My winter (shop season) project is to teach myself how to chamber a rifle barrel.

Background: I have two lathes, a 12x36 Tiawainese Gearhead with 1-5/8" spindle bore that I bought new and a cherry 1949 SB Model A with 4' ways and about every attachment ever made for it except a 3C collet closer that my Dad bought new. I really like that little SB, I helped clean the cosmolene off it when it arrived in the basement as a new lathe a few months before my 7th birthday. I've been using a lathe on a hobby basis since I was 10.

I also did searches, found and read everything I can find on this terrific forum on chambering. I even copied the good posts and pasted them into an MS-WORD file so I could study them on paper. And I've ordered, but not yet received, "Complete Illsutrated Guide to Rifle Barrel Fitting" from Precision Shooting Website. I'll read it before I cut the first chip. OK, with that background:

I think I understand the alignment problem, which is two fold:

First is to align the centerline of the section of bore where the chamber will be cut with the centerline of spindle rotation. This being complicated by the fact that the bore centerline may NOT be aligned with the centerline of the barrel OD in that reigon within the tolerances that would be desired.

Second is to align the reamer with the bore/spindle centerline so that it doesn't cut an oversize chamber. This might be done with a good floating reamer holder.

I'd prefer to do my chamber cutting in the spindle of the 12x36 lathe. I can make a cathead (?) to go on the other end easily enough to support the end of the barrel that isn't in the chuck.

The post that got my attention was the one pointing out that, because my 4J (or any 4J I've ever seen for that matter) has such long jaws adjusting the support screws on the far end of the spindle won't do anything but bend the barrel, they will, at least in theory, have nothing to do with where the bore section is pointed because that will be controlled by the jaws of the chuck.

OK, I was thinking about this and it occurred to me there might be a simple solution to this problem. Imagine a collar clamped around the breech that is in reality a 3/4" thick (along the axis of the bore) section taken from the center of a sphere. In other words, the OD of the collar is radiused in section view to match it's diameter. Just to be clear, the OD surface of the collar would look like the OD of a self aligning bearing, and would in fact allow the barrel in the chuck to be clamped with out bending regardless of the position of the muzzle end in the cathead on the other end of the spindle.

That being the case, if one needed to change the angle of the bore, if the chuck jaws were loosened but still in light contact, the cathead bolts could be adjusted the chuck jaws retightened, and there would be no bending force on the barrel because the jaws would just tighten on a slightly different part of the spherical suface section on the collar OD.

Making such a collar wouldn't be hard to do. It could even be threaded internally to match the barrel threads with a saw cut in one side so that a recessed clamping screw could be used to tighten it non distructivelyl on the barrel threads.

OK, am I nuts, or will this work to eliminate bending stress on the barrel?

Fitch

This post may be worth a few thousand words. Lots of pics help explain things!

https://forums.accuratereloading.com/eve/forums/a/tpc/f/...=427103958#427103958

James has a great setup and the copper wire works. On mine to shorten the distance in the headstock, I have a cathead instead of a chuck.That means that I have 2 catheads. I use 4 setscrews that are 1/2x20tpi with copper inserts in them.
Butch

[QUOTE]Originally posted by gunmaker:
This post may be worth a few thousand words. Lots of pics help explain things! [QUOTE]

Thank you sir. That outstanding post answered questions I didn't know enough to ask. Well done.

Fitch

Fitch,
I suggest purchasing Darrel Holland's excellent video on the subject. I got mine via AGI, American Gunsmithing Institute about ten years ago when I was getting ready to build my first custom Mauser. He is extremely thorough and explains every detail, in detail. You can search AGI or check the usual publications for ads. Available CD or tape. While I started machining a little later in life than you, I had no problems and got a real shooter in the end.
Mike
Mike

Thanks Mike, I'll look for it.

Fitch