I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl

Karl Townsend wrote:
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl



100 years ago was still gun drilling times like current methods. Prior
to that the barrel was hammer formed over a mandrel.

--
Steve W.

On Sat, 11 Feb 2012 21:59:05 -0500, Steve W. wrote:

Karl Townsend wrote:
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/
frequently_asked_questions_about_drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl



100 years ago was still gun drilling times like current methods. Prior
to that the barrel was hammer formed over a mandrel.

How did they manage to maintain accuracy under such conditions? Or did
each gun just end up having "character"?

And how did they get those poor monkeys to sit still for such abuse?

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

"Karl Townsend" wrote in message
...
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.


Probly find some info here http://www.kays-dehoff.com/ they are probably
the largest US firm

Used to do a lot of it at the lazy b but usually in round rod if it was
important that the hole be perfectly centered at both ends then we'd just go
ahead and let the drill wander...re-pick-up hole center at the exit end
after the fact and then finally we'd finish the OD

"Karl Townsend" wrote in message
...

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
__________________________________________________ ____________

How good do the holes have to be?

On Sun, 12 Feb 2012 04:34:13 -0500, "Tom Gardner"
wrote:



"Karl Townsend" wrote in message
.. .

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
_________________________________________________ _____________

How good do the holes have to be?


If you go further enough back they probably welded the barrel around a
mandrill and then reamed to size. But in reading several books by
various gunsmiths who were in the trade in the early 1900's, they
drilled the initial hole somewhat undersize and then used special
reamers to straighten the hole and bring it to size. They probably
also straightened the barrels as a final step.

The U shaped drill tubes and the pressure oil feed down the tube both
lubricated the drill and flushed the chips out of the hole. The actual
cutting bit was a single flute drill and the drilling machines were
said to be high RPM and low feed rate.

I'm sure that you have looked at the web but this site is pr

For a more detailed look you might try
http://firearmsid.com/Feature%20Arti...anufacture.htm
which is a sort of modern method of doing it the way it used to be
done :-)

or Lilja's site
http://www.riflebarrels.com/articles...fle_barrel.htm

All of the instructions I have ever seen emphasized the "U" shaped
drill rods and the high pressure oil to wash the chips out of the
hole.

--
Cheers

John B.

"Steve W." wrote in message
...
Karl Townsend wrote:

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.
Karl

100 years ago was still gun drilling times like current methods. Prior to
that the barrel was hammer formed over a mandrel.
Steve W.

http://www.technidrillsystems.com/faq.htm
http://www.lindsaybks.com/bks5/deep/index.html

http://en.wikipedia.org/wiki/John_Wi...(industrialist)
http://en.wikipedia.org/wiki/Bersham_Ironworks
http://www.wrexham.gov.uk/english/he...ing_cannon.htm

jsw

On Sun, 12 Feb 2012 06:55:24 -0500, "Jim Wilkins"
wrote:


"Steve W." wrote in message
...
Karl Townsend wrote:

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.
Karl

100 years ago was still gun drilling times like current methods. Prior to
that the barrel was hammer formed over a mandrel.
Steve W.

http://www.technidrillsystems.com/faq.htm
http://www.lindsaybks.com/bks5/deep/index.html

http://en.wikipedia.org/wiki/John_Wi...(industrialist)
http://en.wikipedia.org/wiki/Bersham_Ironworks
http://www.wrexham.gov.uk/english/he...ing_cannon.htm

jsw


thanks for the links. I'll order that lindsay book.

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl

If you had a great need for a gun drill...I have an Eldorado Id sell
cheaply.

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

On Feb 11, 6:43*pm, Karl Townsend
wrote:
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.http://www.sterlinggundrills.com/fre...ions_about_dri...

Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl

See Howe's "The Modern Gunsmith". Has the complete setup, drill bit
shape, support, plumbing, everything. The bit, when properly shaped
and started, is self-centering. Lindsey had a book on making rifle
barrels, mostly extracts from WWI-era machining magazines. Has a
little more on the pitfalls and problems seen in production. The old-
timers used high-pressure cutting oil for clearing chips and lots of
it. The Lindsey book mentions a basement of oil tanks and gutters in
the machine room for oil return. It isn't that coolant isn't needed,
it's the chip clearing function that needs the flow, I doubt if a mist
will do that.

