Field fatigue failures occurred in a hand-operated gear shift lever mechanism made of 1049 medium carbon steel hardened to 269 to 285 HB. The failures occurred in the 3.18 mm (0.127 in.) radius. Redesign increased the shift lever's diameter to 25 mm (1 in.) and the radius to 4.75 mm (0.187 in.). Also, instead of the as-forged surface, it was expedient to machine the radius. The as-forged surface at 360 MPa (52 ksi) maximum working stress would not ensure satisfactory life because the recalculated maximum stress was 390 MPa (57 ksi). However, the machined surface with a maximum working...