When the steel is fully hardened, it is in a highly stressed condition and is too hard and brittle for applications. It is therefore necessary to relieve this stressed condition, increasing the toughness and ductility, while retaining sufficient hardness and strength. This change is made by the application of a heat process known as drawing or tempering which consists of re-heating the quenched steel sufficiently to transform the hard martensite into other softer carbides. Different degrees of hardness can be developed in the steel by utilizing different drawing temperatures. The higher the drawing temperature, the softer the steel becomes. The tempering must be done as soon as possible after the quench in order to promptly relieve the quenching stresses.

Double tempering is a wise precaution. It is a corrective treatment which Knight's recommends. Also, different degrees of hardness can be developed in the steel by utilizing different drawing temperatures.

Knights Dragon Fire Furnace features an improved heavy duty guillotine door with seals. The door lifts and lowers easily. The programmable Watlow control is simple to operate with 24 steps in four files. An alarm or signal light signals when the cycle is complete. The furnace can also use inert gas for use with air hardening steel providing a clean decarb-free heat treated part.