Threading rifle barrels

JW Machine · Mar 11, 2007

I am not new to machining, but now have some gunsmithing work for the first time and would appreciate some advice.

I need to thread the ends of some new barrels to fit them into receivers. I am planning to indicate off the bore for this, chucking on the cylindrical portion of the barrel just ahead of the receiver, as the rest of its length is tapered.

My question is this: Is the barrel OD parallel enough to the bore for this to be accurate? I know they are not necessarily coaxial, but I can adjust for this with my chuck. However, if they are not parallel, I think I will need to find a new way to indicate or hold the barrel to make sure the threads are both parallel and coaxial with the bore.

As I said, I am new to gunsmithing. Is this a valid concern, or am I attempting to achieve an unnecessary level of accuracy?

trevj · Mar 11, 2007

Do a web search for "cat's head chuck" or "Cat head chuck"

Essentially it is a set of four screws that are used very much like a four jaw chuck. Then picture one on the back end of the lathe spindle.

With one of those on the back of the spindle, and the breech end in a 4 jaw chuck, one then spends a great deal of time dialing everything to dead nuts zero.
Then thread it.
There is no guaruntee that the bore is truly concentric with the outside. Hopefully it is close, but that depends, among other things, on whether the guy that profiled the barrel was setting up carefully, and what tolerances he was working to. You can use a long precisely fitted pin in the bore to indicate off, but you will need some sensitive indicators, as well as an accurately fitted pin for it to be worth the effort.

Best bet, is to get a few decent books, videos, or other information that will show you the what's and the why's. Esp. the why's.

I am not about to suggest that the work is beyond you, just that you should be clear on how to setup and why, before you cut metal and risk your part.

Cheers
Trevor Jones

Rustystud · Mar 12, 2007

JW Machine:

I would never use a 3 jaw chuck in any part of turning, threading, or chambering a rifle barrel.
It just is not accurate enough. Take a look at Greg Tannels (Gretan) or Mike Bryants BryantsCustomguns) web sites.
Rustystud

JW Machine · Mar 12, 2007

Thanks for the replies so far.

Yes, you may assume that I am only threading them and not doing any chambering. I am doing the work for a gunsmith who will chamber them later but lacks the ability to cut metric threads with his lathe.

Rustystud · Mar 12, 2007

JW Machine:

For accuracy one should dial in within .0002, turn, thread, and chamber all in same set-up.

Never part off a barrel. Induces too much stress cut all barrels in a band saw with coolant.

Only use single point tooling and/or piloted tooling.

Four, six jaw independent set chucks or a collet are required for barrel work.

I recomend a floating reamer holder also.

Rustystud

clint campbell · Mar 12, 2007

Cant you get the gunsmith to come in and set up to his specs. That way our covered and its back on him. If hes threading semi auto lead hose barrels (metric threads makes this a possibilty)its just not as critical. Good luck. clint

peterh5322 · Mar 12, 2007

"I would never use a 3 jaw chuck in any part of turning, threading, or chambering a rifle barrel."

How about a high-quality "Set True" 3-jaw scroll chuck?

abarnsley · Mar 12, 2007

peterh5322
I work on many barrels that are not round (have bottom lugs or such, 3 jaws are worthless for those. I would rather be making chips than changing chucks back and forth. Instead of a Set True 3 jaw that must be set like a 4 jaw to get into tenths runout, how about just using a 4 Jaw? its faster, (on varying diameter work) has better grip and a decent cheap one can be set up to turn truer than a Set True. If everything was same Diameter, round or hex, Set True MIGHT save time, but not much of that in gunsmithing...

Yankee Metallic · Mar 16, 2007

Turn the gun between centers to do the threading. This is even easier if the barrel is not chambered already and not attached to a rifle. Barrel wall thickness varies up to .004" from center. Use a 6 jaw set true, or 4 jaw independent, and support the chambered end so it isn't flopping around. If you are new to this, practice your setups on old barrels or material blanks. DOuble check the threads on the muzzle brakes. If you have to 'TIME' the threads to brake is facing a certain direction when fully threaded, cut it tight so it is just short of meetng it's timed position. Screw & unscrew the brake several times and the threads will settle down/ break in so the timing will be right.

ThomD · Mar 28, 2007

Try these also:

http://www.gunshowbooks.com/cgi-bin/webc.exe/st_prod.html?p_prodid=GS365419&sid=9a1Ux7zh

http://www.gunshowbooks.com/cgi-bin/webc.exe/st_prod.html?p_prodid=GS355419&sid=9a1Ux7zh

BATF666 · Mar 29, 2007

I will vouch for the first book in the above link..It has been a very good instructional book with many ideas and illustrations.
I am not familiar with the second one.

Now I assume your going through your headstock on the lathe or are you doing it from a chuck and a tail stock.

jabezkin · Mar 29, 2007

Between centers,thru the head,collet(very good),3 jaw, 3 jaw adjustable, 4 jaw, 4 jaw universal, they all depend on the machine and the skill of the operator. Oh, 2 jaw, 6 jaw and soft jaws. Each has some advantage, none are THE BEST.
Say what you like about each way, and what you don't.
Exchange ideas to improve.

lathefan · Mar 31, 2007

"I would never use a 3 jaw chuck in any part of turning, threading, or chambering a rifle barrel."

...if all you have is a 3 jaw...chuck a piece of stock in it and turn a 60 degree point on it (soft center), then work between centers.

jabezkin · Mar 31, 2007

lathefan: ZACKLY WHAT I MEAN1

Search

Largest Manufacturing Technology Community on the Web

Search

Threading rifle barrels

JW Machine

Aluminum

trevj

Titanium

Rustystud

Guest

JW Machine

Aluminum

Rustystud

Guest

clint campbell

Plastic

peterh5322

Diamond

abarnsley

Titanium

Yankee Metallic

Hot Rolled

ThomD

Aluminum

BATF666

Plastic

jabezkin

Stainless

lathefan

Titanium

jabezkin

Stainless

Similar threads