Hydraulic fitting assistance needed

[skeer]

SAE/orb threads are straight threads and not compatible with tapered NPT threads


It’s been a standard naming convention from US military aircraft in the 1930’s, and industrial JIC fittings post war (same dimensions except looser thread tolerances)

I am not sure how -1 = 1/16 fits the definition of arbitrary? It’s very deliberate and systematic.

It's also cryptic AF. Just another instance of 'that guys system isn't good enough for us, let's make our own'. IMHO.