Quote Originally Posted by D-man View Post
Yep, defiantly 18 teeth on motor side and 90 teeth on large pulley to pinion
In that case it is definitely a 5:1 ratio, so with the 100 step setting, the big pulley should turn once with a move of 80mm (16x5).

Once that's confirmed, work out the tooth pitch. Measure over as many teeth as you can, then divide your measurement by the number of teeth you've measured over, then multiply by the number of teeth on the pinion (23).
Then that will give the distance one revolution of the pinion should give.

Then divide 8000 (number of steps for one revolution), by that distance, which should give you the correct steps per mm.