Source and specs for Thompson Ball Bushings, Ball Screws, and shafts for rails.

I would like to build a X and Y axis using Thompson ball bushings
riding on shafts, axis driven by ball screws, and stepping motor.
When I was doing design 40 years ago, I remember that Torrington
roller bearings had to be press fit in steel, with a minimum wall
thickness in order for the needel bearings to work. Do Thompson ball
bushings have requirements such as steel vs aluminum, tight tolerance
press fit or any fit will do, minimum wall thickness in aluminum or
steel?

What is a web source for Thompson ball bushings other than eBay,
where they have reasonable prices, sell retail in small lots, and
provide specifications.

Also do the shafts that are used as the rails, have to be toleranced
to 0.0001 inch, and must they be hardened? What is a source for the
hardened and ground rods? Are there suppliers that will finish cut
them to length?

What is a retail, small quantity, source for ball screws and ball
nuts, transport grade and hardened and ground grade, with zero back
lash ball nuts? What are the different grades for ball screws? Is
there a discussion somewhere about ball screw grades, implementation
in a design (two vs one, thrust bearings, ...)?

Thank you in advance for your help.

Whelen