imperial thread size help!

hello,

This is my first post here, and I need some help regarding imperial
thread sizes:

I'm in the process of converting a 7x12 lathe, now almost done, but I
need to cut two small pieces for a Thomson ball screw. The plan I've
on hand says about .938-16 unified thread, and .664-32 unified also.

What are these sizes, standard or not? And where can I find taps or
threading mills for them?

Thanks alot for your help!

F.L.