Modeling and Experimental Verification of Torque and Thrust Forces Generated by the Conventional Drill’s Chisel Edge

As alternative to complex modeling, simple empirical equations that provide estimates of the chisel edge’s torque and thrust cutting force components are a useful tool for estimating chisel cutting forces. This work aim to develop a model capable of estimating torque and thrust forces generated by only the drill’s chisel edge as function of machining feed (f), cutting velocity (V), and chisel edge’s width (w). The chisel edge’s generated machining forces are quantified and statistically verified utilizing JMP-SAS/STAT^® design of experiment (DOE) software. An experimental setup involving 50 drilling tests was conducted with drilling feed, spindle speed and chisel web dimensions varied to enhance the statistical significance of the collected data. Experimental torque and thrust data were collected using a 4-channel rotary dynamometer (Kistler model 9123) at a 200 Hz sampling rate. Torque and thrust values encountered at the chisel edge were isolated from those of the full drill. Due to its wide industrial use, the workpiece material investigated is Aluminum 6061-T6. In-line with literature, reported values of experimentally collected data showed that chisel edge’s forces increased with drilling feed and drill bit web dimension while decreased with increasing speed (perhaps due to thermal softening). JMP-SAS/STAT^® module, nonlinear fitting with convergence criteria of 10⁻¹⁵ and 70 iterations was utilized The developed model equations allow the estimation of the forces encountered at the chisel edge of a classical twist drill while cutting aluminum alloy 6061-T6 material.