
> Why is 5/8" too small?
The hole is 5/8". I need to tap it for 3/4-10. Thus I need to enlarge
the hole to 21/32.
> Is there sufficient remaining meat around the hole if it is enlarged?
Yes.
i
Leon Fisk
Ignoramus16651 <ignoram...@NOSPAM.16651.invalid> wrote:
<snip>
>>> I have two drills like that, that could twist my arms. I prefer using
>>> the less powerful drills where possible. It is a very unpleasant
>>> sensation. The application is to enlarge a 5/8 nominal hole to become
>>> a 21/32 hole, and to later tap it for 3/4-10 thread.
I'm sure you have bigger chucks in your stash, couldn't you just make
an adapter to mount a larger chuck in the smaller chuck? Shouldn't
really cause any trouble with hand-held work other than making it a bit
longer.
--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email
Joseph Gwinn
Ignoramus16651 <ignoram...@NOSPAM.16651.invalid> wrote:
> On 2010-04-08, Joseph Gwinn <joeg...@comcast.net> wrote:
> > In article <_KKdnfHyxPkPISHW...@giganews.com>,
> > Ignoramus8052 <ignora...@NOSPAM.8052.invalid> wrote:
> >
> >> On 2010-04-07, sta...@prolynx.com <sta...@prolynx.com> wrote:
> >> > As the others have said, the shanks are soft. Just don't leave a
> >> > sharp corner where you turn the thing down, if the drill jams up, it
> >> > could leave you with a twisted-off shank in the chuck and the drill
> >> > stuck in the work. That's if you've got a drill that can wrap you up
> >> > if it jams. Some of the cheapies will just stall out.
> >>
> >> I have two drills like that, that could twist my arms. I prefer using
> >> the less powerful drills where possible. It is a very unpleasant
> >> sensation. The application is to enlarge a 5/8 nominal hole to become
> >> a 21/32 hole, and to later tap it for 3/4-10 thread.
> >
> > What is the material being drilled? Steel is guaranteed to grab and make
> > the drill try to tear your arm off. Cast iron would be easier, if the drill is
> > dressed as for drilling brass.
>
> Cast iron
Ahh. Machine base of the mill, then.
> >> This is actually to move that Bridgeport Interact II.
> >
> > Why is 5/8" too small?
>
> The hole is 5/8". I need to tap it for 3/4-10. Thus I need to enlarge
> the hole to 21/32.
This is an answer to the question "What?", but is not an answer to the question
"Why?"
> > Is there sufficient remaining meat around the hole if it is enlarged?
>
> Yes.
Good iron.
Joe Gwinn
DoN. Nichols
> I need to drill some 21/32 holes with a hand drill, not accessible to
> drill press.
>
> I do not have a reduced shank 21/32 drill bit and new they cost $30+.
[ ... ]
> I thought I could reduce a shank of that drill bit by simply chucking
> it in a lathe and taking off some diameter with a carbide tool. What
> are the drawbacks, if any, of doing so?
Typically -- you won't even need carbide. The shank of most
drills is mild steel, joined to the HSS for the working end. This is so
the chuck jaws can dig in a bit to get a better grip.
If you have to clamp it in the lathe chuck on the flutes (the
shank is too short), what I would suggest is getting a length of copper
1/2" tubing, slit it along the length, and slide it over the flutes to
act as a sacrificial surface to clamp on.
And next time a surplus lot gives you a batch of Silver &
Demming drill bits (the reduced shank ones) remember this, and instead
of putting them on eBay, save them for your own needs. (I suspect that
you have already had and sold more than one set. :-)
Good Luck,
DoN.
--
Email: <dnic...@d-and-d.com> | 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 ---
John
Just chuck the drill up and turn the shank. Then grind a small (say
1/16") flat on the cutting edges In other words take out all the side
rake on the cutting edge (look at the cutting end with the shank up)
just as you would if you were sharpening for brass or other soft
material. Then have at it.
What is it that Nike says?
Cheers,
John D.
(jdslocombatgmail)
Ignoramus21954
> On 2010-04-07, Ignoramus17356 <ignoram...@NOSPAM.17356.invalid> wrote:
>> I need to drill some 21/32 holes with a hand drill, not accessible to
>> drill press.
>>
>> I do not have a reduced shank 21/32 drill bit and new they cost $30+.
>
> [ ... ]
>
>> I thought I could reduce a shank of that drill bit by simply chucking
>> it in a lathe and taking off some diameter with a carbide tool. What
>> are the drawbacks, if any, of doing so?
>
> Typically -- you won't even need carbide. The shank of most
> drills is mild steel, joined to the HSS for the working end. This is so
> the chuck jaws can dig in a bit to get a better grip.
>
> If you have to clamp it in the lathe chuck on the flutes (the
> shank is too short), what I would suggest is getting a length of copper
> 1/2" tubing, slit it along the length, and slide it over the flutes to
> act as a sacrificial surface to clamp on.
>
> And next time a surplus lot gives you a batch of Silver &
> Demming drill bits (the reduced shank ones) remember this, and instead
> of putting them on eBay, save them for your own needs. (I suspect that
> you have already had and sold more than one set. :-)
I actually have quite a few of S&D drills, but not in 21/32.
I regret selling a lot of things... But I am space limited.
i
Jim Wilkins
drill bits by making a half-round piloted step drill out of O-1. I
can't find it right now but I think light blue was the right temper,
on the third try. It cut reasonably well without any back rake, using
a lot of pressure. The truck's owner and I took turns crawling
underneath and heaving on the drill.
jsw