Stan

On 2012-02-12, Stanley Schaefer wrote:
On Feb 11, 6:43?pm, Karl Townsend
wrote:
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.http://www.sterlinggundrills.com/fre...ions_about_dri...

Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl

See Howe's "The Modern Gunsmith". Has the complete setup, drill bit
shape, support, plumbing, everything. The bit, when properly shaped
and started, is self-centering. Lindsey had a book on making rifle
barrels, mostly extracts from WWI-era machining magazines. Has a
little more on the pitfalls and problems seen in production. The old-
timers used high-pressure cutting oil for clearing chips and lots of
it. The Lindsey book mentions a basement of oil tanks and gutters in
the machine room for oil return. It isn't that coolant isn't needed,
it's the chip clearing function that needs the flow, I doubt if a mist
will do that.

Stan

Stan, what about peck drilling with CNC? It may take a lot longer than
with high pressure oil, but it should work, right?

i

See Howe's "The Modern Gunsmith". Has the complete setup, drill bit
shape, support, plumbing, everything. The bit, when properly shaped
and started, is self-centering. Lindsey had a book on making rifle
barrels, mostly extracts from WWI-era machining magazines. Has a
little more on the pitfalls and problems seen in production. The old-
timers used high-pressure cutting oil for clearing chips and lots of
it. The Lindsey book mentions a basement of oil tanks and gutters in
the machine room for oil return. It isn't that coolant isn't needed,
it's the chip clearing function that needs the flow, I doubt if a mist
will do that.

Stan

Thnaks, I found the book on the net and downloaded it.

If you had a great need for a gun drill...I have an Eldorado Id sell
cheaply.

I'd buy a bunch of the drills and a high pressure pump. Just don't
have the room for another machine. Looks like the CHNC will do a fine
job for my needs

Karl

Ignoramus17548 fired this volley in
:

Stan, what about peck drilling with CNC? It may take a lot longer than
with high pressure oil, but it should work, right?


Ig, peck drilling holes deeper than about 10xD tends to bell the mouth of
the hole.

A common twist drill isn't terribly rigid, nor terribly straight, as
tools go. It wiggles just a bit about its center, even if it's
accurately sharpened with the tip exactly centered. And any runout in
the setup, spindle, chuck, collet, or arbor exacerbates that.

So, although it tends to self-center IN the hole, it doesn't make a hole
exactly its own diameter until it's fairly deeply embedded in the work.

Pecking worsens that, because each time it enters the hole, it deepens
that enlarged part of the hole. The hole ends up somewhat "bell shaped",
more and more, the more pecks that are taken.

That's fine for (most) bolt holes. Not for a precision bore.

If he needs "just a hole", peck drilling will work fine. If he needs an
accurate "bore", no.

Of course, one can drill undersized by a couple of thou, then ream to
size.

LLoyd

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
Greetings Karl,
I have several drills with coolant holes in them that range in size
from less than .300 to about .750 dia. Some of these drills are over
12 inches long. Even the skinny ones. They have a threaded shank with
a beveled shoulder and thread into a coolant inducing rotary union.
The union has a shank that goes into the spindle and drives the drill.
They were originally used on a big CNC mill for drilling deep holes in
steel parts. I can try to find out who makes them if you would like.
They might be just what you need.
Eric

On Sun, 12 Feb 2012 11:53:50 -0800, wrote:

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
Greetings Karl,
I have several drills with coolant holes in them that range in size
from less than .300 to about .750 dia. Some of these drills are over
12 inches long. Even the skinny ones. They have a threaded shank with
a beveled shoulder and thread into a coolant inducing rotary union.
The union has a shank that goes into the spindle and drives the drill.
They were originally used on a big CNC mill for drilling deep holes in
steel parts. I can try to find out who makes them if you would like.
They might be just what you need.
Eric

When it comes to drilling straight holes, the through-hole coolant is
not the big issue, Eric. The big issue is single-point cutting with a
"backside" of the cutter that bears on the hole as it's cut.

It shares some characteristics with single-point boring -- primarily
that the deflecting load on the cutter is uniform around the periphery
of the hole -- but it's different in that the tool actually bears
against the hole, making rigidity of the drill shank a minor issue.

