I built my machine using a part finished Rockliff D with moving gantry I then redesigned and stiffened the frame as needed. The nominal bed size is 1200mm x 600mm and I have been using 8mm stainless steel threaded rods to drive each axis. This has worked out well, accurate but slow as the amount of whip in the 1200mm screws is unacceptable. I have bought some 10mm dia. 2mm lead single start trapezoidal screws that I hope will cure some of the problem. I am going to make the anti backlash nuts from Polymorph moulded round a section of screw placed in a 15mm deep box mould. has anyone used this material. Finally I am trying to confirm my calculation regarding linear movement of the new screws. 2mm lead =TPI 12.7 threads in 25.4mm [1inch] and that should give me 0.0787mm for single turn. If anyone knows any different please let me know