No-matter how you go about it - IF you can make this thread to print - you will constantly be chasing offsets and R values to keep it in tol.
Had a very similar part a number of yrs ago in 410. Not allowed to roll them there either. I tried everything. Even single pointing "roughing" it - and then running a round adjustable die over it for clean-up, but nodda.
I had one flavour of round adjustable die (Poland) that did a swell job. (I had tried many diff flavours.) Untill the supply ran dry. Next batch that came in would not produce possative results.
Tried a die-head as well.
My thread was only 5/16, and I don't recall the length. It may have been a little longer/D than yours. ??? If it would have been a fine thread - life would likely have been much better. ???
I ended up giving up. That is the one - or possibly 1 of 2 parts (not sure what the other one would be???) that I could not produce.
(Even tho I did ship quite a few early on, but then couldn't replicate in a timely fashion.
Only thing that I don't think that I tried was altering the material via HT. I don't remember if that was allowed or not. ???
Now if the whole part is only 3/8" round then a no-brainer would be to stuff it in a Swiss, but if the body of the part is bigger'n 3/8 - then that trick won't help either...
I never understood the reasoning for the no-roll rule. Can some-one shine some light there?
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Think Snow Eh!
Ox