If you start a gundrill straight, and if the material you're cutting
is clean and homogeneous, it will cut straight, even though the drill
shank will flex.

This is not true with any kind of multi-edge drill, whether it's a
conventional twist drill, or an insert type, or a spade drill.

The high-pressure lubricant/coolant is necessary because this kind of
cutting is a chip-jamming nightmare. You absolutely need it beyond
certain very low depth/diameter ratios.

--
Ed Huntress

On Sun, 12 Feb 2012 15:10:37 -0500, Ed Huntress
wrote:

On Sun, 12 Feb 2012 11:53:50 -0800, wrote:

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
Greetings Karl,
I have several drills with coolant holes in them that range in size
from less than .300 to about .750 dia. Some of these drills are over
12 inches long. Even the skinny ones. They have a threaded shank with
a beveled shoulder and thread into a coolant inducing rotary union.
The union has a shank that goes into the spindle and drives the drill.
They were originally used on a big CNC mill for drilling deep holes in
steel parts. I can try to find out who makes them if you would like.
They might be just what you need.
Eric

When it comes to drilling straight holes, the through-hole coolant is
not the big issue, Eric. The big issue is single-point cutting with a
"backside" of the cutter that bears on the hole as it's cut.

It shares some characteristics with single-point boring -- primarily
that the deflecting load on the cutter is uniform around the periphery
of the hole -- but it's different in that the tool actually bears
against the hole, making rigidity of the drill shank a minor issue.

If you start a gundrill straight, and if the material you're cutting
is clean and homogeneous, it will cut straight, even though the drill
shank will flex.

This is not true with any kind of multi-edge drill, whether it's a
conventional twist drill, or an insert type, or a spade drill.

The high-pressure lubricant/coolant is necessary because this kind of
cutting is a chip-jamming nightmare. You absolutely need it beyond
certain very low depth/diameter ratios.
ED,
The last shop I worked in had several gundrills. We drilled holes from
as small as 1/16" to over 2". I learned how to sharpen gundrills and
understand how they work. I can't count how many bushings I made for
starting gundrills on location. The drills I have are Guring drills
and the guy I got them was drilling very straight holes with them. I
know they don't work the same as gundrills. Being used in a mill may
be why they drilled such straight holes because they were fed
straight. They didn't require really high pressure coolant to clear
the chips. But I watched them drilling parts and the drills were being
pecked. Unlike gundrills which just keep on going.
Eric

Karl Townsend wrote:

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Sometimes a fat piece of metal was heated up, put over a mandrill and run through a
rolling stand. Then it was re-heated, placed over a smaller mandril and run through
again. Repeat until you get what you want.

Sorry for not answering your question but drilling a long hole a long time ago was hard to
do so they found another way.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

wrote in message
...

...The drills I have are Guring drills
and the guy I got them was drilling very straight holes with them. I
know they don't work the same as gundrills. Being used in a mill may
be why they drilled such straight holes because they were fed
straight. They didn't require really high pressure coolant to clear
the chips. But I watched them drilling parts and the drills were being
pecked. Unlike gundrills which just keep on going.
Eric

Since you spelled the name phonetically;
http://www.guhring.com/Documents/Cat...pHoleFlyer.pdf

jsw

On Sun, 12 Feb 2012 15:33:42 -0800, wrote:

On Sun, 12 Feb 2012 15:10:37 -0500, Ed Huntress
wrote:

On Sun, 12 Feb 2012 11:53:50 -0800, wrote:

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
Greetings Karl,
I have several drills with coolant holes in them that range in size
from less than .300 to about .750 dia. Some of these drills are over
12 inches long. Even the skinny ones. They have a threaded shank with
a beveled shoulder and thread into a coolant inducing rotary union.
The union has a shank that goes into the spindle and drives the drill.
They were originally used on a big CNC mill for drilling deep holes in
steel parts. I can try to find out who makes them if you would like.
They might be just what you need.
Eric

When it comes to drilling straight holes, the through-hole coolant is
not the big issue, Eric. The big issue is single-point cutting with a
"backside" of the cutter that bears on the hole as it's cut.

It shares some characteristics with single-point boring -- primarily
that the deflecting load on the cutter is uniform around the periphery
of the hole -- but it's different in that the tool actually bears
against the hole, making rigidity of the drill shank a minor issue.

