Drill speeder for machine tools

摘要

An electric motor driven drill and a battery therefor are mounted within a toolholder for a machine tool. The battery is coupled to the motor through a centrifugal switch which closes when the toolholder is rotated about its axis above a predetermined speed and opens when the rotary speed of the toolholder falls below the predetermined speed. The toolholder is mounted in the spindle of a machine tool and the drill turns on when the spindle is rotated and turns off when the spindle stops, the rotary speed of the spindle being added to the rotary speed of the drill in one direction of spindle rotation and subtracted from the rotary speed of the drill in the opposite direction of spindle rotation.