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Threading barrels

Rockchuck

Rockchuck

Silver $$ Contributor
Man waiting on my lathe has got me asking lots of questions. I guess iam just excited. Now here another guesting for you guys. What method do you use straight in with crossfeed or 29 1/2 deg compound method. What are the pro,s and cons of each. Also do any of you guy thread away from the chuck. Thanks

Ed
 
I use 29-1/2 degree compound except for the last few thousandths when I go with just the cross slide when threading towards the chuck. The reason for the 29-1/2 deg compound is to prevent the two chips from interfering with each other.

I use a dial indicator on the carriage to retract the cross slide at the same point on each pass. Right hand on the half nuts and left hand on the cross slide.
 
For a while I didn't have a threading dial and had to leave the half-nut engaged all the time. Only had to do a couple of barrels like that. Seems easy now in comparison.
 
I thread away from the chuck with upside down carbide insert threading tool inside/outside. Haven't seen any disadvantages only advantages. You need a chuck that isn't threaded on. I go straight in with cross slide for entire thread.
 
I thread toward the shoulder into a relief groove (except for sandwiched recoil lugs) all with the compound, set at 29-29.5 degrees. My threads look fine.

I set the carriage to zero at the spot where I want the threads to stop. I disengage the half nut at that spot. I find it more precise to watch the carriage dial to determine when to disengage than to watch the thread cutter on the barrel.

I highly recommend you go watch someone thread and chamber a barrel. There is so much you'll pick up.
 
At 60 rpm with a dial on the saddle you can pull out with the cross slide, no relief, and the thread looks like it was cut on a CNC lathe. It just takes coordination.

When I cut threads in aluminum at 300 rpm I thread away from the chuck.
 
It's no issue threading without a relief groove, and you really shouldn't do it on Remingtons and Christensens. However, most of the master machinists I know insist on a relief groove. I also have a customer whose spec requires a relief groove of a defined dimension on the muzzle.

So it's best to be able to go both ways on relief grooves....... ;)

As far as rechambering, I'd rather not........
 
INTJ said:
It's no issue threading without a relief groove, and you really shouldn't do it on Remingtons and Christensens. However, most of the master machinists I know insist on a relief groove. I also have a customer whose spec requires a relief groove of a defined dimension on the muzzle.

So it's best to be able to go both ways on relief grooves....... ;)

As far as rechambering, I'd rather not........
Click to expand...
Ive ran my reamer in too deep and had to bring the tenon forward a few times. A relief groove woulda messed that up
 
Dusty Stevens said:
Ive ran my reamer in too deep and had to bring the tenon forward a few times. A relief groove woulda messed that up
Click to expand...

Just to be totally transparent, and to show I am not hung up on how other guys do it; last week this exact scenario happened to me. The master machinist said to ALWAYS cut a relief groove. So I did. Then I got distracted and cut the chamber too deep--on a Christensen. I had to cut off the threads and start over. :oops:

My advice still remains--don't cut the chamber too deep...... :cool:
 
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INTJ said:
Just to be totally transparent, and to show I am not hung up on how other guys do it; last week this exact scenario happened to me. The master machinist said to ALWAYS cut a relief groove. So I did. Then I got distracted and cut the chamber too deep--on a Christensen. I had to cut off the threads and start over. :oops:

My advice still remains--don't cut the chamber too deep...... :cool:
Click to expand...
Everything is soooo simple.
 
INTJ said:
I also have a customer whose spec requires a relief groove of a defined dimension on the muzzle.
Click to expand...
Relief grooves serve another (probably more important) purpose other than a place to stop the tool.

Most muzzle devices simply have a chamfered starting thread. If you thread a muzzle without a relief groove, you'd better get really close to that shoulder or it's going to run out of thread and bind before it hits the shoulder. I've had to turn galled suppressor mounts off before because somebody else thought it looked cool to skip the thread relief.

You'll find a few devices with a counterbored female thread, but it's the exception, not the rule.

The same applies to actions with integral recoil lugs, although there is usually more wiggle room. It's not an issue with individual lugs because you can simply thread far enough that the lug covers your stopping point.
 
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The relief groove is the way to go especially when fitting suppressors.ive had to cut them off because they have ran out of thread and galled on.i fit lots of suppressors and quite a few different makes.Ksracer is 100% .with the relief cut you will hit your square shoulder and not have to worry if the suppressor manufacturer has relieved a thread or two..some of them don't.
 
Ok here we go, I am a master machinist. You swivel your compound rest over to 29 degrees, the reason for this is, as you advance the tool into the work, you will only be cutting on the front side of the tool. No pressure on the flank of the tool.
I cut a thread relief groove, to ensure a square shoulder & proper undercut, so the parts mate up .
 
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