If you start a gundrill straight, and if the material you're cutting
is clean and homogeneous, it will cut straight, even though the drill
shank will flex.

This is not true with any kind of multi-edge drill, whether it's a
conventional twist drill, or an insert type, or a spade drill.

The high-pressure lubricant/coolant is necessary because this kind of
cutting is a chip-jamming nightmare. You absolutely need it beyond
certain very low depth/diameter ratios.
ED,
The last shop I worked in had several gundrills. We drilled holes from
as small as 1/16" to over 2". I learned how to sharpen gundrills and
understand how they work. I can't count how many bushings I made for
starting gundrills on location. The drills I have are Guring drills
and the guy I got them was drilling very straight holes with them. I
know they don't work the same as gundrills. Being used in a mill may
be why they drilled such straight holes because they were fed
straight. They didn't require really high pressure coolant to clear
the chips. But I watched them drilling parts and the drills were being
pecked. Unlike gundrills which just keep on going.
Eric

There are several techiques for drilling straight holes, including
using a combination of workpiece rotation and tool rotation (used in
high-end gundrilling, too). And Guhring makes very accurate cutting
tools.

But once you exceed the depth ratio that allows the drill shank to
contribute to centering and if you take away that bushing effect
opposite the cutting edge, you're depending on everything being
near-perfect: -- which it rarely is. Multi-spindle production
gundrilling machines actually are pretty crude machines, or they were.

Pecking and multiple flutes, too, will make clearing chips a lot
easier. I've watched gun drilling at Colt, Remington (back in the
'70s), as well as some ECM gun-barrel operations, and I was always
amazed at how they could center those holes so well in all of that
lubricant mess and with all of that rattling going on.

I don't doubt your success at drilling straight holes with other
drills, Erik, but I think it takes more than a good drill bit to do
it.

--
Ed Huntress

On Sun, 12 Feb 2012 18:48:25 -0500, "Jim Wilkins"
wrote:


wrote in message
.. .

...The drills I have are Guring drills
and the guy I got them was drilling very straight holes with them. I
know they don't work the same as gundrills. Being used in a mill may
be why they drilled such straight holes because they were fed
straight. They didn't require really high pressure coolant to clear
the chips. But I watched them drilling parts and the drills were being
pecked. Unlike gundrills which just keep on going.
Eric

Since you spelled the name phonetically;
http://www.guhring.com/Documents/Cat...pHoleFlyer.pdf

jsw

Oh crap. I know better. I should spell check better. I had just looked
at the drills about 30 minutes before the post too.
Eric

On Sun, 12 Feb 2012 19:39:01 -0500, Ed Huntress
wrote:

On Sun, 12 Feb 2012 15:33:42 -0800, wrote:

On Sun, 12 Feb 2012 15:10:37 -0500, Ed Huntress
wrote:

On Sun, 12 Feb 2012 11:53:50 -0800, wrote:

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
Greetings Karl,
I have several drills with coolant holes in them that range in size
from less than .300 to about .750 dia. Some of these drills are over
12 inches long. Even the skinny ones. They have a threaded shank with
a beveled shoulder and thread into a coolant inducing rotary union.
The union has a shank that goes into the spindle and drives the drill.
They were originally used on a big CNC mill for drilling deep holes in
steel parts. I can try to find out who makes them if you would like.
They might be just what you need.
Eric

When it comes to drilling straight holes, the through-hole coolant is
not the big issue, Eric. The big issue is single-point cutting with a
"backside" of the cutter that bears on the hole as it's cut.

It shares some characteristics with single-point boring -- primarily
that the deflecting load on the cutter is uniform around the periphery
of the hole -- but it's different in that the tool actually bears
against the hole, making rigidity of the drill shank a minor issue.

If you start a gundrill straight, and if the material you're cutting
is clean and homogeneous, it will cut straight, even though the drill
shank will flex.

This is not true with any kind of multi-edge drill, whether it's a
conventional twist drill, or an insert type, or a spade drill.

