A Novel Approach to the Design of Self-Piloting Drills With External Chip Removal, Part 1: Geometry of the Cutting Tip and Grinding Process

The performance of a self-piloting drill with external chip removal is affected by the geometry of its cutting tip. A comprehensive analysis of the cutting tip geometry and its influence on the drill performance is made. This subject is treated in two parts. In Part 1, the cutting tip geometry is analyzed. Special attention is given to the flank planes and a novel approach to the design of the drill was developed. By this approach the drill flank planes are located with minimum offset of the supporting pads’ faces relative to the plane of the drill corner’s rotation. Since several important drill angles are defined, the analysis is extended to cover the grinding process. The experimental comparison between the ordinary and newly designed self-piloting drills with external chip removal is also made to show the advantages of the latter.