Estimate the torque required to “raise” the load.

1. A 20-mm power screw for a hand-cranked arbor press is to have a single-start square thread with a pitch of 4 mm. The screw is to be subjected to an axial load of 5 kN. The coefficient of friction for both threads and collar is estimated to be about 0.09. The mean friction diameter for the collar is to be 30 mm.

a. Find the nominal thread width, thread height, mean thread diameter, and the lead.

b. Estimate the torque required to “raise” the load.

c. Estimate the torque required to “lower” the load.

d. Estimate the efficiency of this power screw system.