Abstract: The present invention provides a method of drilling a hole in a workpiece in order to control breakthrough of the workpiece comprising the steps of: a) initiating contact between a drill bit of a drill unit and the workpiece; b) operating the drill unit to rotate the drill bit to drill the workpiece; c) during drilling of the workpiece measuring the force, F and torque, T, experienced by the drill bit; d) calculating a variable F?, based on the measured force, F, representing the rate of change of F; e) calculating a variable, T? based on the measured torque, T, representing the rate of change of T; f) calculating a variable F? representing the rate of change of F?; g) calculating a variable T? representing the rate of change of T?; h) detecting the onset of breakout of the workpiece by use of the variables F?, F?, T? and T?; i) thereby controlling the speed of rotation of the drill bit during breakthrough of the workpiece to control the degree of breakout of the drill bit from the workpiece.

Abstract: The present invention provides a method of drilling a hole in a workpiece in order to control breakthrough of the workpiece comprising the steps of: a) initiating contact between a drill bit of a drill unit and the workpiece; b) operating the drill unit to rotate the drill bit to drill the workpiece; c) during drilling of the workpiece measuring the force, F and torque, T, experienced by the drill bit; d) calculating a variable F?, based on the measured force, F, representing the rate of change of F; e) calculating a variable, T? based on the measured torque, T, representing the rate of change of T; f) calculating a variable F? representing the rate of change of F?; g) calculating a variable T? representing the rate of change of T?; h) detecting the onset of breakout of the workpiece by use of the variables F?, F?, T? and T?; i) thereby controlling the speed of rotation of the drill bit during breakthrough of the workpiece to control the degree of breakout of the drill bit from the workpiece.