Almost all auto gear hobs are made of high-speed steel. High speed steel is a tool steel with high hardness, high wear resistance and high heat resistance. It is characterized by excellent cutting ability and considerable toughness. Although all high-speed steels exhibit similar physical and mechanical properties, these properties can be greatly different by changing chemical composition and heat treatment. The specifications of materials shall be selected and determined under certain working conditions.
One of the more important characteristics of automobile gear hob is its cutting ability. Cutting ability depends on the combination of chemical elements of the material, including high heat resistance, wear resistance and toughness. High heat resistance – red hardness is to maintain the high hardness of materials with the increase of temperature. Red hardness is usually an increase in the amount of alloying elements. In particular, cobalt gives the material high heat resistance. Carbon and vanadium that can improve hardness and wear resistance. Generally, increasing hardness, high heat resistance or wear resistance will often reduce toughness. High speed steel automotive gear hobs usually compromise in hardness, wear resistance and toughness in order to maximize the overall performance.
The wear resistance of cemented carbide is very good, but its application in gear hobbing machine is very limited. Because the cost of carbide hob is several times that of the same high-speed steel hob, it is necessary to increase the service life of the tool and reduce the production time to make up for the increased material cost. Because cemented carbide has high-quality wear resistance, this tool is mainly used for the processing of aluminum, brass and non-metallic materials.