an apparatus is described that converts a manual adjustment procedure of a lathe on an existing pulp - grinding machine into an automated electronic procedure . the pre - existing lathe has a sharpening burr affixed to a movable plunger . the plunger is manually lowered by a hand crank until the burr contacts a surface of a pulp - grinding stone . the present invention replaces the hand crank with a reversible , variable speed motor . a transducer is affixed to the plunger wherein electric signals are produced in response to vibrations resulting from contact between the burr and the grinding stone . the signals are processed by a standard programmable controller to control the motor . an electronic encoder electrically measures the position of the plunger and communicates the position to the programmable controller . when the burr on the plunger contacts the grinding stone , the motor is programmed to automatically stop . the controller can then direct the motor to move the plunger the precise depth required for a specific burr , prior to the lathe making a horizontal pass along the stone . the controller records the contact position of the plunger for the next sharpening procedure .