Basic Study on Cutting Forces in Gear Cutting : Theory of Cutting with Two Continuous Symmetrical Cutting Edges

Abstract

In hobbing, the hob cutter has many cutting teeth, and moreover each hob tooth has three cutting edges. When a hob cuts a gear, each of the cutting edges of one tooth produces one chip simultaneously. Then the chips resulting from those cutting edges interfere with further cutting, and the specific cutting forces become larger than those in orthogonal cutting. In this paper, the interference of chips is theoretically investigated. A basic and simple model of chip interference is the cutting of full-depth or non-full-depth triangular cuts. Thus, the specific cutting forces in non-full-depth triangular cuts made with a point nose straight tool are theoretically investigated in terms of various included angles. The result shows that the specific cutting forces become large when the included angle of the tool is small. The specific cutting forces with an included angle of 90 degrees are about 1.3∼1.35 times those produced by a flat tool.