What's new
What's new

Muzzle threading setup with a long headstock?

mooseracing

Plastic
Joined
Apr 12, 2013
Location
MI
I think the heat & humidity is getting to me today. I am trying to explore using Grizzly rods for setup for threading for suppressors.

So todays trial failure had the action in the 4 jaw, with thick brass pads. Dialed in roughly the OD while using a live center. I then put on the steady rest and a home made action truing jig.

I adjusted the steady rest while using an indicator so as to not push to much one way or the other on the jig. Inserting the Grizzly rod into the barrel a few inches and then adjust the back set of screws on the jig. Move the rod to the crown, try to adjust the front and just can't dial it in. I start to get close then on spot is always out by a 5-10 thousandths.

It also seems like that is a bit of deflection in the steady rest to jig fitment. But if I run the screws down any on the steady, there is too much friction.

So what can I improve upon besides the lathe? When I through this barrel action between centers I was less than impressed by the amount of runout, so I thought this would be a good time to learn a new method. The host rifle is a Savage .223 bolt if it matters.

Thanks
 
I think with the action locked in the 4 jaw, you've got to be putting a bend in the barrel to align it in the steady with the truing jig on it. If I understand what you're doing that is.

I have a short sleeve with screws at each end I use to support a barrel in the middle when I'm turning them down. But the ends are usually on centers.

Probably better off just putting the barrel in the truing jig and dialing it in. And if the action won't fit in the spindle, pull the barrel off.
 
I concur with wesg, if you're holding the barrel in three places (chuck, front of truing fixture, back of truing fixture) you're bound to end up fighting your tooling.

I'm curious why you don't just thread using the tailstock center? You can make or purchase (Brownell's) a brass crown protector and dispense with the steady altogether.

If you can fit everything through the headstock, I just dial in a gauge pin stuck in the bore and thread.
 
If I understand your question correctly.... You might want to look into a device called a cathead. It will allow you to dial out angular runout between the bore and OD of the barrel in the steady rest.

Sent from my XT1053 using Tapatalk
 
How about a picture of your setup. That may give away what is going on. The steady on the truing jig seems a bit suspect to me.
 
Sacrificial collar just behind the thread tenon location.
Aluminum round stock, about an inch long with an OD of 1"-1-1/2" or so, whatever you might have lying around.

I always pull barrels, usually easy (except for damn Tikkas) and military barrels. Military rifle, I use snug fitting mandrels turned between centers to fit in the bolt raceway, business end in a spindle collet (collets are made to order for barrel work IMO).

Bore to match the taper of the barrel, with the large end sized so that the barrel taper will seat the collar so that the front is about an inch behind the back end of the thread tenon to be cut (allow minimal space based on clearance for tooling).

Using a 60 degree piloted center, cut a shallow (30 thou or so) center. I don't feel the "crown savers" are accurate enough to rely on for this application. So yes, you'll need to cut a new crown.

Degrease the end of the barrel. Wrap a single layer of thin masking tape or paper around the barrel where the bushing will ride (no overlap). Tap the collar gently into place over the tape/paper. Muzzle end (with the new center) in a tailstock live center, breech end of the barrel in suitable chuck or collet. Make a light truing cut across the length of the collar. OD of the collar, is now concentric to the bore at the muzzle.

Steady rest time. Set up a couple of indicators to be sure it doesn't shift when the live center is removed. Cut and thread the tenon.

Steady must be well lubed so the collar doesn't heat up, expand and lose its grip on the barrel. Just how I do it with a steady, YMMV.
 
Adjust using the back screws when measuring near the crown and the front screws when a few inches into the barrel.

Ditch the grizzly rod and pick up a long stem Interrapid indicator
 
I would remove the action and make a bushing that fills the gap between the ID of you draw tube and the barrel. Have only enough of the barrel sticking out of the chuck to do the threads and a little extra (1/2-3/4 inch). Than if you have a independent four jaw chuck indicate off of the barrels bore by using a dead center in the tail stock and a second one to go from the tail stock to the barrel bore. Put a indicator on the dead center near the barrel and adjust the chuck as needed to center you barrel. Once it is centered you can remove the center to do the machining. Keep in mind that rifle bores do not necessarily run true to the the OD of the barrel. In school we made a tool to use to center it but I can't get a picture of it till I get home sorry
 
Think a dead center set in any chuck and turned true for the head end and a plug center for the muzzle.
Yes could make the head end of brass as it would turn with the job and not wear anything.

