Calculation of main cutting edge forces and torque for drills with arbitrary point geometries

Abstract

A model for calculating main cutting edge torque, thrust, and radial force distributions for drilling gray cast iron with solid carbide and carbide-tipped drills is described. Unlike previous models, this model is applicable to arbitrary point geometries and includes radial forces due to point asymmetry. A general parametric method for characterizing complex point geometries is first described. Using this method, together with empirical cutting force models from end cutting tests, torque, thrust, and radial force calculations are carried out for ten representative drills covering a range of available geometries. Calculated and measured torque values agree to within the repeatability of the measurements. Calculated thrust force values are reasonable, but are significantly lower than measured values in most cases, since chisel edge contributions are not included. Calculated radial forces for an asymmetric drill agree with limited measured values to within twice the repeatability of the measurements. Future work on chisel edge contributions, temperature calculations, and force calculations for interrupted holes is briefly discussed.