barrel threading

[skizzums]

hey guys, tomorrow I am going to tackle something I haven't yet done before. it doesn't seem like an overly complicated job, just wanna make sure that I am not missing something. I am going to be threading the barrel of my finn mosin and adding a brake. I had a press fitted brake before, and those never ork out. so I ordered the die and already have the tapping tools. my barrel will not fit on my newer "smithy" mill/lathe, so I will be using my old "atlas" lathe to chuck the barrel into and working from there. I am using a generic brake and milling it down to a thinner profile, making the three ports into one large port and one small to further decrease weight and tapering down the bottom edge to be somewhat flush with the barrel and tapering and recessing the crown of te brake as well, that's the easy and fun stuff of course. and hopefully making it unique and cool looking in the process.

question is, how to square up the threading to the barrel. should I just be squaring off the top of the barrel and then threading as I would anything else? or should I machine a piece of bar to fit into my bore and use the bore to center the threading.....? and how would I go about doing that, if its the right way? I have no issues with just squaring the barrel head and then threading and increasing the size of exit hole of needed, but will that effect accuracy?

just give me some pointers on the RIGHT way to thread my barrel. only wanna do this once, obviously. I would like to hear from tobnpr and Dixie if ya'lls is available, and of course anyone else that may have some useful info.

thanks guys

raw brake that will be "customized" or at least "bubba'd"

 

[Clark]

10 years ago my friend died of a heart attack while hunting.
His widow wanted me to have his 1938 Atlas Craftsman lathe 101.07402 12x36 deluxe with Timken tapered roller bearings 1939 tailstock.
He had Boeing fellowship [high stress] and was a few months from retiring.
I did barrel an M70 on it and shot deer.

But my video showing how to thread a muzzle is on my Chinese 12x36 lathe.

https://www.youtube.com/watch?v=m-JhnjgtxQw

 

[Gunplummer]

I would take a gage pin or turn a piece of stock to indicate off the bore. I have seen some really out of wack military barrels. Not a bad video, but if you never cut a metric thread on a manual lathe , it will get you in trouble. Does the brake have a metric thread?

 

[skizzums]

It is a 5/8x24, the barrel is cut on the lathe with a 12 degree crown. Thank you Clark for the vid. I just got to work and haven't watched it, but will shortly.

I agree that turning a bar to go into the bore as a guide seems like the best route, but ill check your vid

 

[punkinhead]

If you're not comfortable single point threading and are dead set on using a die, at least single point the threads deep enough for your die to follow them and finish with the die. Otherwise odds are high that the die will get cocked and produce threads that aren't square to your bore.

 

[tobnpr]

I guess I need another cup of coffee, it's still early...

so I ordered the die and already have the tapping tools. my barrel will not fit on my newer "smithy" mill/lathe, so I will be using my old "atlas" lathe to chuck the barrel into and working from there.

I'm a bit confused. You're going to use a die, rather than turning the barrel on the (Atlas) lathe- to cut the threads? And what are the tapping tools for?

 

[Clark]

Here is a short video I made about dialing in the barrel
https://www.youtube.com/watch?v=9hQX8OQbwvQ

 

[skizzums]

yes, i was just planning to use the lathe as a tool to keep the barrel square while using the tapping die. not turning in the motor, just trueing into the chuck so i can hand turn it straight. but these are just assumptions, as i said, i havent threaded anything before.

my main concern is, should i make sure the barrel cut is perfect 90 degree and thread to the barrel, or machine a tool to thread straight to the bore?

clark, i just watched your vids. i understand how to dal in the bbarrel correctly, but i don't think i am experienced enough yet to cut perfect threads with the old lthe yet, plus its missing lots of parts. i could probbly precise threding on the smith lathe, bt not hte old atlas, still figuring that old thing out and just have boxes of "stuff" that i havent quite figured out how to use yet.

so is there anything wrong with dialing the barrel in the 4 jaw, and hand turning with a die after shaving off the correct amount of materieal for the die? or am i totally misunderstanding this?

maybe i am not explaining what i am trying to do correctly, i will post up a pic of my "plan" on the lathe to better communicate what i am trying to do. but question still stands, do i wnt suare to the barrel or true to the bore, or does it really matter?

my experience with the atlas has simply been barrel cutting, turning off sight bases and doing crowns. aafter i get the brake on, one way or the other, i then plan to turn the brake while on the barrel to closely match the barrel profile, or at lest attempt.

 

[Gunplummer]

I think punkinhead has a point about starting the thread with the lathe. Barrel steel is hard on good dies. Why not practice on a piece of junk steel? You will never learn to cut a thread unless you try it.

 

[Jimro]

so is there anything wrong with dialing the barrel in the 4 jaw, and hand turning with a die after shaving off the correct amount of materieal for the die? or am i totally misunderstanding this?

Nothing wrong with that at all.

Turn a bore indicator out of brass or aluminum to align the barrel in your 4 jaw, then shave your barrel down to where the die will work. Don't forget to cut a relief area for the threads.

In the end you should have a muzzle break that is true to bore.

Jimro

 

[Clark]

I agree with Gunplumber.
Practice cutting threads on plastic pipe and work your way up in hardness.

The hole in the spindle may be too small for the breech to fit.
You may need to put the barrel in the steady rest.

I don't have much for pics, but here is one of my Atlas with a barrel in it before I gave that lathe away.

 

[punkinhead]

yes, i was just planning to use the lathe as a tool to keep the barrel square while using the tapping die.

