Abstract: A drill capable of performing high-quality drilling machining on a material which is hard to be cut such as CFRP is provided. The drill includes a drill body 4 having a shank portion 2 at a rear side of the drill main body and a cutting portion 3 at a front side of the drill main body, a first land A to a fourth land D at the cutting portion 3, a first cutting portion groove 5a to a fourth cutting portion groove 5d provided between the lands of the first land A to the fourth land D, a pilot blade 6 formed at the tip of the cutting portion 3, a diameter-enlarging spiral thread portion 9 continuously following the pilot blade 6, a finished spiral thread portion 12 continuously following the diameter-enlarging spiral thread portion 9, a diameter-enlarging spiral blade portion 18, and a finishing spiral blade portion 19.

Abstract: A drill capable of performing high-quality drilling machining on a material which is hard to be cut such as CFRP is provided. The drill includes a drill body 4 having a shank portion 2 at a rear side of the drill main body and a cutting portion 3 at a front side of the drill main body, a first land A to a fourth land D at the cutting portion 3, a first cutting portion groove 5a to a fourth cutting portion groove 5d provided between the lands of the first land A to the fourth land D, a pilot blade 6 formed at the tip of the cutting portion 3, a diameter-enlarging spiral thread portion 9 continuously following the pilot blade 6, a finished spiral thread portion 12 continuously following the diameter-enlarging spiral thread portion 9, a diameter-enlarging spiral blade portion 18, and a finishing spiral blade portion 19.