Home Forums Hunting & Shooting Gunsmithing Muzzle Threading

I want to thread the muzzle on my son's H&R 17 HMR barrel for a suppressor. The spindle bore of my lathe is too small to fit neither the lug end of the barrel in it nor will the forend stud fit through. I have considered threading it between centers with a small aluminum plug fitted for the bore that gives enough offset from my live center to cut threads all the way to the end. But...how do I indicate from the bore? I don't trust the outside of the barrel is concentric nor do I trust that the bore was cut perfectly center.

Any advice is appreciated.

Where would that go? My live center has to rest on the bore plug to hold the barrel.

You wanted to center everything up on the bore right?

Yes but I'm not sure how to do that without the live center supporting the end of the barrel. My barrel won't fit inside the spindle bore.

Maybe you could get a 1/2x28 die and somehow make a fixture to allow it to be dead ass straight with the bore. I can picture what would need to be done but I struggle to find the words to describe what would work.

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We need some Smyth Busting here...

One way or another, I'm using my lathe. I'm fairly certain the lathe can be used to start a die straight much like using a mill to keep a die straight, but I would prefer to not use a die.

Do you have a way to center up the die with the tailstock? Square it up with the barrel?

The die?

Use a brass "crown saver" from Brownells on the live center. Swing the barrel between centers on your lathe. Cut the muzzle end to 1/2". Because you are between centers, the cut will be concentric with the bore. Thread in the usual way. I often run a die over the completed threads to smooth them up.

Why not put it in a steady rest, then check with a dial indicator off of a brass rod in the bore to see if it's concentric. Thread as usual if it's good.

That may work. I have a steady rest but I hate using it on a finished barrel for a few reasons. One, it's been a bear to indicate a barrel in perfectly round. Two, the brass contacts have left marks on the barrel. Tonight I have learned a few ways to improve upon both of those issues and it's time to try again using better techinques.

My old lathe only has a 1" bore headstock. I know your pain.LOL

Maybe put one of THESE in the tailstock.

I'll get one. I can see using it on something.

I make a nylon plug to protect the crown. Either that, or true up the crown after threading. GD

You have to cut a shoulder first, then thread it while indicating on the bore centerline.
You don't want to trash your suppressor because of Bubba-ed muzzle threads.

I always thread with the live center, after making my major diameter cut for threading to length. The crown is the least of my worries as It gets easily touched up with a brass ball or slotted round head wood screw with VG compound on it, but if done properly , the live center doesn't hurt the crown , as my live center is softer than the barrel. Centering the chamber in the headstock can be a challenge depending on the barrel , sometimes that takes a solid center and a lathe dog clamp to get that , or a machined "chamber rod" sized to allow a barrel with a rear welded mount to ride between jaws and a small hard wood wedge to keep out any backlash. I have used my steady rest WITHOUT contact 1/4 of the way back from the muzzle, then to check threads or run a die, run the rest contacts up to the barrel for support, back the tailstock off to check, reinsert tailstock , lower the steady rest contacts and continue as necessary. You wont mar the barrel finish this way.
Rich

I use a half dead center. Gives enough room to do it. Centers on your bore.

carbide tipped half dead center

You can get them on ebay fairly reasonable

I use a dead center to center the bore of the gun. Then, I use live centers for turning the OD to the major diameter & keeping the tap/die straight with the piece while keeping the tailpiece tensioned well enough to hold the tool straight.

It's generally easier for me than taking the lathe apart and changing gears on my small lathe.

Though anyone will admit that single point threading is better.

Someone makes a spring loaded center tool so you don't have to constantly be turning the tailstock in every half turn or so.

I'll also add, you don't have to use the tool the entire depth of the thread either. Once you have it about a 1/4 threaded, it's as straight (or crooked) as it's going to be.

I read it twice...but I must be missing something here...maybe I'm missing a lot here. Remove chuck install Dead center in spindle bore on the breech end, lathe dog, live center in muzzle, single point the thread....done. Die is a recipe for non alignment and non concentricity..and what is with the half center?...do you need to recut the muzzle face? I must have missed something.

Your single point cutter goods will contact your live center goods, iirc.


Dinny,

Did similar to this lately on a barreled action. Muzzle on a live center. Turned down muzzle diameter a ways just for tool clearance. It was less than thread minor. Then threaded back from there. Then cut to length and did the crown with my Manson hand tool. All I could think of at the time. It worked but I had the extra barrel length and the Manson 11° tool.

Half dead center... Hmmm....

We are just cutting a simple male thread on the muzzle for a can or a brake...right? Why in hell would the 60 deg single point threading tool bit even get within a 100 thou wall thickness of the bore where the live center is seated? Am I going nuts? Is this something other than the simplest of operations...cutting external threads between centers?

LOL

Not the cutter's business end hitting the center - inside the bore. It's "side" hits the center outside. When the angle of the dangle conflicts with the doodad - you see?


Maybe he, like I, was using an indexable tool... Whereas you picture a straight HSS tool?

LOL


FL,

This type of a setup would work, I figure you mean this....

But my external thread cutter, with a three-tipped insert was positioned where the tool would contact the center, before reaching the work....

My tool is like this. I can see where having a petite HSS threading tool would be better here.


A long (extended) nose live center would help.


Or a half dead center as suggested.

A 1/4" or 5/16" 60 degree v thread cutting tool is cheap , or you can grind one from HSS bar stock. The Insert type holders are too big for close in work near a Live center.

Exactly correct Moose...what Mtn Boomer should be doing is the old skool setup shown in the upper page here...except the 1/4" 60 deg threading point should be mounted upside down, the lathe run in reverse and cut the threads AWAY from the inner shoulder TOWARD the muzzle. Thereby avoiding a crash and also leaving a clean precise shoulder for the brake or can to index up to dead flat and tight.

