A drill bit includes a cutter rod (1), the knife rod has a tip tip two is located in a main plane (C - C) on the cutting insert (5, 5 '), the cutting blades (5, 5') have in common plane (E - E second) on orientation of the short blade cutting center. The cutting edge forms a point central cutting edge for entering the work piece, and thus the drill bit is right. The knife

Bar, Two Flutes (6, 6 '), the chip groove (6, 6) extending from the tip to the end. In any section along the bar, the flutes are located are diametrically opposed to each other's position in the flat tube, flat tube and two common edge edge in the pipe on both sides of the belt plane (F F) 90 degrees extension, wherein the knife rod has a maximum in the rigid plane. The orientation of the second plane (E E) of the central cutting edge is approximately 90 degrees to the bottom end of the edge of the cutting edge plane or the bottom end of the tool bar (F - F).

A condition that can alleviate the sudden change of the state of the drill in the drilling operation of the concrete and the like, so that the drilling operation is stable, even when the chip is produced, the drilling efficiency is not reduced.

The Department is roughly cutting blade radial configuration, with at least 2 main cutting edge part, and in the circumferential direction with arranged between the main cutting edge and the cutting edge of the at least two side cutting edge of the cutting edge part is provided with a cutting edge as its cutting blade in the end, the main cutting edge is located in the center of rotation, the outer edge of the outer end of the rotation trajectory at the cutting edge part.

The side cutting edge part has side cutting edge as its cutting edge, the side cutting edge in end is positioned on the outer diameter side from the center of rotation of the outer part of the outer end of the rotation trajectory is located in the center of rotation to deviate from the side cutting edge portion of the position.

A drill bit, a plurality of cutting edges arranged on the front end of the drill bit, and a shaft shaped drill bit body which is arranged on the base end of the cutting edge and is formed on the base end;

The cutting edge part has a cutting edge cutting surface and the gap after edge forward end side protrudes formed by the cutting edge from the center of rotation of the outer diameter side drill lateral configuration is approximately radial;

The compound action by rotating motion and axial direction of the action of impact cutting, which is characterized in that the cutting edge has at least 2 main cutting edge part, and is arranged in the circumferential direction of the main cutting edge and the cutting edge of the at least 2 side cutting edge part;

The main cutting blade has the cutting edge as its cutting edge, the cutting edge in the end is located in the center of rotation, the outer edge of the outer end of the rotation trajectory is located in cutting edge, the side cutting edge part has side cutting edge as its cutting edge, the cutting edge is located in the inner end side from the center of rotation of the outer diameter side away from the site, located in the outer end of the rotation trajectory from the outer edge of cutting edge portion of the rotating center deviation side position.