CUTTING FORCE COMPONENTS IN ORTHOGONAL CUTTING PARALLEL TO THE GRAIN(90-0) .1.

In this study, orthogonal cutting parallel to the grain (90-0) was made with three kinds of hardwoods, and the cutting forces were measured for rake angle (alpha) which ranged from 0 degree to 35 degrees. The cutting forces were divided into that part of the force component acting at the cutting edge and that part of the force component acting on the rake face of the knife. The true coefficient of friction (mu') in cutting was calculated from a proposed equation by means of the linear relationship between the cutting force and the depth of cut. The effects of rake angle on cutting force components and the coefficient of friction are discussed. The results obtained are summarized as follows: 1) Both parallel and normal cutting forces were observed to be greatly linearly related to the depth of cut. 2) As a whole, cutting force components decreased with increases of the rake angle except for that part of the parallel cutting force component acting at the cutting edge which had a minimum between 20 and 25 degrees. 3) The direction of the cutting force component, acting around the roundness of the knife edge, approached the cutting direction as the rake angle increased. 4) The direction of the cutting force component acting on the rake face changed linearly with an increase of the rake angle. 5) The apparent Value of the coefficient of friction (mu) increased as the depth of the cut decreased. 6) The true values of the coefficient of friction (mu') were smaller than the apparent values (mu). 7) The selection of the rake angle for the formation of a Type II chip is proposed where the normal component of the cutting force acting on the rake face is zero. In this study, it approximates 25 degrees.