What ratio to use for stepper motor drive?

My home-built knee mill conversion uses toothed belts and pulleys to
connect the stepper motors to the lead screws. I used the same
diameter pulley on both motor and screw for a 1:1 ratio. My
Compumotor controllers are configured for 1,000 steps per revolution,
so I provide 5,000 steps per inch of travel for a resolution of .0002
inches.

I find that the motors lack power at higher feed rates and have begun
to think that, if I put bigger pulleys on the motors, I will be able
to travel the same distance with lower motor RPM and greater torque.
I don't need that much resolution.

Does anyone have experience that might suggest a better arrangement
of motor to lead screw?

Pictures:
http://www.bmumford.com/cncmill/index.html


Bryan Mumford
Santa Barbara, California
http://www.bmumford.com