The combined influence of various design and process parameters of gundrilling on tool life: experimental analysis and optimization

This paper examines experimentally the combined influence of various design and regime parameters in gundrilling on tool life. Cutting speed, feed, approach angles, flank angles and vertical shifts of the outer and inner cutting edges, location of the drill point are included into consideration. It is demonstrated that tool life is a complex function of not only each of the considered parameters alone but also of their combinations. The Hooke and Jeeves method has been used to optimize the geometry of gundrills by the criterion of tool life. It is shown that understanding the most essential system relationships in the drilling process allows the adjusting of the regime and design parameters of gundrilling to achieve not only the maximum tool life, but also chip breakability and highest feed (productivity).