Abstract

A reversible drill, equipped with a chuck having a jaw guide, chuck jaws constrained by the jaw guide for radial advancement and retraction, and chuck jaw propulsion means for driving the chuck jaws in advancement and retraction, is equipped with a manually actuable clutch for easing the chuck jaw propulsion means into and out of engagement with the drill housing to, respectively, prevent and allow relative rotation between the jaw guide and the chuck jaw propulsion means. When the drill motor is driven in one direction of rotation, the chuck jaw propulsion means is immobilized relative to the drill housing and the chuck jaws are advanced radially toward each other to grip a drill bit. When the housing and chuck jaw propulsion means are eased together and the drill motor is driven in the opposite direction, the chuck jaw propulsion means is immobilized and draws the chuck jaws apart as the jaw guide rotates to release a drill bit. When the chuck jaw propulsion means is disengaged from the drill housing the drill is operable in a normal manner. An O-ring is positioned between the drill housing and the chuck jaw propulsion means and is operable independently of the clutch mechanism to exert a light drag on the chuck jaw propulsion means. Drill bits can be lightly seized and chuck jaws opened without engagement of the clutch mechanism.