Abstract AISI 1340 is a carbon-manganese oil hardening steel with greater hardenability than the 1000 and 1100 steels of comparable carbon content, and with poorer machinability than the sulfurized 1100 steels. It is recommended for general engineering and machinery parts such as shafts, gears, axles, fasteners, rollers, etc. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, machining, and joining. Filing Code: CS-30. Producer or source: Carbon and alloy steel mills.