Drill screw having cutting edges each forming an arc curving to a head side.

摘要

A drill screw is composed of a drill portion (11) on a tip of the drill screw, a threaded portion (12) succeeding to the drill portion (11) and a head (13) succeeding to the threaded portion (12) whereby a ridge (14) on the threaded portion (12) threads into an inside wall of a hole while the drill portion (11) drills through a punctured object. The drill screw has cutting edges leading from both ends of a chisel positioned at the center of the tip of the drill screw. Each of the cutting edges forms an arc curving to a head side in an axial direction of the drill screw. Also, a shape of each of the cutting edges forms an arc curving to a back in a rotational direction of the drill screw.