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  #1  
Old 05-29-2017, 10:42 PM
skeet_man

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Indicating barrel for crown in mini lathe- Best cheapest way



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So I stumbled on a JC Higgins semi parts gun last week for the princely sum of 5 bucks. Was mostly intact except for the stock and trigger guard, but was covered in a decent amount rust. I was planning on rebuilding and refinishing the gun, but after I priced out a stock and trigger guard, and figured on the time it would take, it just wasn't worth it, so I cleaned all the parts off and put them up on ebay.

That left me w/ a receiver and barrel. Barrel is rusty on the outside, but bore is immaculate (astounding on an otherwise barn-find gun). Receiver wasn't worth trying to sell, but I've been wanting to build a dedicated 22lr upper for my AR, so I'm going to see if I can reuse this barrel for that project. Cut the old chamber off and faced the breech end, will do the muzzle when I get a chance, need to decide on what I want for length.

At any rate, I'm working through the headstock on my mini-lathe. I don't have enough length to go b/w centers even if I went down to 16" on the barrel.

Since there really isn't much metal to remove I will likely chamber it by hand. However, I would like to use my lathe to recrown the barrel. Would indicating off the lands and grooves be sufficient? Since this will be a one-off project I don't want to invest in any tooling I'll never use again.
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  #2  
Old 05-29-2017, 11:05 PM
pans858
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With a dial test indicator you can probably use the tops of the lands. You might also use a pilot, which you can easily make on your lathe. That will allow you to use either a dial indicator or test indicator, and will be easier and perhaps a bit more accurate.
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Old 05-29-2017, 11:24 PM
skeet_man

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Thanks. Sry, meant test indicator, the one I have has half thou resolution.

I was doing a little research online this evening and chambering and crowning can get intimidating (and expensive) real quick depending on what level of quality you want to shoot for. I suppose I need to be realistic and realize I don't need ultra-level precision machining (and by extension equipment) for a semi 22 with a recycled barrel.

I had thought about making a pilot and indicating off of that but was unsure what the level of accuracy was, and figured a test indicator would be more accurate. Maybe I'll get a longer stem for my indicator and experiment with both methods.
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  #4  
Old 05-29-2017, 11:53 PM
pans858
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The test indicator is probably not more accurate, even if it has .0005 grads. Your dial indicator probably has a larger dial face and will easily be read to .0005 or less even though it has .001 grads. I'd suggest you make a pilot for lots of reasons. Taper it about .0005 per inch and you can anchor it in the barrel and pick up the centerline very accurately. Make sure everything is clean, and put it in with light pressure, twist slightly to install and remove. Unless you're a gorilla, you won't hurt a thing. Indicate close to the muzzle when centering in the 4 jaw chuck.
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Old 06-01-2017, 03:11 PM
donie

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I re-crowned a Ruger 22 barrel on a short bed lathe. I found the opposite end of the barrel needed support.
Some shaped soft wood wedges at the back of the spindle to keep the barrel from flopping would probably work.
I first turned a pin like described above. to help dial in the barrel.
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Old 06-01-2017, 05:22 PM
GH41

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How are you guys getting the barrel even remotely close to dialed in without a spider?
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  #7  
Old 06-02-2017, 01:12 PM
donie

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Originally Posted by GH41 View Post
How are you guys getting the barrel even remotely close to dialed in without a spider?
I find this an interesting subject. There are those that think dialing both ends of a barrel in using a spider attached to the back end of the spindle, not that important, others feel it is important.
Some lathes like the world class machine I will show here, a spider can not be used because the headstocks are too long. The Monarch here, the headstock with a jaw chuck is 28" long.

I will describe the compromise I made to align the barrel for both chamber and crown work.
The barrel end within the headstock, I machined an accurate plug the fit inside the spindle bore. I drilled the ends of the steel plug for tapered pins to fit the muzzle and the chamber end of the barrel.
The effect is, the tight fitting spindle bore plug, the centering pins accurately installed, will center the opposite end of the barrel within the lathes headstock hopefully to a reasonable degree. At any rate, I was the best I could do with the equipment on hand.
The results I experienced was all good, however I am not a gunsmith, or can say what I have done is the right way.
Any suggestions?


Last edited by donie; 06-02-2017 at 01:16 PM.
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Old 06-02-2017, 03:02 PM
GH41

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If I had your Monark I'd spring for one of these. https://www.youtube.com/watch?v=vFiLbeeZBx8
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  #9  
Old 06-02-2017, 03:19 PM
pans858
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Nice lathe, donie, double E series?

I think the OP is working with minimal tooling, and learning as he goes. In this particular case, I suggest the spider is probably not going to happen, and not that big a deal, really. Certainly it should be used any time a barrel is machined, but in this case, the job is facing, not turning. I expect the chuck jaws will do a decent enough job of keeping the angular error down, and the workpiece is fairly light. The suggestion to use wooden wedges is a good one.

Spindle speed should be kept low, maybe even 350 rpm or so, certainly not more than 600 give or take. That is insufficient sfm, but one does not want a long workpiece, not centered, to have a chance to develop any whip.

