Originally Posted by
awerby
Horsepower is a function of torque and speed. A motor can go slowly but with lots of torque; that's what you want for milling steel. Other motors, like the RC motors you mention, go very fast but have little torque. These are less useful for milling, unless you're using very small tools, which need to go faster. With a pulley cluster you should be able to get the treadmill motor to go even slower, which would give you the torque you need to mill steel with a fairly large tool, assuming your home-made frame is rigid enough for the task. Hardened steels, or alloy steels, need to be treated as special cases - you might need carbide or even diamond tooling to deal with them.