"Threading" Eh?
Field First Sergeant "Willie" Williams, 101'st into a bridge too far, then Bastogne:
"If necessity is the Mother of invention, then ASSUMPTION is the Mother of all f**kups."
But let's open the mind to learning and research of "possibilities", shall we?
The cut is "generally" made into a cylindrical object. Surface is curved, in other words. Tooling is not often dead-flat to a dead-level radial line, has some rake angle or another, rather.
What is the angle it actually GENERATES in the stock when in use, straight-in plunge, no compound rest monkeying about, and set where the maker expected it to be?
Not ALL threads are 60-degree, not even CLOSE-to, BTW. There are "standards" for over a hundred of them, after all.
And what d'you know about "class" of thread fits, and why each has a useful place at the table that is intentional, not just the accidental byproduct of lousy QA?
The use that you - or I - are "not aware of" may be some other whole industry's ordinary Day Job rice-bowl?
Threading ain't the only determinant of an effective angle for a given cutting-tool and the material it is made of.
Sometimes it has to do with how Alloys react to tool approach angles for best rate of removal, best longevity per-edge, ordinary straight turning.
Read as: "more money in the bank, less wasted in the recycle bins of stock, Carbides, power bill, machine-wear, and hours of labour, summed."
D'you suppsoe the angle presented with only ONE of the edges active at a go might depend as much on how the insert's POCKET is aligned as on the insert shape alone?
The OTHER edges generally wait their turn, yah?
The
insert-makers might have that sort of klew? Not all that often they ship the buggers in packs of only the
one ever made, yah?
Saved the best for last. Of course.
See "boring bars". DCMT or DCGX insert. Lowly Shars catalogue.. or
"Right here, on PM", even:
Best Boring Bar and Insert Style for 6061T6
Common as dirt "shiny wood". Go figure.