[Zeke]

The lathe method of threading in can be inaccurate if you are manually starting and stopping the machine. They like to "coast" a few turns before stopping fully. Using the lathe's threading ability is slow. If I were dong this I'd chuck the stock in the lathe and use a hand held die wrench on a rest. If you can safely pull the rest away at the desired length, the wrench will freewheel while you wait to reverse. At that point, I'd spin the die and wrench back by hand.

You need a good flow of cutting fluid during the process. Go slow.

I'm not a machinist, so I'm taking a stab at this as a hobbyist.