Sensing arrangements for a handpiece sense suction pressure or fluid flow within a suction path to determine the position of a movable cutting element relative to a fixed cutting element of a cutting accessory. A controller calculates actual speed of the movable cutting element from measured pressure or measured fluid flow. The cutting elements have openings that, when aligned, form a window. The controller controls power to a motor that drives the cutting element. When the handpiece is deactivated, the controller stops the movable cutting element at a predetermined position to close or partially close the window. The controller controls the cutting speed in view of joint pressure combined with suction pressure, or in view of fluid flow through the suction path, to maintain an optimal fluid flow rate that enhances the cutting action of the cutting accessory. Pressure or flow sensors may detect a clog in the suction path.