You'd think that would work, but it generally doesn't. The die will more than likely get started crooked. Single point the threads or take it to someone who can. It's surprisingly cheap to have a barrel threaded.

 

[tobnpr]

OK...
So now I understand what you're after- I think.
I'll preface my remarks by stating you've already heard from guys with much more machining knowledge than I ( I bug Clark for his opinion from time to time ), but I'll tell you what I would probably do...

First, you didn't say whether you were going to remove the barrel from the action. Not an easy task, I've seen Clark's video where he does it with a ten foot cheater and a forklift pressing down on the end....not quite, but you get the idea.

It's a Finn, so it might not be as bad. I suppose you could put witness marks on the barrel and receiver, pull the barrel, re-torque to the index marks after you've done the barrel work and of course check headspace after.

If you're not pulling the barrel, what's your plan? I don't know any way to turn the barrel on the receiver without a cat's head/receiver fixture to hold it, a bushing over the barrel in a steady close to the muzzle- with the muzzle in a live center. But like I said- that's above my pay grade and I'm sure there may be other ways.

If you do pull the barrel...
Do you have a spider outboard the spindle to work through the spindle bore?
Or are you going to do it similar to above (but without needing the receiver fixture)?

Moving on...
Depending on how close your barrel OD is to what you need...

and hand turning with a die after shaving off the correct amount of materieal for the die?

I have seen a number of hobbyists use equipment from the company I'm going to link below to do all of this work by hand. From what I've seen, you can produce acceptable work. Not match/precision quality by any means- but it might be worth a try. Hell, I might try it myself just to see how well it works. MN's are notorious for having their bores not being concentric to the barrel- but with a Finn barrel, I don't think that's going to be an issue.

If the barrel OD is somewhat close to what you need, you can start with an "oversize" die, shave the threads off, re-cut with the next size die, shave the threads off, until you get to the major diameter of .616- .623 that you need for the 5/8" x 24t die. Or, you could use their piloted annular cutter which is capable of removing a lot more material, much faster, this is the one for 5/8":

http://www.cncwarrior.com/0-62-Annular-Cutter-Kit-p/25763.htm

I'll leave you to digest all this, major thing being they do make piloted dies- which should keep you square "enough". I'd like to see Dave Manson make something along these lines. His piloted muzzle crowning tools produce very nice results- showing that quality piloted hand tools can get the job done without a lathe. If a crown can be cut, I see no reason a barrel can't be threaded to acceptable standards. Again, you're not building a precision rifle here.

Start with the DIY instructions, very well put together:
http://www.cncwarrior.com/v/vspfiles/Barrel_Threading.pdf

Then the rest of the "stuff", here:

http://www.cncwarrior.com/category-s/1851.htm


Hope this helps, JMO, YMMV...

 

[Clark]

If you think unguided taps make a messy set of threads, dies are worse.
Dies and taps work well freehand at cleaning up existing threads or extending them, but my results are often poor at making new threads. I do it a lot with a tap in an electric drill into a cheap part. But barrels are not cheap, especially after you have some hours investing in them.

 

[Gunplummer]

Absolutely. One would not think a die could cut off center, but it will. I have had good luck with small dies by making a die holder with a hollow shank and putting the shank in the tailstock drill chuck. (If you can trust the center height of the tailstock). I put the chuck in neutral, turn it by hand, and keep pressure on the die with the tailstock handwheel, or keep the tailstock loose and push against the whole tailstock. Works OK for a handful of small screws, but I would not make a habit out of it. Best to learn the correct way. Any lathe is better than none.

 

[tobnpr]

^^
No one could disagree that unguided dies would be a mistake.
But the ones I linked are piloted- and Dave Manson has proven that a piloted system can get the job done. Used by a lot of gunsmiths (and I have a set on order). It's not a quality system like Manson's- but for the likes of Mosin-Nagants and AK's, I do believe they could produce acceptable results when used by a capable set of hands.

 

[skizzums]

Awesome links to the CNCwarrior sites. Thank you, very helpful. Fathers day was a mess for me, ending up having to grill steaks for about 9 in-laws in the mere 95degrre sun. So, no playing yesterday. Will get to it this week for sure. I'm just going to grab some cut off Harrell stock and practice getting my hands dirty with the threading. I'll get er done one way or the other, my dad is back in town and he knows how to work the lathe, mostly. I'll will update this thread when I get to it and have a pretty brake, or I fail and have to lose another inch of barrel. Thanks for the discussion, has been very helpful.

 

[Clark]

I was cutting threads today.

 

[Gunfixr]

I thread quite a few barrels.
The only time i have ever used a die is on an ak, being left hand metric, and a bit of a pita to set up, and run so close to the quite tall front sight. I use a pilot, before doing the job, make sure of the barrel od, and turn it to size if needed.
But, this is only for flash hiders.
I ask, multiple times, to be sure. If there is any thoughts or hesitation suggesting a muzzle brake or suppressor is going on the muzzle, i single point the threads in the lathe, never mind the extra work.
All others are single pointed as a matter of course.

One suggestion, however. You should have two points of reference for setting up in the lathe. You need to be able to not only determine that the barrel is centered, but straight. Either a center in the tailstock, if your tailstock is on, a steady rest, both ends of the spindle if your lathe can do that. If a center in the tailstock, use something between the hardened center, and the muzzle, or you will damage the crown. If you are crowning after, doesnt matter. A crowning tool will never do the job as well as lathe crowning.