having a lower turn-per inch on your lead screw kills the resolution of the system. If you're going to use Acme screws, look for 10 TPI 1 start or 20 TPI 2 start to get 10 turns per inch. Either way, the average 1.8 degrees per step motor will give you 2000 steps per inch, or 0.0005 inch resolution. Using a 10 TPI 5-start screws would give you 400 steps per inch, or 0.0025 inch resolution. Yes it would move faster, but it would also load the motors a lot more.