Hi Dave
30:1 (Based on 200 stepper) would give you 200 X 30 = 6000 steps per. 1 turn, .06 deg.'s per step, 16.666666 (steps per.) 1 Deg.
Depending on the Accuracy you need, This may be fine, Not Sure.
Mach can only move to within 1 (stepper/encoder step's), So 1 Deg move 16.666666 step's will be Rounded up to 17 steps, .00000001 to .5. Rounds Down, .50000001 Rounds Up.
Mach keeps track of the Remainders (+'es -'es), To 16 decimal places or more .00000000000000001, If my Memory is Correct.
There applied to the next move to the Nearest 1 step and so-on and so-on............
It's like your other axises, The combination of Stepper's or Encoders count pre. turn and the relationship with Gearing/Ball screw's Ratio's.
You need 10,000 steps (Per.) "Unit" (Inch or MM) to get .0001 Accuracy.
It's All a trade off, Speed and Accuracy, Best I Now.
Hope this Helps, Chip