DOUBLE DRILL BIT

Abstract

The design refers to the main and auxiliary drill bits, including, and the width and angle of the inverted positions of the cutting edges of the drill bits can be set by adjusting the cutting edge positions of the main and auxiliary drill bits. The double drill (1) includes the main drill (2) and the auxiliary drill (3). The carbide tips (7, 9, 14), and (15) with protruding shapes in the drilling direction are positioned at least at the top and bottom of the base (4), and (13) of each main and auxiliary drill. The protruding tip of the carbide tip of the auxiliary drill is placed behind the protruding tip of the carbide tip of the main drill in the drilling direction. The protruding tip of the main drill (2) is placed closer to the hole wall or pile core direction, or is placed at the center, hole wall and pile core direction perpendicular to the excavation direction.The protruding tip of the auxiliary drill bit (3) is placed closer to the hole wall direction or the pile core direction, or is placed at the center, the hole wall direction and pile core direction perpendicular to the excavation direction.