Cool! When I think hydraulics, I not only think fussy and precision, but BIG. Way bigger than anything I've ever made or probably will make. Then you've got the tough materials to contend with. I had an issue with very long and very tiny screw threads (over 100 tpi) that I wonder if you ever see in that chrome steel. The threads had to be perfect over about an inch. No change in PD at all. HSS, even cobalt, would wear just enough from beginning to end, that the thread was unacceptable. I could just barely do 1 thread (in 303) using Castrol Moly-Dee, that was decent, before tool wear degraded the geometry and root. Only with hand lapped carbide was I successful for many dozens of parts. Oddly, a perfectly sharp pointed tool was just as durable as one with a flat or radius, though that would never be true for a larger part.
Best,
Conrad