A surgical tool for use in a system for removing bone from vertebrae to relieve stenosis is provided. In one embodiment, the surgical tool includes a drill bit having a proximal end and a distal end, a drive shaft having a proximal rod portion and a distal tubular portion, the drill bit and the drive shaft configured to rotate about a horizontal axis in a clockwise direction; and an engagement system disposed between the drill bit and the drive shaft; wherein the engagement system is configured to selectively engage the drill bit to the drive shaft for powered rotation when the drill bit contacts a first material at a first predetermined resistance and to disengage the drill bit from the drive shaft when the drill bit engages a second material at a second predetermined resistance; and wherein the first predetermined resistance is greater than the second predetermined resistance.