A Study on Curved Edge Drills
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Standard twist drill, under the standard grinding its flank, has a pair of straight major edges. Various new re-sharpening methods, including Qun-drill, however, break the “straight edge” restrictions, re-sharpening the major cutting edges of standard twist drill into a variety of curves to improve its drilling performance. This chapter, with the help of previously introduced method of mapping space angles onto a projective plane, made an in depth study on the cutting edge shape of twist drill, cutting angle distribution along the curved cutting edge and the relationship between cutting edge shape and drilling performance. Study reveals: there is a special cutting edge allowing the rake at each point on it reaches the possible maximum value at the point, thus enabling significantly improved machining ability. This chapter provides the technology for optimizing cutting edge shape to obtain desired rake angle distribution, as well as the technology through the drill flank design and grinding in order to control distribution of drill clearance. Theoretical analysis and experimental research have been performed. Computer software was developed, so that the cutting edge shape realizing required rake angle distribution is calculated.