Predictive Models for Drilling Thrust and Torque — a comparison of three Flank Configurations

Predictive models for drilling thrust and torque are presented and compared for three drill flank configurations. The models are based on the mechanics of cutting analysis, fundamental machining data such as the shear stress and chip length ratio as well as the flank configuration which affects the basic tool angles like normal rake at the chisel edge region. The three flank shapes investigated are the ‘Plane Flank’, the popular ‘Conical Flank’, and the Clearance planes flank'. The effects of feed, speed and prominent drill point geometrical features on the predicted thrust and torque resulted in plausible and comparable trends for the three flank shapes. The differences in predictions between the ‘conical flank’ and the other two flank models has also been shown to be small for the work material tested. In addition, good correlation between predicted and experimentally measured thrusts and torques has been found for a wide range of conditions. It is shown that provided the basic geometry at the drill cutting edges can be estimated, the more complex drill flank analyses are not essential for adequate thrust and torque predictions when using the drilling analysis presented.