How to indicate chamber end of a barrel when cutting threads?

[Lima9]

I have a question. A friend would like me to crown and thread a rifle barrel for him. The headstock on my Polish Famot / Toolmex lathe (14x40) is too long. I'm going to have to set the chamber end in a 4 jaw chuck and use a steady rest. It's obvious how I would go about indicating the muzzle end. But how would I indicate the chamber end while its in the chuck? Am I missing something here? Sorry for the "new guy" question? Thanks for your expertise and advice....

 

[Artv]

I have a question. A friend would like me to crown and thread a rifle barrel for him. The headstock on my Polish Famot / Toolmex lathe (14x40) is too long. I'm going to have to set the chamber end in a 4 jaw chuck and use a steady rest. It's obvious how I would go about indicating the muzzle end. But how would I indicate the chamber end while its in the chuck? Am I missing something here? Sorry for the "new guy" question? Thanks for your expertise and advice....

Is it at all possible to put a center in the spindle and turn it between centers? If you chuck in the 4J, be careful that you tighten enough so that you don't push the work back into the spindle, hence I usually turn between centers.

If using the four jaw and steady, use an indicator rod and indicate the point on the rod close to the muzzle and another point at the tip of the rod. If you only have one indicator, set it on the saddle and run it back and forth.

Art

 

[Lima9]

Thanks Art. I'm assuming that if I indicate on the bore pilot close to the muzzle and on the bore pilot as far away as possible I should be good. How long of a muzzle pilot would you recommend? Thanks

 

[Artv]

Thanks Art. I'm assuming that if I indicate on the bore pilot close to the muzzle and on the bore pilot as far away as possible I should be good. How long of a muzzle pilot would you recommend? Thanks

It depends on the caliber as to what is available. Usually .17 or .22 have separate rods. Then there are rods with replaceable pilots that cover a range and are tapered to snug up in the bore. Some have two pilots and don't taper. Usually six to nine inches sticks out for indicating. This is more than enough to give you the accuracy you need for threading.

Art

 

[MilGunsmith]

Are you threading for a brake or a suppresor? If the bullet clearance thru the suppresor or brake is tight, to avoid baffle strikes, you will need to insure that the bore is indicated in as if you are doing a chamber. Use a range rod and indicate on the rod in two locations at once.