Computer‐Aided Geometrical Analysis of the Fluting Operation for Twist Drill Design and Production. I. Forward Analysis and Generated Flute Profile

Abstract

A computer‐aided ‘forward’ analysis, based on a typical automated flute grinder used in drill production, has been developed to study the flute generation process and the intended or design flute profile of twist drills. It has been shown that the flute grinder involved three machine setting variables and seven wheel profile variables for generating the flute for each drill specification. Based on the recommended wheel profile and machine settings, the forward analysis has shown that 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. Furthermore, these numerical simulation studies have shown that the intended or design lip flute profile closely approximated the ideal profile for straight lip production while the heel profile closely approximated a parabolic curve tangential to the core or web diameter and passing through the heel corner. Numerical simulation of the effect of the machine settings has shown that the wheel setting angle has to be set greater than the specified helix angle in order to avoid undercutting and generate the intended flute profile for straight lip production while the other setting variables had no major influence on the generated flute profile in practice. Apart from clarifying longstanding ambiguities in the geometry and specification of flute profile of twist drills, this investigation has provided essential information for the development of the ‘backward’ analysis considered in the next paper.