Cutting a chamber

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AllenH59
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Cutting a chamber

Post by AllenH59 » Thu May 26, 2022 1:38 pm

Gentlemen:
My lathe is more than 26" through the headstock. how would you feel about cutting a chamber with the barrel in a collet and the chambered end supported by a steady rest? I cannot support the back end with a spider. I have not cut a chamber before. But I have a reamer, and would happily build or buy a floating reamer holder. Thanks. Allen

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GlennW
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Re: Cutting a chamber

Post by GlennW » Thu May 26, 2022 7:23 pm

Typically, the barrel bore is used as the reference, as the O.D. of the barrel may not be concentric with the bore.

If you have no way to set it up that way, you could check the barrel for concentricity first and you might get lucky!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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Bill Shields
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Re: Cutting a chamber

Post by Bill Shields » Thu May 26, 2022 9:30 pm

Why don't you chuck it up in a 4 jaw and indicate the bore?

You can (should) put a guide on the opposite end of the headstock to keep everything concentric?

I made a tap in ring with 4 screws like a 4 jaw chuck
Too many things going on to bother listing them.

AllenH59
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Re: Cutting a chamber

Post by AllenH59 » Fri May 27, 2022 12:32 am

Bill/Glenn. I am well stocked with work holding tools, an 8" and a 12" 4 jaw, and a 10" adjustable 3 jaw, which is my favorite, as well as a 5c collet chuck. Indicating on the bore is not an issue. What is an issue is supporting the end in the headstock, as a barrel would not reach through, especially with the added length of the chuck.

I have watched a bunch of videos, and have not seen anyone clambering who have to overcome this problem.

I thought about just letting the barrel protrude about a foot from the chuck, and indicating on the bore, and using a floating holder to cut the chamber, but of course with the cost of barrel blanks I want to have good confidence in my setup before I start making chips. I wonder if a floating reamer would make up for the error in this setup

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GlennW
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Re: Cutting a chamber

Post by GlennW » Fri May 27, 2022 5:20 am

AllenH59 wrote:
Thu May 26, 2022 1:38 pm
My lathe is more than 26" through the headstock. how would you feel about cutting a chamber with the barrel in a collet and the chambered end supported by a steady rest?
I'll clarify a bit more.

If you check both ends of the barrel, you may get lucky and they will both be concentric. If that is the case, you could chamber it as you describe buy dialing the chuck end in by the OD and support the chamber end using the steady. Do not grip the barrel using the full length of the jaws though.

If it is a barrel blank, can you turn the OD concentric for a short length on each end to accomplish the above? (when you say "barrel blank" I envision round bar that had been drilled and rifled)

You could also use a center in the headstock and a drive dog to turn the barrel, but that takes a bit of an odd setup to keep the barrel against the center.

None of this is really ideal but if it's the only way you have to do it...
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

Rolland
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Re: Cutting a chamber

Post by Rolland » Sun Jun 05, 2022 6:35 pm

Sounds like your best method is to set the barrel muzzle end in a collet and support the chamber end in a steady rest and indicate on the bore. The use of a floating chamber reamer holder would be the best way to cut the chamber. It will depend on the lenght of the bed as to how deep you set the barrel in the collet. since the barrel is tapered there will be a certain amount of movement in the collet as it will grip only on a small portion of the barrel. but that should give you enough movement to center on the steady rest and still drive the barrel. I have done a few that way when the barrel is too short to go all the way through the head stock. There are a number of books on amazon that would help you if you have never cut a chamber. Manson reamers makes an excellent floating reamer holder its the one I use.

Harold_V
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Re: Cutting a chamber

Post by Harold_V » Mon Jun 06, 2022 3:44 pm

Rolland wrote:
Sun Jun 05, 2022 6:35 pm
end in a steady rest and indicate on the bore.
It's not clear to me what benefit that would have. A steady does not allow for any adjustment in concentricity of the bore to the exterior of a barrel, and it is not capable of determining when the bore is on center. What am I missing?

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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Bill Shields
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Re: Cutting a chamber

Post by Bill Shields » Mon Jun 06, 2022 4:00 pm

ditto.....
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earlgo
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Re: Cutting a chamber

Post by earlgo » Tue Jun 07, 2022 2:37 pm

I'm sure you fellows have this all figured out and done, but....
When I was at the Colorado School of Trades, this is a method that was taught.
First one used the bore centering cutter which is a 60° cutter with a pilot to fit the bore.
BORE CENTERING CUTTER small.jpg

Then we set the barrel up between centers with a drive dog and faceplate. The muzzle end at the faceplate. The drive dog was tied to the faceplate by a nylon cord. BUT the faceplate was unscrewed a couple of turns so that after the cord was tight, the faceplate was then screwed home, thus tightening the attachment.
Then this spider was secured near the chamber end but located so that a steady rest could be used to thread or chamber or both.
BARREL CHAMBERING SPIDER.jpg
Before any machining was done on the barrel itself the surface of the spider was machined concentric with the bore. This made the barrel rotate about the bore axis and not the barrel surface.
Then chambering and/or threading could be done concentrically with the bore.
After the machine work and chambering was done, the muzzle end was recrowned to remove any burrs or chamfer caused by the centering cutter.
I learned a lot there.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

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rmac
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Re: Cutting a chamber

Post by rmac » Tue Jun 07, 2022 3:36 pm

earlgo wrote: Before any machining was done on the barrel itself the surface of the spider was machined concentric with the bore.
Clever!

earlgo
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Re: Cutting a chamber

Post by earlgo » Thu Jun 23, 2022 1:42 pm

I was looking for something else and finally found this. That is why I showed a 3D model instead of this elusive spider. :lol:
spider for chambering.jpg
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

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