I've got a question about stepper motor power. The CNC machine I'm working on is going to need some real lifting power for the "Z" axis. On the following web page can you tell me how to determine what oz. in. torque I will need to lift approximately 35 pounds? Should I slave two motors together to get better torque?

http://www.kelinginc.net/SMotorstock.html

I'll be using a 1/2" x 10 tpi ACME threaded rod for the prototype and then will convert later on to ball threads.

Thanks,
Greg