Gunsmithing Lathe Topic. Live center on crown?

[microsuck]

So I was taught that when center drilling its important to have a perfect 60 deg shoulder for the live center to rest in. The other day I saw another smith just stick a live center in the muzzle and turn away. I cant help but think that would be bad for the live center or crown. Is that generally accepted practice? Over time I imagine it would cut a ring around the live center, ruining it.

At the bare minimum would would need to recut the crown again after you were done.

 

[Raven 6]

Re: Lathe Topic. Live center on crown?

I've seen guys do the same thing all the time, and it usually does cut a ring in the center. Not good if you are tring to get everything you can out of a barrel as far as accuracy goes. If you want it done right you you should put the 60 degree chamfer in the muzzle first, then the center.

 

[wnroscoe]

Re: Lathe Topic. Live center on crown?

I can’t see how using a live center would be conducive to extreme rifle accuracy and results that were dead nuts. If the barrel was/is too short to work in the head stock a fixture should be made so the barrels breech could be screwed into it and held in the spider. That way, the muzzle could be worked in the chuck/head stock.

If a person’s hell bent though to run the muzzle in a live center then yes, a 60 degree chamfer should be cut.

 

[JJones75]

Re: Lathe Topic. Live center on crown?

I'm sure that these can be a life saver , but like wnroscoe said , your not going to get dead nuts accurate with a live center no matter how well your tailstock is setup and how good the center it will be some runout , this if you put one of these in the mix with it minimum .0002" concertric , you will have tolerance stacking.

Foir the guy builing a deer rifle that not worried about squeezing the last little bit of accuray out of his rig I'm sure these would work fine

http://www.brownells.com/.aspx/pid=22326/Product/CROWN_SAVER_trade__LATHE_CENTER_COVER

 

[microsuck]

Re: Lathe Topic. Live center on crown?

That makes sense about the jig. I would guess it is just a long tube with the correct receiver threads on the inside of one end. Does anyone have a picture? This has peaked my interests. My spider to chuck distance is 23.5 inches, so I am kind of screwed for 24" and under barrels.

 

[wnroscoe]

Re: Lathe Topic. Live center on crown?

I made two of these, one 5" long and threaded 1.0625"x16tpi and one 12" threaded 1.0625x16tpi on one end and 18tpi on the other end.

Here's the short one.

Do your breech work first then muzzle work. For barrels that have already been cut down and in need of breech work make a tapered sleeve with recessed set screws for the muzzle end and let that ride in the spider. You can also make a larger fixture simular to a receiver truing fixture for barrels to go in and do the same thing. Youd have to have a small fixture to screw onto the threads though so they would get damaged in the spindal bore when working the muzzle end.

 

[GasLight]

Re: Lathe Topic. Live center on crown?

Did you make those extensions out of solid stock, or out of tubing? I just picked up some Schedule 80 2" ID pipe to make my truing jig out of, but need to make some extensions. I really need to make a 'short jaw' chuck like 300Sniper's.

DD

 

[300sniper]

Re: Lathe Topic. Live center on crown?

i am pretty sure i used 1.25" od, .125" wall dom tube to make my extension. using that size tube is less work than solid because the id was close enough as is. that and the fact that i have a bunch of drops of that tube laying around.

 

[GasLight]

Re: Lathe Topic. Live center on crown?

That is what I'll have to look for. I looked through the remnent pile today, but should have known what I needed and just had them cut it...

Oh well, next trip

 

[wnroscoe]

Re: Lathe Topic. Live center on crown?

I used bar stock because that’s what I had. If I had my choice I'd use tubing with an appropriate ID

 

[Mgordon]

Re: Lathe Topic. Live center on crown?

I made the exact same thing, but mine is about 14" long, One side is threaded for Remington barrels and the other has an external thread and a very small barrel nut for AR-15 barrels

 

[zenbiker]

Re: Lathe Topic. Live center on crown?

Those extensions are a great idea, wish I'd come up with it about 2 years ago. Now I can get almost everything through the head; thanks, guys. Oh, I assume you trued the O.D. between centers before cutting the threads...