Analysis of the high performance drilling process: Influence of shape and profile of the cutting edge of twist drills

The aims of the investigations presented in this paper were. to measure the tool load under conditions of high petformance drilling and to analyze if changes of the tool edge shape as well as the edge profile significantly influence the edge stresses. The described methods to analyze the influences of edge shape modifications will contribute to the optimization of drilling tools. Based on a specific cutting edge shape of a drilling tool, systematic changes to the tool's chamfer and the transition from the chisel edge to the cutting edge were made. Forces and temperatures on the cutting edge were measured as well as the heat flow into the chips and the workpiece. Using a quick-stop device, chip roots of the different drill tools under conditions of high performance machining were made in order to analyze the chip formation. The contact between chip and rake face could be made visible by a so called contact area analysis. It could be shown that the modification of the transition from the chisel to the cutting edge influences the orientation of the forces on the drill. Machining with a rounded cutting edge shape compared to a chamfered edge reduces the mechanical and thermal tool load. This is confirmed by the fact that the deformation zone in front of the cutting edge is smaller as shown by the crosssections of the chip roots. The presented experimental methods show the possibility of determining influences of modified cutting edge shapes and to adapt the drill to the needs of the high performance drilling.