Have to hear from Dinny if that was his situation prompting this thread - tool clearance - seems like it was. The half center might be all it takes too.

I'm pretty cool with through the headstock, threading toward the shoulder, living on the edge! And cutting the crown then too as I have been learning. Recently got some advise on making an internally threaded gauge to fit to also. Pretty fun machine. Definitely interesting the many many things to learn.

Well I always cut my shoulder clearance area just slightly deeper than My thread depth will be . I use Back gear so slowly cutting , and a 2-3 threads width clearance and a quick hand stopping the carriage and you wont crash a bit or have to cut threads in an Unconventional way. This doesnt hurt a thing and the attachment screws up tight. I would rather have my cutter heading away from the muzzle and live center and makes it easier to use the compound rest . Its much easier to dress up the seat face of the barrel to 90 Deg. after threading . Old School Baby !

Here is what I use for threading Barrels and shafts, bolts , etc.





I grind my own tooling for Acme Threads etc. since you may not find them for sale...
Rich

Here is another trick , undercut the minor diameter at the muzzle by .010 for clearance and then start the threads to the shoulder length needed.


This is an exaggerated example to show as it can be done at the muzzle as well.
Rich

The half dead center even allows some face work. I like the Warner tool high speed.insert tooling for most barrel threading. I recently got a carbide one for 55⁰ whitworth threads and running the spindle at 180 rpm it yielded good finish. It is full profile 12 TPI cutter.

Make your crown saver long enough that the tool will have clearance from the center. About a 1/2" proud of the muzzle should be plenty. I prefer to make them from brass. A piece of 3/8" or 1/2" round brass stock should do it. Then lathe cut your threads. The whole job would probably take about 30 minutes.

I would never use a dead center in any bore that mattered. Buy a live center that you can turn down to about 1/2" diameter or just get one that already is and you're set. There are plenty of single point carbide indexable holders on the market that work very well. I have one that holds the tool vertically and have machined some of it away. The tip extends enough that on a rifle barrel, unless it's a heavy contour, it can be turned upside down and ran away from the shoulder.
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In re-reading this, it seems like his main issue was how to center the breech end of the barrel. First choice would, of course, be to remove the barrel from the receiver. Choice number two would be to use a mandrel in the action. Alignment would not be perfect (without considerable luck) but should be OK. GD

I've threaded a number of barrels on rifles that have already been fired and have a known accuracy. The dead center has had zero effect on accuracy. A prominent Arizona gunsmith turned me onto this method. I haven't found a simpler way of doing it.

As far as the beach end. I've threaded/ crowned a few that couldn't be removed from the action by grabbing the action with a 4-jaw and indicating the outside of the barrel at the front of the action.

Wow. This grew into something way different than I ever imagined it would become. I was taught to indicate the muzzle true and round by inserting a gauge pin in the bore rather than indicating off the barrel OD. All I wondered was how to get the barrel indicated true round when the live center (and an aluminum extension) are stuck in the barrel and I turned it on the live center.

Why use a dead center at all? With an extended live center that's turned down you have the perfect tool. The dead center having zero effect on accuracy depends on the person doing to job too. If he doesn't use enough grease on it or overheats the area and the grease runs off there is a potential for galling. I see no need to chance any of that.

We've pretty well beat the subject to death, but I thought I'd share the anecdote of a rifle just brought to me last week...a new Weatherby Camilla, 7mm08. Guy bought it for his daughter, it shot well with factory ammo, but she complained about recoil and started flinching. Without further thought (like loading down) he hauls it off to a gunsmith in the city for a muzzle brake. 250 bucks later it comes back, will not group, 3+ inch groups. So he hauls it to the village blacksmith...me. I am curious as to what went wrong so I started measuring stuff. The bore is not concentric with the bbl OD. Not horrible but around .0015. Lot's of bbls like that, no big deal, right? Measuring the screw on 1/2-28 brake (no brand name on it), the [bleep] thing is non concentric bad, like .004 out.
And now I suspect the 'gunsmith' cut the male thread on the bbl concentric with the bbl OD instead of the bore center. And then the 'gunsmith' cut the male threads pretty deep in the barrel...I'm estimating a hardware store fit of 60%...lots of wobble clearance. I don't know what's right, but if I was doing it I'd like to feel some interference as the brake was screwed on.
I guess this is a long way of saying little things matter, a thou here, a thou there...they don't add up, they multiply exponentially. So IMO there is nothing wrong with hashing it out in detail on a forum like this...to get better jobs in the end.
What am I going to do for my customer? Make a thread protector, develop a 120 gr light load that is accurate, and tell him to forget the brake.

Another simple work around is to turn a bushing to press onto the barrel and use that for steady rest contact.

If you want a low clearance threading tool, use a parting tool and gring to profile.....just dont get greedy on the cuts as it lacks side to side rigidity.

You can turn a "pipe" with two sets of set screws to allow jacking into square/concentric. Grab that with your 4 jaw and a steady....rock on.


Lots of ways to burn the hair off this cat.

They do add up. That's why learning to work to the utmost in perfection is just a good work habit to develop.

This is similar to the route I plan to take. First, I'll make new brass bearing surfaces for my steady rest. That is, if I can't find roller bearings that will fit it.

This is where I got mine.
https://www.mcmaster.com/products/bearings/

Been away working up north. Thought I'd asked at the time, apparently didn't. Pure curiosity.

When one is set up like shown in this picture and the threads are complete, what about the crown? Have you cut the crown previously, doing it afterwards or what? Of course I am not talking about a thread only job. Say you were to cut to length, crown and thread. Say a recessed target crown or even an 11°.

Understanding there's many ways and often things can be plenty good enough to get'r done for the intended purpose.