I'm using Oldham Couplings on the X axis but they're the grub screw variety. The motors are 3Nm. My main concern is the Z axis...I've just weighed the head and the AC motor and it comes in at a whopping 37Kg. It will probably be closer to 42Kg by the time I fit the drive, handles and other gubbins. There's no counter weight or gas strut, so will these motors be man enough at 3:1 ratio? Is the 1605 ballscrew a bit small, particularly the 10mm pulley shaft?

I'll probably get the Y and Z shafts/pulleys keywayed but I'm now a bit concerned that I've undersized the Z axis. What do you more experienced fellas think?