I have a book or two, in storage.
I bought them because I was working on small ball valves for refrigeration.
All the other features of the valves had been messed up along the way, but the seats worked reliably.
They comprised a machined TFE ring, with squarish 'corners', formed as chamfers in a screw machine (and possibly tumbled to remove burrs, I don't remember), that was crushed into shape as the valve was screwed together axially. I.e., the seat surface was produced by the ball itself, inducing a LOT of plastic deformation in the originally square sectioned blank. No equations found useful.
Larger valves typically have complicated chamfers where the seat will eventually be; I'm not convinced it does much good.
Mike Halloran
Corinth, NY, USA