https://www.youtube.com/watch?v=mCz9Vaw3NL8I've got a small manual lathe that I bought second hand. My father taught me the technique of taking up backlash. When you need to move the top slide out, to increase the diameter of the cut, move it too far, then screw it in to the required setting. This ensures that every setting is set pushing the top slide in. This technique works, but is annoying. On a worn old lathe it is essential.
But how does modern CNC machinery work? It seems to zip back and forth by turning the lead screw, with out regard to backlash. I think there was a short era of using two nuts, held apart by a strong spring that both takes out the backlash and creates lots of friction. Then came recirculating ball screws. The rolling of the ball bearings solves the problem of friction. Accurate manufacturing of the ball race helps, and finally backlash is eliminated by having the nut done up tight.
Then I saw this video, which looks like it is the next stage, with all the baby thread rollers rotating around the lead screw. They claim repeatability of 0.006mm. I guess this is the possible error between screwing in and screwing out to your setting. I'm not involved in this technology, I just like to watch and keep up to keep in touch with how things work.
