How Do You Harden & Temper Mild Steel?
Hardening steel is an essential part of any blade-making process. When exposed to heat, carbon molecules in steel realign themselves in a harder, stronger pattern, allowing a blade to hold an edge. Two processes are necessary to harden steel: the initial hardening, or heat treating, and tempering. Poor motor oil into a shallow pan and light charcoal or a torch. Use pliers to insert your steel blank into the center of the coals or torch flame. Allow the steel to become a deep cherry red and remove it from the heat. Do not let the steel become bright red or orange. Quench the steel in the oil. Dip the blank vertically, since rapid cooling on one side can cause the steel to warp. Slide the steel into the oil until the blank is covered, and hold for 5 seconds. Remove the steel and set aside to cool completely. The steel is now heat-treated. Clean off the oil when the steel is cool to the touch, and use steel wool to remove corrosion on the surface. The steel should be bright and reflective
