In the first photo, I've taken a light pass and set a micrometer stop a few thousandths short of my desired tenon length. When I get to diameter, I'll back the stop off a few thousandths and pull the cutter out for a nice shoulder. The second photo is turned to the correct diameter.
I set the compound the same angle as the threads. Advancing the thread depth with the cross slide minimizes cutter contact and chatter, for a smooth thread cut. This is my first test fit. The brake just starts to thread. From this point I will advance the crosslide, rather then the compound, .001 per pass until the brake threads on completely. The goal is resistance free threading with minimal clearance.
I took .003 from the first test, where it started to thread, to final thread depth. Out of curiosity, I put an indicator on the brake. With the brake threaded on half way there is .002 movement at the indicator. If you did the math, you might figure there is under .001 play in the thread fit. You could shoot the rifle like this without clearance issues or the brake blowing off.