SOME FUNDAMENTAL AND PRACTICAL ASPECTS OF TWIST DRILLS AND DRILLING

In this paper the basic design geometry, specification, point sharpeni ng, geometrical variability and control during manufacture, cutting ac tion and performance prediction models of twist drills will be reviewe d in the light of findings from the author's research group and elsewh ere. It is shown that twist drills are subject to ambiguities in their design geometry and specification as well as to large geometrical var iability within and between manufacturers which adversely affect the p redictability of drill performance and the efficiency of the drilling process. Possible research and drill manufacturing strategies aimed at establishing twist drills and drilling performance on a sound scienti fic, quantitative and predictive basis as well as taking full advantag e of modern computer-based manufacturing capabilities are briefly disc ussed.