A SAE 1040 cold rolled shaft have a yield point of 70 ksi, a diameter of 60.4 mm, and with a key of ½ x ½ x 7 in. Determine the minimum yield point in the key to transmit the torque of the shaft. (FS = 2, Ss = 0.35Sy)

4 A double-threaded power screw with square threads pushes against a load of 3,641 N at a speed of 15 mm/s. The screw has a major diameter of 20 mm and a pitch of 3 mm. The frictional coefficient of the threads is 0.25, and collar friction is negligible. What is the rotational speed of the screw in units of revolutions per minute? Type your answer 2 points

A rigid coupling with 30 inches of bolt circle diameter transmits a torque of 18,000 lb-in. The coupling material has a yield strength of 90,000 psi.  The coupling is fastened by six bolts.  Assume design factor of  N=3 Calculate the diameter of each bolt.