ＣＢＮ工具による焼入鋼の断続仕上切削における刃先形状の効果

Abstract

The CBN tool can be used for a fine cutting of hardened steel in turn for grinding. However, for an intermittent cutting, this tool comes often to over the life in an extremely short time owing to occurrence of cutting edge break. In this paper, so as to get long tool life and good surface finish, influences of tool geometry, collision means of tool with workpiece and frequency of collision are investigated. As a result of these consideration, a new tool of very long life was contrived. Main results are as follows: (1) In cutting of the shaft with two key ways the tool reached life because of flank wear. A recommendable negative land angle is around from 25° to 35°. (2) In cutting ofthe spline shaft having many collisions in number, the tool life is over in a very short time due to an edge failure. A break happens on flank face when the tool collides at tool face (Type I), and a flaking on tool face when at cutting edge (Type II). The latter gains an advantage over tool life and surface finish, and yet its life is short. (3) The new tool has a land on flank face, and is used for cutting of a spline shaft. Its failure manner is Type II. A flaking happens on the face successively at some time interval, and the cutting edge is selfsharpened at each time. Due to this action the tool life was much prolonged by 17 times of the case (2). (4) In the above case, when lifted the real cutting edge after flaking up to the initial edge height at a suitable time interval, the tool life increased further by 26 times.