5steel; 2.632 in. O/a dia; 0.688 in. O/a h; 0.395 in. Tapered to 0.511 in. Id; keyway in bore full lg of bore; 0.094 in. W by 0.125 in. Deep; two thd holes one side of rotor; no. 10-24 unc-2b rh thd; holes spaced 180.0 degrees apart; 1.188 in. C to c