The high-pressure lubricant/coolant is necessary because this kind of
cutting is a chip-jamming nightmare. You absolutely need it beyond
certain very low depth/diameter ratios.
ED,
The last shop I worked in had several gundrills. We drilled holes from
as small as 1/16" to over 2". I learned how to sharpen gundrills and
understand how they work. I can't count how many bushings I made for
starting gundrills on location. The drills I have are Guring drills
and the guy I got them was drilling very straight holes with them. I
know they don't work the same as gundrills. Being used in a mill may
be why they drilled such straight holes because they were fed
straight. They didn't require really high pressure coolant to clear
the chips. But I watched them drilling parts and the drills were being
pecked. Unlike gundrills which just keep on going.
Eric

There are several techiques for drilling straight holes, including
using a combination of workpiece rotation and tool rotation (used in
high-end gundrilling, too). And Guhring makes very accurate cutting
tools.

But once you exceed the depth ratio that allows the drill shank to
contribute to centering and if you take away that bushing effect
opposite the cutting edge, you're depending on everything being
near-perfect: -- which it rarely is. Multi-spindle production
gundrilling machines actually are pretty crude machines, or they were.

Pecking and multiple flutes, too, will make clearing chips a lot
easier. I've watched gun drilling at Colt, Remington (back in the
'70s), as well as some ECM gun-barrel operations, and I was always
amazed at how they could center those holes so well in all of that
lubricant mess and with all of that rattling going on.

I don't doubt your success at drilling straight holes with other
drills, Erik, but I think it takes more than a good drill bit to do
it.
Well sure Ed. It takes a good setup too. With gundrills getting the
hole started is key. With thinner drills we had to use whip guides on
the unsupported shank of the drill before it entered the hole. But the
guides were fairly loose so the shank on thin drills would still whip
around in a small circle. And the noise from the larger drills when
drilling some materials was so loud we all had to wear earplugs under
ear muffs. I'm still surprised the carbide tips didn't fracture from
the chatter that was making all the noise. We used hardened bushings
honed to the drill tip's exact size to insure a good on size start to
the hole.
Eric

On Sun, 12 Feb 2012 18:41:28 -0800, wrote:

On Sun, 12 Feb 2012 19:39:01 -0500, Ed Huntress
wrote:

On Sun, 12 Feb 2012 15:33:42 -0800, wrote:

On Sun, 12 Feb 2012 15:10:37 -0500, Ed Huntress
wrote:

On Sun, 12 Feb 2012 11:53:50 -0800, wrote:

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl
Greetings Karl,
I have several drills with coolant holes in them that range in size
from less than .300 to about .750 dia. Some of these drills are over
12 inches long. Even the skinny ones. They have a threaded shank with
a beveled shoulder and thread into a coolant inducing rotary union.
The union has a shank that goes into the spindle and drives the drill.
They were originally used on a big CNC mill for drilling deep holes in
steel parts. I can try to find out who makes them if you would like.
They might be just what you need.
Eric

When it comes to drilling straight holes, the through-hole coolant is
not the big issue, Eric. The big issue is single-point cutting with a
"backside" of the cutter that bears on the hole as it's cut.

It shares some characteristics with single-point boring -- primarily
that the deflecting load on the cutter is uniform around the periphery
of the hole -- but it's different in that the tool actually bears
against the hole, making rigidity of the drill shank a minor issue.

If you start a gundrill straight, and if the material you're cutting
is clean and homogeneous, it will cut straight, even though the drill
shank will flex.

This is not true with any kind of multi-edge drill, whether it's a
conventional twist drill, or an insert type, or a spade drill.

The high-pressure lubricant/coolant is necessary because this kind of
cutting is a chip-jamming nightmare. You absolutely need it beyond
certain very low depth/diameter ratios.
ED,
The last shop I worked in had several gundrills. We drilled holes from
as small as 1/16" to over 2". I learned how to sharpen gundrills and
understand how they work. I can't count how many bushings I made for
starting gundrills on location. The drills I have are Guring drills
and the guy I got them was drilling very straight holes with them. I
know they don't work the same as gundrills. Being used in a mill may
be why they drilled such straight holes because they were fed
straight. They didn't require really high pressure coolant to clear
the chips. But I watched them drilling parts and the drills were being
pecked. Unlike gundrills which just keep on going.
Eric

There are several techiques for drilling straight holes, including
using a combination of workpiece rotation and tool rotation (used in
high-end gundrilling, too). And Guhring makes very accurate cutting
tools.

