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[4]

Barrel Threading

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ddickey

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#1
A guy I made some 1/2-28 SS plugs for asked if I knew anything about barrel threading. I do not but know that the previous owner of my lathe did quite a bit pf gunsmithing. Probably why it came with a spider and also a spider chuck. Not sure. Watched a video or two.
Anyone have any experience in this? Tell me about it.
 

derf

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#2
What do you want to know? I've threaded 1000's of barrels.
 

TTD

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#3
I haven’t done 1000’s like @derf has, but have done quite a few airgun barrels. Not powder burners I know, but same principal applies.

Really no different than making threads for a common stud or bolt, except that for a barrel I normally place the barrel in my 4-jaw, lathe spider @ rear, appropriate size pin gauge in bore, then indicate off of pin gauge to ensure bore is perfectly centered with lathe axis. A lot of times the bore is not perfectly concentric with barrel o/d right from the factory, so you must do the steps above to ensure that whatever attachment you plan on threading on (airstripper, muzzle brake, suppressor where legal, etc) won’t clip the projectile upon leaving the barrel.

Just did this barrel the other day for a target pistol project I’m working on. .177cal, .590” o/d, 1/2” -20 threads on muzzle, 3/8”-24 threads @ breech end, 11 1/4” long.
m_Crosman MK II PFT Barrel 007.jpg
m_Crosman MK II PFT Barrel 006.jpg
m_Crosman MK II PFT Barrel 010.jpg
 
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ddickey

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#4
I only have two guns so not much of a gun guy but for some reason I was thinking the OD of the barrel had a taper. So I was wondering how you would hold it proper. The class of thread is 3? Looks nice. What is the material normally for a barrel?
 

derf

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#5
Typically the taper on a barrel starts after the thread tenon, which is cylindrical. Most gun barrels are made from 4140 CM, or 416R SS. I use a 6 jaw adjust-tru chuck, and either a spider or a reverse center on the outboard end.
After I spent many years single pointing threads, I purchased a geometric die head to do the barrels that were in high demand. With a geometric die head it only takes 2 passes for a finished thread, at 30 seconds a pass. It would normally take me 12-15 min to single point one.
Class 3 is a production standard, but some like them a little tighter depending on if it's a switch barrel or not.
To do this many barrels, I have 3 lathes set up for various operations. I use SB 13" for turning and threading, a Jet 1340 for chambering, and a SB heavy 10" set up with a belt sander for polishing.
 

Tozguy

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#6
With only one lathe I set up to do the threads and chambering in one set up through the headstock. The trick is to get both very concentric with the bore which is where the two spiders come in. There should be no problem holding on a slight taper with spiders. You should have the action when doing these operations to be able to do trial fits and set headspace.
Threading and chambering can also be done between centers.
It all depends on what the customer wants and what equipment you have.
 

Bobby Bailey

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#7
Posting in the Gunsmithing forum will get you more exposure.
At any rate, as others said, just ask the questions you have. Barrel work it one of the things we do for a living.
 
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