TWO-BLADE DOUBLE MARGIN DRILL

PROBLEM TO BE SOLVED: To enable an interval between a main margin and a sub-margin to fall within an ideal range, by shortening an axial directional length as much as possible up to the sub-margin from the main margin of a two-blade double margin drill.SOLUTION: An interval between the main margin 6 and the sub-margin 7 provided on the outer periphery of a land part 5 is set to 80°-100°, both flanks 8 are also constituted of a second flank 8a and a third flank 8b of a plane, a thinning part 4 having a thinning surface 4a of a convex circular arc is formed in the rotational direction of a drill in a drill front view in a tip center part, and the outer end in the radial direction of the thinning surface 4a is arranged in the rear in the drill rotating direction more than the tip of the sub-margin 7 and is made to reach the outer periphery of the land part 5.