Turning barrels on a lathe

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Fixit

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I was doing some work on a friends lathe last night, shortening a 30" barrel down to 18.5+" long.

i was having some issues with chatter once i had parted the barrel and no longer had the live end trueing things up.

its done now, looks ok except for a tooling mark on the top side of the barrel, but....

whats the right way to do this on a lathe??? My biggest issue was that the barrel wasnt concentric to the bore, and the fact that it is tapered end to end so the jaws dont self align very well.



any pointers?
 
12" ish. woulda been closer but the barrel has the mag tube ring that secures the barrel to the gun in the way, and the muzzle side wasnt long enough to stick through the chuck tube.


i was suprised to find out that the barrel wasnt the same thickness all the way around too.
 
can you put it between centers and turn down the end square to the bore , then zero it out on a 4 jaw chuck and recut the end ?

then put it back bewteen centers and clean up the area that is square to the bore and blend it into the rest of the barrel ?
 
between centers would have been nice, but you cant "crown" the shotgun barrel when the live center is in the way... unless theres a trick i dont know about?
 
Off center bores are not unusual, either on rifles or shotguns.
I'm surprised that you didn't have an interesting experience parting off with the center supporting the cut off piece.
Trying to crown a barrel with 12" of it projecting beyond the chuck isn't exactly an optimal method. Using a steady would make a big difference.
 
You shouldn't be chucking it in the jaws, you should be turning it between centers with a lathe dog...

Rough cut it to length with a bandsaw, then put the chamber on a dead center/lathe dog (wrap the barrel with shim stock or aluminum foil to prevent the lock screw on the dog marring the barrel). Use a live center (preferably) on the muzzle end, but a dead center doesn't hurt too badly since you'll be crowning later. Turn your profile as desired. If the tailstock is properly aligned, you'll have a concentric profile.

To crown it, chuck it up as best you can (indicating against the bore, not the outside surface); a 4-jaw chuck and a 4-point jig to support the back end will make this easier. Leave as little barrel stickout as you can (less than 3 diameters is a good guideline). Turn it slowly, and cut the crown. Then polish with finer and finer abrasives to remove burrs.

The actual cutting, I find, takes little time when I do lathe work... it's the setup that takes about 90% of the machining time for a precision piece IMO.

-M
 
Also, if the 'shank' on the bore is round and concentric, you can just chuck that part up and use a steady rest to support the muzzle end for crowning.

Indicate against the bore.

-M
 
Sorry for a slightly off-topic question, but i figured somebody here would answer me without having to start a new thread.

I need to shorten and thread (for flash hider) a barrel on a rifle. The barrel is 21", and i need to shorten it to 18.5". Removing the barrel from the receiver is not an option (long story).
Is 18.5" long enough to be inserted through the "chunk and gear case" with the receiver still attached to it? Please excuse the improper terminology. I do realize that this will vary on different lathes. What is the proper name for the combined length of the channel through the chunk and gearcase (so i can ask my gunsmith if his lathe is small enough)?
Thanks!
 
zZ_denis said:
Sorry for a slightly off-topic question, but i figured somebody here would answer me without having to start a new thread.

I need to shorten and thread (for flash hider) a barrel on a rifle. The barrel is 21", and i need to shorten it to 18.5". Removing the barrel from the receiver is not an option (long story).
Is 18.5" long enough to be inserted through the "chunk and gear case" with the receiver still attached to it? Please excuse the improper terminology. I do realize that this will vary on different lathes. What is the proper name for the combined length of the channel through the chunk and gearcase (so i can ask my gunsmith if his lathe is small enough)?
Thanks!
Click to expand...

The headstock, chuck, and the spindle through-hole. Or the spindle bore.

-M
 
ZZ what you are describing is the hole through the headstock. I would think you would need a fairly large lathe for the headstock to be bored to somewhere around 1" or greater. The concern about having the receiver sticking out behind the gearbox is that it will probably not be balanced and lead to vibration. You would probably want to turn at a pretty slow speed.
Also surprised that there was only one reference to a steady rest in the original question. If the barrel is not round as in having a ventilated rib, make up a plastic bushing to fit snugly around the barrel, turn the barrel between centers to make the outside of the bushing round and concentric to the bore, then support the barrel in the steady rest using the bushing. You can probably buy a relatively small chunk of 1" thick nylon at your local plastic shop, to make the bushing from.

cheers mooncoon
 
mooncoon said:
ZZ what you are describing is the hole through the headstock. I would think you would need a fairly large lathe for the headstock to be bored to somewhere around 1" or greater.
Click to expand...

i think the only one inch bore ive seen lately is on those hobby lathes, most gun smiths should have a lathe with a 2.5" bore or bigger.

the smallest ive run in recent memory has a 3.875 bore
 
iconfig said:
i think the only one inch bore ive seen lately is on those hobby lathes, most gun smiths should have a lathe with a 2.5" bore or bigger.

the smallest ive run in recent memory has a 3.875 bore
Click to expand...

I've got an 11x27" that I bought for mucking about, and it's got a 1.5" through-bore.

Definitely not hard to find a 1" bore in a machinist/gunsmith's shop.

-M
 
When hanging a lot of length out the back side of the headstock, a "cat head" or "spider" becomes a life saver. It's a simple piece of pipe that attaches to the backside of the spindle bore. It then has 3 or 4 bolts evenly spaced to allow you to steady up parts hanging out the backside of the head stock. It's like a mini steady rest.

Another option is a plastic bushing tapped into the end. I used those mostly for the CNC lathe when running long bars through the headstock to make multiple parts. You can buy then pre-made in standard sizes, even non-round shapes. They call them silent tubes or spindle liners. Work best when running a bar puller on the turret as they hold the bar stock fairly centered when the jaws are un-clamped.
 
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iconfig said:
i think the only one inch bore ive seen lately is on those hobby lathes, most gun smiths should have a lathe with a 2.5" bore or bigger.

the smallest ive run in recent memory has a 3.875 bore
Click to expand...

:eek: My lathe weighs 1600lbs, has a 3hp motor, 40" centers and a 1 1/2" spindle bore. And here I thought it was a decent size for gunsmithing.
 
I'v adopt the following method for working barrels. The copper/malleable metal ring prevents marring and can lamp on to a tapered barrel. With a spyder on the other end of the headstock, I can dial in on the bore with indicator rods. Also, with this method i can do muzzle work with the barrel on the action - as long as the barrel is over 20"

IMG_0068.JPG

barrelthread2.jpg
 
Thanks for all the responses, guys!

So what is the length of the headstock hole on an averege lathe? Is it short enough to accomodate an 18.5" barrel (so that it sticks out at least a little from the chuck)?
Previous poster said that he can do muzzle work on barrels as long as theyre 20"+, but his lathe seems huge (to me atelast).
 
zZ_denis said:
Previous poster said that he can do muzzle work on barrels as long as theyre 20"+, but his lathe seems huge (to me atelast).
Click to expand...

Looks tiny, I use one with a 3inch bore (smallest I have access to), and the plus side is you can do it with a reciever attached. I would suggest talking to whoever is doing the work and seeing what they have and can do. If the reciever stays on you still may want to remover rings, bases, trigger group etc.
 
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