The standard twist drills with curved edges are thoroughly studied in the light of a newly developed technique of displaying and analyzing space angles on cutting tools in a projection plane [1, 2]. The study leads to a full understanding of the relations between the drill point shape and the cutting angle distributions. The study reveals that there exists a special edge line that insures the rake angle at each point reaching its maximum. The technique of optimizing cutting edge shape of a twist drill to realize a desired rake angle distribution is presented. Ways of designing and grinding the flank in order to control the clearance angle are also suggested. Computer software for calculating edge shape from given cutting angle distribution (and vice versa) is developed with the computation results shown. The fundamentals of the study are described, the theoretical and experimental work are presented.

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