Yes re skim head center each time it is taken out of chuck..

Simple enough set-up.. Perhaps your threading is causing too much pressure.. I suggest a fingernail sharp bit HSS or carbide is Ok.. with a 29 ½ * feed and a 5* side rake off the side cutting edge.

I take off trigger so it is not spinning round to catch something..

If you pug center both ends it is (can be)hard to get them out.
 
Think a dead center set in any chuck and turned true for the head end and a plug center for the muzzle.
Yes could make the head end of brass as it would turn with the job and not wear anything.

Yes re skim head center each time it is taken out of chuck..

Simple enough set-up.. Perhaps your threading is causing too much pressure.. I suggest a fingernail sharp bit HSS or carbide is Ok.. with a 29 ½ * feed and a 5* side rake off the side cutting edge.

I take off trigger so it is not spinning round to catch something..

If you pug center both ends it is (can be)hard to get them out.

Finally. Was wondering if there would be anyone who knew what he was doing. A 2 minute set up, no indicator required, absolutely accurate to the capability of the machine.
Of course it came from a machinist, not a hack gun butcher.
 
but I made a mistake .. to be more clear the head center would turn with chuck and the part...it would run dead true to the head stock.. and pug was meant to be plug being a very slow taper that fits onto the muzzle and rides the tail center.
This plug made between centers would be also dead true and could be used any number of time for that bore.
 
Think a dead center set in any chuck and turned true for the head end

Not sure what you are meaning by turned true for the head end? Or are you just mentioning that the center needs to be trued instead of assuming someone would?



The threading isn't causing too much pressure as I haven't gotten there yet. I'll try to get some pictures tonight of how it is setup.

I know I could fall back to between centers, but I was trying to add another way to the tool box.
 
A stub (any chunk of mild stock) can be chucked in any old or new chuck and be turned to a center point angle with a light tool bit cut so not to distort, have the correct angle and a good finish...That home made center will will run dead true to the head stock bearing for as long as it is not removed..This is a common shortcut to avoid taking off a chuck for a quick between centers job.
Yes if taken out and set in tool box it needs to be skimmed at next use. One can be made of brass for a no-mar center..Going with the chuck is gets little to no wear and will not harm an important part..

Yes the other part-end can run in a steady or to the tail stock center.

*Close work can often be done better between centers but oft times a guy will not wish to take off chuck, put on face plate and mount the head center...

Yes the drive dog is run off a jaw..best using the same numbered or marked jaw if job is removed and replaced.

Should/could take perhaps 5 minuets to make this set-up. A great way to finish a bearinged shaft to perfect with a .003 to .010. skim..(run part to the chuck's error then finish skim)

The quick chuck center turns with the chuck.. but being turned there runs dead on. A lathe fish can check the angle.. but the angle does not have to be dead perfect for a one up job... running true is the most important thing.

Centers should run very close.. a live center will run a part double the off-center error..a dead center will run very true to dead on. A live center should be checked for zero TIR. Regrinding a live center should be done in its own bearing because taking it apart you cant get it to run good enough--zero.

For a big lathe the stub center is made with a shoulder to bump the jaw(s)so high tool pressure will not move it in the chuck.

*Just thinking about the head stock end running out and then trying to hold the out end in a steady.. would make a decent lathe hand give cry...
 
Don't know if anyone but me would try this but the head stock end in a 4 jaw would/could tend to bend a barrel so getting near zero close-chuck might cause a wip down the length because of jaw angle and the like... a single wire wrap of 14 gauge copper wire and that held in a 4 jaw would/could reduce any warp. Think 14g is about .060 or so.. Yes for a one up light thread job with the out end in a steady..

Put the out end on the tail center and bring each steady jaw to feel a .002 shim. oil it up and move away the tail..

Yes try this just for fun on a piece of test stock to see if you can master it.

But yes the slow taper centered bore plug held on the tail center is still best IMHO.

With a good tight lathe reverse threading can be good because of holding the part like in a V block using two steady pads on the down side...yes going backward and away toward the tail..Mostly I am against this method.. but for a light cut threading it can be an asset. You have to sharpen the bit left hand and be 30 (29 1/2)the other way.
 
The 'problem' with a center of any kind in the headstock is that he has to pull the barrel off the action.

Or ... the center has to be a long flimsy shaft to reach through the action to catch the tail end of the chamber.

I'm still in for pulling the barrel.
 








 
Back
Top