Curious, what did you have to pay to have them threaded? I have a nice metal lathe and just ordered some "range rods" (they fit inside the barrel so you can indicate the barrel... centered to the bore instead of the outside of the barrel). The rods are expensive for what they are and they're caliber specific. I just got the 22 rimfire and 22 center fire. As far as threading on a lathe there's really nothing to it, just have to be particular on the set up. I've been thinking about doing some on the side, just have to check out the legal end.
I paid $99 per barrel. I bought the can from Silencer Central, and that's what they charged to thread them. I was concerned with shipping my guns and having them damaged, lost, or not back in time to sight them in for gun season, so I talked to a local gunsmith about it. He was concerned the barrel OD was too small. I had read several things about issues with barrel threading not matching the can, so I decided to have SC thread them. That way, if there was an issue, there wasn't a third party involved leaving me screwed, pun intended.
As far as barrel OD and remaining wall thickness, I figured there have been thousands of cans installed on Remington 700s. I way overanalyzed it, but talked to different can manufacturers and hopefully I got it right!
Don't have the can yet. It's going thru the ATF approval process.
Oh, thanks to responses about applying lube. Very familiar with Never Seize. And yes, a little can go a long way!!