Invention Grant
US4796319A Combination screw-tapping and screwdriving tool 失效
组合螺丝攻螺丝刀

Combination screw-tapping and screwdriving tool
Abstract:
A drill accessory kit for mounting screw-type fasteners is comprised of several drill bit holders and a screwdriving attachment. The bit holder engages a common twist drill bit in the chuck of a drill and allows one to drill a pilot hole to a desired depth in a workpiece with a cutting action which provides a proper-shaped hole for clean flush mounting or countersinking of a screw. Subsequently, the screwdriver attachment slips over the drill bit and engages with the bit holder, allowing a quick change from drilling to powerdriving of a screw.
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