AISI 1045 steel has a carbon content ranging from 0.42% to 0.50%, the use of AISI 1045 steel as engine spare parts components such as gears, shafts, crankshafts, chains and piston connectors. Efforts to make steel more resistant to stress or pressure is by cooling. The purpose of this study was to determine the effect of variations in cooling media on the hardness of AISI 1045 steel, the type o…