Quote Originally Posted by the great waldo View Post
Hi All
I'm just about to order some wire for my never ending cnc project and have thought myself into the ground over the wire sizes.
Have I got this right ?
the DC + V and -V (in my case 45v 7amp servo supply) roughly 1mm or 1.5mm wire
Yes, 1mm will be more than enough.

Quote Originally Posted by the great waldo View Post
Would I be correct in thinking that on a normal stepper driver the dir and pul outputs carry the power to the stepper coils ?
No that's not correct, Dir and Step are low current INPUT signals, they don't send anything out. This is the same for steppers or Servos.

It's the Drive OUTPUTS, usually marked A+ A- B+ B- on a stepper or U V W on a servo that are the high current wires. Wire size will depend on motor size and cable length but for a typical 3nm stepper with 3 to 5Mtr cable lengths then 0.75mm/2 to 1mm/2 works fine, don't need anything larger than that.

For smaller servo's 200w to 600w then 1mm/2 to 1.5mm/2 will work, again depending on cable length. For larger servo's it will be anywhere between 1.5mm/2 to 4mm/2.