Bending of Drill and Radial Forces in Micro Drilling

This paper describes theoretical analysis of bending deflection and anisotropic rigidity of drill, and the induced radial forces in micro drilling. The main results obtained are as follows. (1) There are two different modes of drilling which cause bending deflection of drill and induce radial forces. They are position error mode and run-out mode. (2) The radial forces induced behave quite differently between the two modes. (3) The radial forces increases as the depth of hole increases, because the rigidity of drill beam increases. (4) The position error mode induces a cyclic stress in the drill which may cause a fatigue breakage.