They look like steppers to me?
It appears he is using the existing lead screws, which would explain the backlash in part, otherwise with a Ball Screw set up in a thrust bearing, there should be no backlash in the pulley to ballscrew mounting?
Also if you CNC with a ballscrew, you can get rid of the compound rest, and this generally allows a larger QCTP to be fitted, than normally would be the case if the comp. rest was retained.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.