But once you exceed the depth ratio that allows the drill shank to
contribute to centering and if you take away that bushing effect
opposite the cutting edge, you're depending on everything being
near-perfect: -- which it rarely is. Multi-spindle production
gundrilling machines actually are pretty crude machines, or they were.

Pecking and multiple flutes, too, will make clearing chips a lot
easier. I've watched gun drilling at Colt, Remington (back in the
'70s), as well as some ECM gun-barrel operations, and I was always
amazed at how they could center those holes so well in all of that
lubricant mess and with all of that rattling going on.

I don't doubt your success at drilling straight holes with other
drills, Erik, but I think it takes more than a good drill bit to do
it.
Well sure Ed. It takes a good setup too. With gundrills getting the
hole started is key. With thinner drills we had to use whip guides on
the unsupported shank of the drill before it entered the hole. But the
guides were fairly loose so the shank on thin drills would still whip
around in a small circle. And the noise from the larger drills when
drilling some materials was so loud we all had to wear earplugs under
ear muffs. I'm still surprised the carbide tips didn't fracture from
the chatter that was making all the noise. We used hardened bushings
honed to the drill tip's exact size to insure a good on size start to
the hole.
Eric

Hah! Yes, that sounds familiar. The rattling and whipping around were
the biggest surprises to me when I first saw gundrilling operations.
Here was a high-precision machining operation and it sounded like a
cross between a popcorn popper and a Caribbean steel band.

Well, I've spent some time with the Guehring people and I have the
highest respect for their tools. I'm sure your experience with those
setups can teach us a few things.

--
Ed Huntress

On Sat, 11 Feb 2012 19:43:31 -0600, Karl Townsend
wrote:

I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl


Hey Karl,

No expert here, but gun-drills and gundrilling require the high
pressure "oil" . It is not there so much as a lubricant, but to
remove the swarf as it is generated. If the swarf is not removed, it
won't drill, or at least not straight. Just "lubricating" or coolant
won't cut it !!

Assuming that you can get high-pressure through the drill, CNC should
work fine, although if it is a long bore you will need some sort of
shank support.

All the accuracy in a gun-drill is in the form of the tip. Look very
closely at how it works.

Take care. Good luck.

Brian Lawson,
Bothwell, Ontario.

On 2/11/2012 8:43 PM, Karl Townsend wrote:
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml


Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl



Karl,

We gun drill in our CNC lathe some. We end up hooking up a pressure
washer to the coolant lines and use that as a high pressure pump. It
works pretty good. Also we gun drill on our horizontal mills, it goes a
bit slower, but works for what we need.

On 2/14/2012 7:37 AM, tnik wrote:
On 2/11/2012 8:43 PM, Karl Townsend wrote:
I have a need for several 0.350" holes 10.5" deep in 4140 rod...

Been looking to buy something close, no joy so far.

I came accross this gundrilling FAQ. It states gundrilling can be done
on a CNC lathe like mine.
http://www.sterlinggundrills.com/fre...drilling.shtml



Anyone have experience with gundrilling on a CNC lathe? I know i can't
go with the high pressue oil I've seen on regular gundrills. The above
FAQ mentions a spray mist system. I could go with high flow coolant as
my CNC lathe is enclosed.

Anyone know how gundrilling was done 100 years ago? Bet the same
technique would work today.

Karl



Karl,

We gun drill in our CNC lathe some. We end up hooking up a pressure
washer to the coolant lines and use that as a high pressure pump. It
works pretty good. Also we gun drill on our horizontal mills, it goes a
bit slower, but works for what we need.

Also, we normally either have a bushing help to start the hole, or we
bore and/or ream a pilot hole. Once we have a straight hole to start the
gun drill, it goes nice and straight.

We gun drill in our CNC lathe some. We end up hooking up a pressure
washer to the coolant lines and use that as a high pressure pump. It
works pretty good. Also we gun drill on our horizontal mills, it goes a
bit slower, but works for what we need.

Also, we normally either have a bushing help to start the hole, or we
bore and/or ream a pilot hole. Once we have a straight hole to start the
gun drill, it goes nice and straight.

Thanks, good to know this has been done. Just what i'm going to try.
Could you give me some speeds and feeds for the size drills you've
run?