Don't exactly know the techinal info you want but I do know this---Threadmilling is the way to go. We recently bought an Okuma mill and have been doing quite abit of threadmilling on it. We've been cutting 1/4"npt female threads in 316 s.s. . I've been using an advent solid carbide threadmill with coating. At 3000 rpm I've cut over 800 holes with the same cutter! I've only had to offset my cutter a couple of thousands. Thread form is excellent!
We have a ground and hardened gage and it gages perfectly.
We recently bought an inserted threadmill--advent again ---for cutting 2"npt female threads. Again it worked beautifully. The thread form can't be beat.
Also advent has a new threadmilling software program you can get for free. Only takes a few minutes to input info and your done.
P.s. Thanks for your insight in this forum. I've learned alot.