A surgical drill for actuating a drill bit , the surgical drill including: a housing ; a motor disposed in the housing; a rotor that is rotatably disposed in the housing and that is part of or connected to the motor so the actuation of the motor results in the rotation of the rotor, the rotor having opposed proximal and distal ends; a coupling assembly disposed in the housing, the coupling assembly being adapted to releasably couple a drill bit configured to form a bore in living tissue to the rotor so that the drill bit rotates upon rotation of the rotor; a probe , the probe being slidably mounted to the housing so as to extend forward from the housing, the probe having a distal end adapted for placement against tissue; and a transducer assembly mounted to the housing for producing a signal representative of the distance the housing moves relative to the distal end of the probe when the drill bit is advanced into tissue; wherein the rotor is formed with a bore dimensioned to receive a proximal section of the drill bit and a proximal section of the probe ; the coupling assembly is located in the housing adjacent the proximal end of the rotor so that, when the drill bit is coupled to the motor rotor , a proximal section of the drill bit is coupled to the proximal end of the rotor and the drill bit extends through the rotor bore and the drill bit extends forward out of the distal end of the rotor towards the tissue against which the drill bit is to be applied; and the probe is mounted to the housing so as to have a proximal section that is able to move longitudinally in the bore of the rotor and a distal section that extends forward of the rotor so as to be located adjacent a distal end of the drill bit . a housing ; a motor disposed in the housing; a rotor that is rotatably disposed in the housing and that is part of or connected to the motor so the actuation of the motor results in the rotation of the rotor, the rotor having opposed proximal and distal ends; a coupling assembly disposed in the housing, the coupling assembly being adapted to releasably couple a drill bit configured to form a bore in living tissue to the rotor so that the drill bit rotates upon rotation of the rotor; a probe , the probe being slidably mounted to the housing so as to extend forward from the housing, the probe having a distal end adapted for placement against tissue; and a transducer assembly mounted to the housing for producing a signal representative of the distance the housing moves relative to the distal end of the probe when the drill bit is advanced into tissue; wherein the rotor is formed with a bore dimensioned to receive a proximal section of the drill bit and a proximal section of the probe ; the coupling assembly is located in the housing adjacent the proximal end of the rotor so that, when the drill bit is coupled to the motor rotor , a proximal section of the drill bit is coupled to the proximal end of the rotor and the drill bit extends through the rotor bore and the drill bit extends forward out of the distal end of the rotor towards the tissue against which the drill bit is to be applied; and the probe is mounted to the housing so as to have a proximal section that is able to move longitudinally in the bore of the rotor and a distal section that extends forward of the rotor so as to be located adjacent a distal end of the drill bit . <EOS>