Quenched and tempered 42CrMo steel is a commonly used material for critical components such as high-strength bolts, spindles, and transmission shafts, where fatigue failure induced by alternating loads is its primary failure mode. Machining, as a pivotal step connecting upstream and downstream processes in the manufacturing chain, significantly influences the fatigue performance of metal parts through the surface integrity it generates. Under wet cutting conditions, this study systematically conducted experiments to investigate the effect of cutting parameters—cutting speed (v), feed rate (f), and depth of cut ( \({\text{a}}_{\text{p}}\) )—on fatigue performance, The influence of cutting parameters on surface roughness and residual stress was analyzed. Based on this analysis, a weighted standardization method integrating both roughness and residual stress was proposed for the comprehensive evaluation of fatigue life. The feasibility of this method was subsequently verified and analyzed through experiments. The results indicate that cutting speed exerts the most significant influence on surface roughness, while the distribution of residual stress is also considerably affected by cutting speed. Rotating bending fatigue tests and fracture analysis demonstrate that crack initiation and propagation result from the synergistic effect of surface roughness and residual stress, with surface residual compressive stress and its gradient distribution playing a dominant role in determining fatigue life. The novel weighted criterion proposed in this study exhibits strong consistency with fatigue life, providing both experimental evidence and a theoretical tool for optimizing cutting parameters and enhancing the service performance of 42CrMo critical components.
