Lathe spindle dividing - resolution calculations and help!

[craynerd]

1-250 divisions for clock wheels.

[komatias]

A timing belt will allow you to disengage the stepper easily so you can use the lathe as normal. Nothing stopping you doing a 4:1 reduction and then doing 10 or even 16 or 32 microsteps. As the rotational speeds will be low, 32microsteps will be fine if you selected driver allows them.

In theory your resolution would be: 360/(200*4*16)=0.026deg which equates to 1minute 33.6sec of a degree or half that with 32 microstepps

If you are concerned about back driving then you will need a worm gear.