Grind hardening is an alternative process to the conventional quenching process. The heat generated during grinding transforms the surface layer of workpieces into the martensitic structure. In this study, we simulated the temperature distribution during grind hardening to investigate the effects of heat on the changes in hardness and microstructure with different regrinding values using AISI 5140 alloy metal. We also compared the experimental results of single- and double-pass grind hardening processes. The results showed that the regrinding value affected the lateral distribution of hardness on the surface of the metal during grind hardening. The process created a softening width between the first and second ground layers, where a decreased softening width indicated the improved efficiency of grind hardening. It was found that double-pass grind hardening yielded the desired grinding results that reduced the softening width. The results of this study obtained using the AISI 5140 alloy metal also suggest that double-pass grind hardening can be used in high-efficiency quenching for various alloy metals.