Folks, I'm looking at boring a 5/8 inch diameter by 5 inch long hole
through 4140 PH, so I can make a barrel stub for my TC Contender.

From initial comments, I'll need carbide to do this... BUT... pure
carbide needs rigid setup, which I don't believe my Grizzly G9972Z lathe
has. Once I punch through a 1/2" hole, then I can whip out my CCMT
boring bar and do it.

Will HSS or cobalt drills get er done?

Heat treating would add more cost to this than it's worth. Really, if I
could find a clapped-out Contender barrel, I'd saw the barrel off, bore
it, and stub it. But barrels are not cheap on ebuy...

On Sun, 29 Jan 2012 20:37:15 -0600, Louis Ohland
wrote:

Folks, I'm looking at boring a 5/8 inch diameter by 5 inch long hole
through 4140 PH, so I can make a barrel stub for my TC Contender.

From initial comments, I'll need carbide to do this... BUT... pure
carbide needs rigid setup, which I don't believe my Grizzly G9972Z lathe
has. Once I punch through a 1/2" hole, then I can whip out my CCMT
boring bar and do it.

Will HSS or cobalt drills get er done?

Pre-hardened 4140 maxes out at Rc 32 if it was treated properly. You
should be able to do that with M42 ("cobalt") with no trouble.
Probably M4, for that matter.


Heat treating would add more cost to this than it's worth. Really, if I
could find a clapped-out Contender barrel, I'd saw the barrel off, bore
it, and stub it. But barrels are not cheap on ebuy...

On 1/30/2012 2:53 PM, Ed Huntress wrote:


Pre-hardened 4140 maxes out at Rc 32 if it was treated properly. You
should be able to do that with M42 ("cobalt") with no trouble.
Probably M4, for that matter.


Agree. I made some parts with it, and found it tougher than mild steel
but still very manageable with HSS cutters.

"Jordan" wrote in message
...
On 1/30/2012 2:53 PM, Ed Huntress wrote:


Pre-hardened 4140 maxes out at Rc 32 if it was treated properly. You
should be able to do that with M42 ("cobalt") with no trouble.
Probably M4, for that matter.


Agree. I made some parts with it, and found it tougher than mild steel but
still very manageable with HSS cutters.

I'm curious about 4140HT too, so I just faced some with HSS, no cutting oil,
and it cut as easily as drill rod or a Grade 5 bolt.

jsw

On Sun, 29 Jan 2012 20:37:15 -0600, Louis Ohland
wrote:

Folks, I'm looking at boring a 5/8 inch diameter by 5 inch long hole
through 4140 PH, so I can make a barrel stub for my TC Contender.

From initial comments, I'll need carbide to do this... BUT... pure
carbide needs rigid setup, which I don't believe my Grizzly G9972Z lathe
has. Once I punch through a 1/2" hole, then I can whip out my CCMT
boring bar and do it.

Will HSS or cobalt drills get er done?

Heat treating would add more cost to this than it's worth. Really, if I
could find a clapped-out Contender barrel, I'd saw the barrel off, bore
it, and stub it. But barrels are not cheap on ebuy...
Greetings Louis,
Cobalt drill would be better but HSS will work too. As a bonus to the
hardness you will find that you can get an excellent finish on the
stuff using carbide. I would rather machine 4140 and 4340 in the heat
treated condition just because it looks so much better. And the nicer
finish also makes it easier to hold tighter tolerances.
Eric

Did some measurements, stub length is about 2 1/4 ".

Looking for 7/8 thick x 1 5/8 wide by 2.25" long 4140 HT (or
thereabouts). Speedy metals has 7/8 x 2.5 flats, but I'd rather have
stock that is fairly square lengthwise, I can always face to length.

Greetings Louis,
Cobalt drill would be better but HSS will work too. As a bonus to the
hardness you will find that you can get an excellent finish on the
stuff using carbide. I would rather machine 4140 and 4340 in the heat
treated condition just because it looks so much better. And the nicer
finish also makes it easier to hold tighter tolerances.
Eric

On Sun, 29 Jan 2012 20:37:15 -0600, Louis Ohland wrote:

Folks, I'm looking at boring a 5/8 inch diameter by 5 inch long hole
through 4140 PH, so I can make a barrel stub for my TC Contender.

From initial comments, I'll need carbide to do this... BUT... pure
carbide needs rigid setup, which I don't believe my Grizzly G9972Z lathe
has. Once I punch through a 1/2" hole, then I can whip out my CCMT
boring bar and do it.

Will HSS or cobalt drills get er done?

Heat treating would add more cost to this than it's worth. Really, if I
could find a clapped-out Contender barrel, I'd saw the barrel off, bore
it, and stub it. But barrels are not cheap on ebuy...

Some advise I got on this sort of thing matches well with my own
experience:

You can work hardened 4140 just fine with HSS or cobalt, because 4140
can't get all that hard (it's only 0.4% carbon, after all). But it dulls
the tools quickly.

For a _production_ environment, where floor space is money, and time is
money, and skilled help is money, and everything else is money, it makes
sense to own a superior machine and to use carbide, because you're not
spending money changing tools, or discarding parts that were made with
dull tools, or sharpening tools, or having a superior production monkey
working the machine who can exercise the right touch to make a superior
job with inferior tools.