Back to the error, the crown should be perfectly perpendicular for equal gas escapement, and yes it will make the crown somewhat off of 90 degrees to the bore, but given the short part diameter, won't make as much difference as one might think. Only my opinion, others are sure to differ.

Edit: you know just about anything can be used to help constrain the off end of the barrel. Dependent on spindle bore diameter, even something as simple as o-rings or a piece of heater hose on the barrel would work just fine.

Last edited by pans858; 06-02-2017 at 03:23 PM.
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  #10  
Old 06-02-2017, 05:50 PM
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If I had your Monark I'd spring for one of these. https://www.youtube.com/watch?v=vFiLbeeZBx8
I was taken back by the fact, the machine operator simply does not know how to grind his chuck jaws true. This is very important for using 6jaw chucks.
Instead the operator made a device to tilt the error out of the chuck.

Now, in that video, a gearhead lathe with a long head stock, the operator is making no provision to stabilize the end of the barrel within the headstock.

If that is a proper way to do this type work in gunsmithing, it certainly would not be done in any other industry handling long slim work.

If one has a six jaw chuck, clamp a bar in it, and move the bar up and down, then try the same with a 4 jaw chuck. I will guarantee the 4 jaw chuck will be chosen for holding with less deflection.

Back on the lathe in the video, its headstock is too long to use a spider just like the little Monarch.

The other choice I had was to extend the barrel out into the bed, install a cathead and use the steady rest. I did not go that way because I wanted to be able to chuck the barrel up easier and go a little at a time to deal with headspace and other issues. Also, with the barrel contained in the head stock higher speed could be used for carbide.
I find it an interesting subject from the machining end.

Last edited by donie; 06-02-2017 at 06:12 PM.
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  #11  
Old 07-18-2017, 04:45 PM
55fairlane
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So I'm a little late to this party, but as a tool and die maker, I use gage pins slipped in to bore, I have a set of under (minus) and over (plus) pins....works like a charm

OR use a crown cutter from brownells....I have even made my own pilots and used a set of automobile valve seat cutters

Hope this helps

Aaron
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  #12  
Old 07-20-2017, 01:15 PM
SGW Gunsmith
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Quote:
Originally Posted by 55fairlane View Post
So I'm a little late to this party, but as a tool and die maker, I use gage pins slipped in to bore, I have a set of under (minus) and over (plus) pins....works like a charm

OR use a crown cutter from brownells....I have even made my own pilots and used a set of automobile valve seat cutters

Hope this helps

Aaron
I use the very same method, along with a four jaw, tenth indicator and patience. Works great!
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  #13  
Old 04-08-2019, 01:03 AM
6mmintl

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55fairlane has it right.
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  #14  
Old 04-11-2019, 06:57 PM
flatlander
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Both my lathes have spindles over 24" long; by the time I hang a 4-jaw chuck off the spindle nose (D1-4), the effective length has extended to a little over 27". I wind up using dummy receivers in the spider quite often to allow the muzzle of a bbl to extend out of the 4-jaw far enough to part off the required 1" (or more, depending on the desired finish length) and still be able to thread for a brake or suppressor mount, then cut the crown.

I use what PTG calls "Gordy rods" with pilot bushings to dial in the bore, whether for chambering or muzzle finishing. The bbl that's in the 4-jaw has a ring of heavy copper wire wrapped around it to allow the bbl to pivot in the jaws. This is done on the breech end of the blank for chambering & cutting the thread tenon, and afterwards, when the blank is flipped end-for-end, the muzzle is dialed in with a smaller wire ring around it.

The Gordy rod is placed into the bore, then the tailstock is run up close enough to grasp the very outboard end of the rod in the tailstock chuck. A .0001" test indicator is held in a Noga magnetic holder, and placed to indicate on the side of the rod towards the operator, about a quarter inch out of the bore. The tailstock is used to run the end of the rod with the pilot into the bore to the point under the copper ring, then the bore is centered in the 4-jaw by indicating off the rod. When that's done, the rod is retracted to the point where the pilot bushing is just fully in the bore, and the spider is used to indicate that point of the bore true. Then the rod is pushed back into the original point under the copper wire, and adjusted true again. This process is repeated until I've got at least 2" of the bore running true to the spindle bore, or more than that for a longer chamber. I want the bore where the throat is going to be located to be running true, as well as the point out at the face of the breech end of the blank. Mounting the blank in the 4-jaw with the ring of copper wire is critical - it allows the blank to pivot on the wire in the chuck jaws. Without it, the blank would simply flex in the spindle when the spider is adjusted, and you'd see very little if any movement on the indicator while adjusting the spider.

Just dialing in both ends of a blank in the 4-jaw & spider gets those two points of the blank running true. But as we all know, the bore of a barrel blank is seldom - if ever - truly straight, so having just the ends of the blank running true doesn't insure that you'll have the bore where the throat's going to wind up will be running true. Just as importantly, with the popularity of suppressors today, it's very good practice to have at least a couple of inches of the bore at the muzzle dialed-in to run as true as possible before the threads are cut for the suppressor or mount. I know of no better way to insure against a baffle strike.

Last edited by flatlander; 04-11-2019 at 07:00 PM.
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