Influence of Hob Materials on Behavior of Crater Wear of Hob in Dry Hobbing : Fundamental Experiments Using Fully Coated Fly Tools

This paper deals with investigating the influences of kinds of high-speed steel hob substrates fully coated with (AI, Ti) N on a behavior of crater wear mainly, flank wear and finished surface roughness in dry hobbing. Experiments were carried out using fly tools, which were made of normal high-speed steels (HSS) and powdered metal high-speed steels (PM-HSS). As a consequence, the following points were clarified : (1) The HSS tools retard the occurrence of crater wear in comparison with the PM-HSS tools, and among them, the corresponding to SKH 55 and M 34 tools are effective for the crater wear. (2) It was suggested that the crater wear mechanism on the coated rake face of all hob substrates is that first, the delamination and/or the seizure of the coating film by the deposited metal takes place, and after appearing the substrate, the crater wear increased by the abrasive action with the cutting chips. (3) Among the hob materials tested, the corresponding to SKH55 HSS tool is suitable in terms of the crater wear, the flank wear and the surface finished in dry hobbing.