It is required to design a fly press, as shown in the figure, that is capable of punching 50 mm diameter circles from a 1.5 mm thick mild steel sheet. The ultimate shear strength of the sheet metal is 375 N/mm2 and it can be assumed that shearing will be complete when the punch penetrates through half the thickness of the sheet. The screw, with square threads, is made of bronze. The factor of safety is 3. The total working stroke consists of a one quarter revolution, 45o in front of the press and 45o behind the press. During the return stroke, the punch is raised by 5 mm to provide clearance to insert the sheet. The forward or working stroke is completed in 1 sec. The balls are made of cast iron, with a mass density of 7280 kg/m3 and the radius Rm is 500 mm. Neglecting collar frictions, calculate:
(i) The dimensions of the screw,
(ii) The length of the nut and
(iii) The size of the balls.
