I'm in the beginning stages of designing a CNC router and just need a sanity check.

I'm thinking of using a belt drive for the Z axis with no reducer. If I use a pulley with a 1" diameter, a 0.9 degree step is... uh.... (brain hurts)... 0.00785 inches.

I plan on doing 2D cutting almost exclusively on my machine. Z axis resolution is not a priority for me. This is plenty of resolution for my Z axis, and if I want more I can always microstep, right?

Let's say my router and the Z carriage weigh a total of 10 pounds. Now, if I want to move the Z axis at a rate of, say, 1 inch per second, I need a motor that will do 128 steps/sec with a torque of 5 pound-inches (10 pound load with a 0.5" radius), or 80 oz-in. Uh... right?

It seems that many NEMA 17 sized motors would be able to direct-drive a Z axis in this manner.

Is there any reason not to use such a simple setup? Am I missing something terribly obvious?