[JohnG1931]

I think the most costly parts for a DIY are the ballscrews and nuts. I have built my own, since I wanted to automate 10 machines. I built my ballscrews from 4140 steel. It's better to have them heat treated. heat them until they are non magnetic and then quench in old motor oil. Best to build an electric frurnace for the heat treat, but not essential especially for only one or two. Castable refractory rated at 3000 deg F is OK 5000 deg F lasts for ever, with KANTHAL or Nichrome wire.
If you use a furnace you will need a good pyrometer, I use a liitle 1"x11/4" x 4" digital temperature control calibrated for deg K and chromel alumel thermo-couple, and an ordinary digital volt ohm meter calibrated for deg K and chromel alumel as backup. My actual control element is a Solid State Relay because the digital controller may not be able to carry the current load needed for the furnace. If possible choose a PID algorithm in the digital control

The only tricky parts are the ballscrew nuts. These are three concentric sleeves. The inner one has a groove 1/2 the ball dia. The middle one has a slot of the ball diameter, and the outside one has either a tube wth ID = the ball dia, to return the balls as they circulate, or an external groove for return and an outer sleeve to hold everything in place. I make my grooves spiral to allow a little space between the balls,
but I think you could make them straight, or even two at opposite ends of a diameter of the nut. You do need to be careful with the lengths of the slots to avoid backlash. If you can heat treat the sleeves, so much tne better, but you then might need to clean them up with a lap or an oilstone.

As I think about it, a better design might be to have 4 slots, each one straight with a single adjustment for all on a fine screw thread to set the lengths exactly right.
Sincerely JohnG1931