Air feed peck drill

Abstract

A pneumatic air feed peck drill adapted to drill in repetitive cycles including a rapid advance phase, a slower drilling phase, and a rapid retract phase. The rapid advance phase ends and the drilling phase begins at a set back position, an adjustable distance from the workpiece, to minimize a drill bit and workpiece damage. The drill includes a drill motor and feed cylinder powered by air to rotate and advance and retract the drill motor. The drill motor and feed cylinder is coupled with an air and mechanical control system including a hydraulic feed control unit having a piston rod coupled with the drill motor to dampen the advance of the drill motor during the drilling phase and to release for rapid retract and advance phases. A brake is mounted for control of the feed control unit piston rod to releasably engage the piston rod during the retract phase to limit the movement of the rod to an adjustable set back distance controlled by a set back nut limiting the distance the brake may move relative to the feed control unit when the brake engages the piston rod. A pneumatic system including a volume chamber is coupled with the air system to control the peck cycle rate. One embodiment of the drill includes an auxiliary thrust and retract piston assembly while another embodiment has only the primary drill motor and feed cylinder.