DRILL

PROBLEM TO BE SOLVED: To provide a drill with high rigidity and high performance for ejecting chips. SOLUTION: The drill 1 includes: a shaft portion 20 rotatable on an axis; a pair of flute portions 21a, 21b helically extended on the shaft portion 20, and arranged at positions rotated 180° from each other on the rotation axis of the shaft portion 20; a chisel portion 22 arranged on the distal end of the shaft portion 20; a pair of inner blades 23a, 23b placed on the chisel portion 22; and a pair of outer blades 24a, 24b, in continuation from the radial outer ends of the inner edges 23a, 23b, respectively, and extending along the end surfaces 210a, 210b directed in the rotation direction of the flute portions 21a, 21b. The drill 1 has a cutting blade ratio (L1/L2) in the direct sight view of ≥0.50 and ≤0.60 when the inner blades 23a, 23b and the outer blades 24a, 24b are viewed from the perpendicular direction, and a chisel angle θ1 of ≥145° and ≤149°. COPYRIGHT: (C)2011,JPO&INPIT