Computer-Aided Modelling of the Fluting Process for Twist Drill Design and Manufacture

Abstract

Computer-aided models of a typical flute grinder, incorporating both ‘forward’ and ‘backward’ analyses, are outlined and used to simulate the flute grinding process and study the intended or design flute profile of twist drills. Based on recommended wheel profile and flute grinder settings, the ‘forward’ analysis has shown that the generated lip flute profile closely approximated the ideal profile for straight lip production while the heel flute profile approximated a parabolic curve. Furthermore the flute profile was partly generated by the ‘envelope’ of the wheel profiles and partly by the locus of the point of discontinuity on the wheel profile. The effects of the wheel profile and machine settings on the generated flute profile have been studied. The ‘backward’ analysis, based on the ‘contact curve’ method, has shown that only portions of the required wheel profiles to generate the given ‘design’ drill flute profiles were physically feasible so that the generated flute profiles are only good approximations of the design flute profiles. The use of these computer models in drill design and manufacture are also discussed.