Gunsmithing Barrel tenon question.

[skog]

Getting ready to start making some chips for a couple of 700 builds I have in the works. When it comes to threading the tenon how does everybody machine the relief for the thread to end? I have threaded quite a bit but all of it has terminated in a .125" wide machined groove. I dont want to loose that much thread for the tenon. In some of the pics I have seen here some have a narrow groove while others like the the thread just ends ala pipe theads style. How wide do you machine your termination groove while still providing enough relief for the cutting too to finish the thread?

Also figuring the minor diameter to know how deep to cut relief. Is this the correct forumla? min ida = maj dia - (1.732 x pitch) The math makes since but when comparing them calculated diameters to the tables in the machinist handbook they are off a bit.

thanks
skog

 

[eddieharren]

Re: Barrel tenon question.

I do not cut a deep or, wide relief groove on a Rem barrel. I'm always thinking about setting the barrel back sometime down the road. I do make a very small relief at the tenon/shoulder junction to allow the recoil lug to make full contact.

 

[bohem]

Re: Barrel tenon question.

I've done it a couple of ways, but the latest one I did I used a grooving tool that was designed for snap ring grooves on shafts. It cuts an 0.050 groove with a 0.010 radius in the bottom corners for stress relief. I only cut the groove deep enough to clear the tool tip at the thread root plus 0.005"

The guys that don't need a relief groove are either much more talented manual machinists than I am or they're using an NC lathe. I'd like to be able to do it one way or the other, but for now, I just use the relief groove.

 

[AKA-Spook]

Re: Barrel tenon question.

Mark the thickness of your recoil lug on the tenon and withdraw the tool once you're just past the mark, leaving an untouched diameter for you recoil lug to fit to.
Works nicely if you ever want to rechamber.

 

[300sniper]

Re: Barrel tenon question.

for a 700, i don't use a thread relief nor do i plunge my tool in at the shoulder to remove the tool radius. i machine a chamfer in the recoil lug instead. i also prefer .300" lugs because of the extra "breathing room" when threading and setting the shoulder back to time the receiver.

 

[skog]

Re: Barrel tenon question.

300, do you have a pic that show how you terminate a thread. I Cant seem to find one in either of you build threads. I like the recoil lug chamfer idea on the muzzle end. I think I am going to try that on one and see if I like it. Got to open the hold anyway for the new major dia.

skog

 

[300sniper]

Re: Barrel tenon question.

i don't think i have a picture showing specifically how i end the threads. i just back out my cross feed and disengage the half nut at the predetermined spot. i am doing one tomorrow and if i think about it, i'll try to get a picture of it.

 

[300sniper]

Re: Barrel tenon question.

here is one i just came across in my photobucket account.