torquing barrel nut

[Dave Hoback]

Yes, you are correct. Sorry. The math involved before hand.. finding the Pitch Radius using ES, TD &TD2 is extremely important. Forgive my over simplification of simply the thread height. But it’s still numbers in, settings made and threads come out. There’s no mysticism.. no art, right? The machine only knows to do what the user tells it. And of course it’s tolerance holding capability, right? My point was a slightly tighter/loser nut doesn’t add to accuracy potential. (And I’m speaking about bore/thread cutting squareness) But the actual “play”, only matters to the clamping torque, right?

I think Fuj’ had a bad specimen. It happens. I’ve had two of these & they don’t rock when threaded on. But they aren’t as tight as other nuts I’ve felt.

[charlie b]

Play in the nut should not matter that much. The squared faces of receiver and nut along with the concentricity of the threads of the barrel and receiver are the important parts. A corollary can be made to a shouldered barrel. The barrel threads and shoulder must be square to the receiver threads and face. The taper of the threads will 'center' the barrel in the receiver bore when it is torqued down.

The play in the nut will affect the strength of the threaded portion. Not really an issue for our application.

I would assume (bad thing) that most of these nuts are being made on a CNC. If so it could be as simple as someone setting up the machine wrong, or having an improper cutting bit installed. If the mfg relies on manual QC they might not check carefully enough. Easy enough to mess it up. Sometimes a nice phone call or email can fix the issue.

[Robinhood]

The taper of the threads will 'center' the barrel in the receiver bore when it is torqued down.

[charlie b]

Do you think something else will center the barrel? There is slop in all threaded connections. The receiver face and nut face will make the barrel stay in line with each other, but, neither will center the barrel.

[Dave Hoback]

I certainly defer to Robin on single point threading. I couldn’t tell you which bits work best, or give pointers. I simply understand the “HOW To” of doing it. Conceptual knowledge, I don’t have working knowledge as I don’t have a lathe.

[Robinhood]

There are forces being applied outside of the thread surfaces being pulled together. Those forces can and do pull barrels off center. When you move that thread off center the barrel now is held back on the side that closes up and that pushes the muzzle in the opposite direction. I have spent the time with test indicators and V-blocks and loose thread fits never have satisfied my tolerences. I could have done something wrong. The plan is to get everything right but sometimes a theory kicks your butt.

[Fuj']

There are forces being applied outside of the thread surfaces being pulled together. Those forces can and do pull barrels off center. When you move that thread off center the barrel now is held back on the side that closes up and that pushes the muzzle in the opposite direction. I have spent the time with test indicators and V-blocks and loose thread fits never have satisfied my tolerences. I could have done something wrong. The plan is to get everything right but sometimes a theory kicks your butt.

Yes Sir !! I've run the mill on just about every aspect, of fitting things up.
Spent more hours on the bench then I should have. I have 7 nuts in a box
that I went thru to always find the one that is the tightest fit for a particular
barrel. I also have 3 PTA actions that I pick to have the tightest barrel thread.
A sloppy action fit, combined with a sloppy nut equals target disasters. Other
then my fire forming barrels, all my PTA barrels are shouldered.

[25-204]

You do realize that the distance from the center of the barrel to the square hole in the wrench for the 1/2" square drive will multiply the torque applied. By how much I don't know. I don't use a torque wrench, just tighten them by feel.

[Dave Hoback]

You do realize that the distance from the center of the barrel to the square hole in the wrench for the 1/2" square drive will multiply the torque applied. By how much I don't know. I don't use a torque wrench, just tighten them by feel.

Not when the the barrel nut wrench is positioned 90 degrees on the Torque wrench. Torquing in this fashion yields precise values. This is known by those familiar with Savage & other Barrel Nut setups. (AR15,AR10)

[Rocketvapor]

Old thread, but comes up often.
Torque with wrench IN LINE has a multiplier.
Arithmetic, not Algebra.
I have an 750 in lb wrench that I calibrated (just me being anal) @ 600 inch pounds (50 ft lbs) with dead weight.
Distance from drive center to center of grip area is 11 inches.
My barrel nut wrench is 1.5" from center of nut to center of 1/2" drive socket.
The multiplier for this set up is total length (11" + 1.5") divided by torque wrench length (11").
When wrench clicks @ 50 ft lbs, the multiplier makes the applied torque 13.6% higher, or 57 ft lbs.
Many want to hold everything with the torque wrench 90 degrees to the barrel nut wrench which is fine.
I just find it easier to hold with the two in line.

[aldan]

I am more confused after reading this than before