高強度球状黒鉛鋳鉄の歯切り加工に関する基麓研究 : 第2報、ホブの最適逃げ角の研究

This paper discusses the hobbing of gears made of austempered spheroidal graphite cast iron, which has become an object of attention recently as a new material for gears. This iron has many advantages, such as the properties of a cast material and a high strength equivalent to that of steel, and is also an economical material. However, this cast iron is hobbed before heat treatment at present, for the hobbing of teeth of a hardened gear blank is considered very difficult. Yet, if the cutting of a hardened gear blank is possible, the cost will be lower because the gear can be used without performing a finishing operation on the tooth surface removing the distortion from heat treatment. In this paper, a basic test is conducted by using a TiN-coated fly-tool having the same form as one blade of a hob. Next, a hobbing test is conducted using a TiN-coated hob with a large clearance angle of 15°. As a result, the following conclusions are obtained: (1) A groove length of only 3.75 m can be achieved for the work by a (TiN-coated) fly-tool with a clearance angle of 12°. (2) A (TiN-coated) hob with a clearance angle of 15° can apply to ADI. (3) The accuracy of the tooth profile and the tooth trace of a hobbed ADI gear correspond to the JIS 1st and 4th grades, respectively.