Abstract
Carbide-tipped drills having various shapes of main cutting edges, and circular or straight cutting edges or non-cutting zone at the drill center have been manufactured and widely used in recent years. In order to compare the cutting phenomena with these drills, the tool angles such as inclination angle and normal rake angle along the cutting edge, which control the cutting force and chip formation, are discussed. In addition. a cutting model and energy method. in which elemental chip at each point on the cutting edge is described by simple shear plane oblique cutting model and the condition of side-curl of the chip is considered. is extended to drilling with the drills. In the analysis, it is assumed that the chip produced with whole cutting edge consisting of the main cutting edge and the cutting edge at the drill center can be expanded to be a plane. Two cases for chip separating or no chip separating at the junction of the main cutting edge and the cutting edge at the drill center are treated and discussed. Predicted result shows that Stabler's chip flow rule does not hold for the curved cutting edge drills.
