Quote Originally Posted by m_c View Post
Opposite way!
You want to decrease speed of the ballscrew in relation to the stepper, so you get more torque at the screw. Somewhere around a 2:1 ratio would be a good starting point.

Try running some figures through the spreadsheet to see what kind of speeds you can get with different ratios, while still having usable torque to handle the cutting forces.
OK, that's certainly how I would have dealt with torque issues with a conventional motor, but I thought the whole point was that torque went down as speed increases. I see that gearing down, by say 1:2 would give twice the torque, but getting the speed up to 1800 mm/min (900rpm for the motor) for rapids will mean that the motor is well outside it's optimum torque region. Or is it the case that in practice this wouldn't be an issue?