We typically use a 1/4 microstepping for lead screws, but you want to determine the microstepping only after you determine what resolution you want on that axis of the machine.
The formula:
Resolution is steps per inch or steps per milimeter
I will go over this using steps/inch:
steps = motor steps x driver microstepping
inch = the amount of travel with one full stepper motor rotation
In the case of our 1/2" 5 start 10 TPI lead screw, the axis will travel .5 inches with one stepper motor rotation.
Let's use 1/4 microstepping (4 microsteps for each stepper motor step)
Therefore:
(200 steps x 4) / .5 inches =
800 steps / .5 inches =
1600 steps/inch
Now let's use 1/2 microstepping (2 mistrosteps)
(200 steps x 2) / .5 inches =
400 steps / .5 inches =
800 steps/inch
Remember that increasing microsteps, the torque is also reduced, but the smoothness from the motor is increased.
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With a 1/2 lead screw what is the optimal steps for the stepper motor driver 1/16, 1/8, 1/4 etc