That's a good tip about not breaking connections while live Neale - hopefully I might have had the common sense not to but I often amaze myself with my own foolishness. I suppose it's the risk of an accidental break in connection I need to be really worried about.

I will be using these digital drivers http://www.cnc4you.co.uk/Digital-DSP...?search=CWD556

I had assumed that voltage would be regulated by drivers and that they would put out the same voltage to the motor regardless of input providing it was within the input range. The specs say they can handle an input voltage of 24v to 50v. The power supply I have is only 36v - what difference did you find from running yours at 68v and does the spec say that they can take that kind of voltage?