Calculating the right timing pulley

[cnc2k]

how can i calculat the right pulley for my setup?

Detail of machine.
X=30", Y=53"
Gecko 320
Amatak 40v servo motor with US digital E2 encoder, shaft size 5/8"
Ballscrew ~55", pitch 15mm.

Use for cutting wood and aluminum, i want to gear it up for more speed.

Another question about the power supply. i'm planning to run the motor at 48v 8amps per/axis, will this burn the motor?

[Runner4404spd]

need more info before we can tell you anything. on the gearing... whats the motor rpm? take that number and multiply by the pulley ratio say 10 teeth/20teeth therefore = rpm/2