But for a one-off in a hobby environment, just sharpen up a HSS or cobalt
drill just for this one time, use plenty of lubricant, and go for it.
You can take ten times as long to do the job and still be happy, and you
should be able to get a satisfactory result.

Then when you're done, sharpen the drill again.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

On Mon, 30 Jan 2012 11:51:27 -0600, Tim Wescott
wrote:

On Sun, 29 Jan 2012 20:37:15 -0600, Louis Ohland wrote:

Folks, I'm looking at boring a 5/8 inch diameter by 5 inch long hole
through 4140 PH, so I can make a barrel stub for my TC Contender.

From initial comments, I'll need carbide to do this... BUT... pure
carbide needs rigid setup, which I don't believe my Grizzly G9972Z lathe
has. Once I punch through a 1/2" hole, then I can whip out my CCMT
boring bar and do it.

Will HSS or cobalt drills get er done?

Heat treating would add more cost to this than it's worth. Really, if I
could find a clapped-out Contender barrel, I'd saw the barrel off, bore
it, and stub it. But barrels are not cheap on ebuy...

Some advise I got on this sort of thing matches well with my own
experience:

You can work hardened 4140 just fine with HSS or cobalt, because 4140
can't get all that hard (it's only 0.4% carbon, after all). But it dulls
the tools quickly.

A couple of points to avoid confusion: First, 4140 can be hardened up
to around Rc 57 - 59 -- quite hard. Second, that's because manganese
(or chromium) increases the hardenability of a low- or medium-alloy
steel with less carbon that would be required for a plain-carbon
steel.

While I'm at it, I realize that the pre-hardened form of 4140
frequently is called 4140 PH. But appending "PH" has meant
"precipitation-hardening" for many years, and using it that way for
"pre-hardened" can cause some confusion. 4140 does not
precipitation-harden.

I don't think there's an official standard for pre-hardened 4140, but
it's conventionally hardened to around Rc 28 - 32 when it's sold as
"pre-hardened."

--
Ed Huntress


For a _production_ environment, where floor space is money, and time is
money, and skilled help is money, and everything else is money, it makes
sense to own a superior machine and to use carbide, because you're not
spending money changing tools, or discarding parts that were made with
dull tools, or sharpening tools, or having a superior production monkey
working the machine who can exercise the right touch to make a superior
job with inferior tools.

But for a one-off in a hobby environment, just sharpen up a HSS or cobalt
drill just for this one time, use plenty of lubricant, and go for it.
You can take ten times as long to do the job and still be happy, and you
should be able to get a satisfactory result.

Then when you're done, sharpen the drill again.

On Jan 30, 10:26*am, Ed Huntress wrote:
On Mon, 30 Jan 2012 11:51:27 -0600, Tim Wescott





wrote:
On Sun, 29 Jan 2012 20:37:15 -0600, Louis Ohland wrote:

Folks, I'm looking at boring a 5/8 inch diameter by 5 inch long hole
through 4140 PH, so I can make a barrel stub for my TC Contender.

*From initial comments, I'll need carbide to do this... BUT... pure
carbide needs rigid setup, which I don't believe my Grizzly G9972Z lathe
has. Once I punch through a 1/2" hole, then I can whip out my CCMT
boring bar and do it.

Will HSS or cobalt drills get er done?

Heat treating would add more cost to this than it's worth. Really, if I
could find a clapped-out Contender barrel, I'd saw the barrel off, bore
it, and stub it. But barrels are not cheap on ebuy...

Some advise I got on this sort of thing matches well with my own
experience:

You can work hardened 4140 just fine with HSS or cobalt, because 4140
can't get all that hard (it's only 0.4% carbon, after all). *But it dulls
the tools quickly.

A couple of points to avoid confusion: First, 4140 can be hardened up
to around Rc 57 - 59 -- quite hard. Second, that's because manganese
(or chromium) increases the hardenability of a low- or medium-alloy
steel with less carbon that would be required for a plain-carbon
steel.

While I'm at it, I realize that the pre-hardened form of 4140
frequently is called 4140 PH. But appending "PH" has meant
"precipitation-hardening" for many years, and using it that way for
"pre-hardened" can cause some confusion. 4140 does not
precipitation-harden.

I don't think there's an official standard for pre-hardened 4140, but
it's conventionally hardened to around Rc 28 - 32 when it's sold as
"pre-hardened."

--
Ed Huntress





For a _production_ environment, where floor space is money, and time is
money, and skilled help is money, and everything else is money, it makes
sense to own a superior machine and to use carbide, because you're not
spending money changing tools, or discarding parts that were made with
dull tools, or sharpening tools, or having a superior production monkey
working the machine who can exercise the right touch to make a superior
job with inferior tools.

But for a one-off in a hobby environment, just sharpen up a HSS or cobalt
drill just for this one time, use plenty of lubricant, and go for it.
You can take ten times as long to do the job and still be happy, and you
should be able to get a satisfactory result.

Then when you're done, sharpen the drill again.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Few years ago a friend gave me about 100 lbs of 1.375 OD X 2.5 inch
4140 round stock. It was left over from a guy who didn't honor a
contract.

Machines realy nice with carbide and HSS lathe tooling and HSS drill
bits.