Hey John,
Hood is right, he's bad about that. You will want at least 100 IPM. If you are running a screw that is 5 TPI, it has a .200" lead. It will have to turn 5 rounds to travel 1 inch. With 2-1 pullies that makes it 10 revs of the motor to move 1 inch. I think a 2000 line encoder (let someone confirm this) will take 8000 pulses to turn 1 round. Your max speed with this set up would be 45,000/80,000=.5625 rounds per second X 60 = 33.75 Inches per minute. It will run like this but unless you are very patient, you will not be happy.
Brett