A powered surgical tool system comprises a surgical handpiece including a brushless, sensorless motor having a plurality of windings and a rotor a coupling assembly that is configured to releasably hold a cutting accessory to the handpiece and means configured to determine the position of the rotor and to selectively apply energization signals to said motor windings based on the position of said rotor. The means are configured to, when the motor is at a speed at or below a threshold speed, determine the position of the motor rotor based on inductance sensing of the position of said rotor and, when the motor is at a speed above the threshold speed, determine the position of said motor rotor based on a process other than inductance sensing.
