| 摘要 |
A cutting tool including an improved centripetal property and rigidity is provided. The cutting tool includes a drill body rotating about an imaginary rotational axis, and a cutting portion located at a leading edge side of the drill body, wherein the cutting portion includes a first grinding face including a first chisel edge radially extending from the rotational axis and a second chisel edge radially extending from the rotational axis and defining a predetermined angle with the first chisel edge, a second grinding face including a third chisel edge disposed to be point-symmetrical to the first chisel edge in terms of the rotational axis and a fourth chisel edge disposed to be point-symmetrical to the second chisel edge in terms of the rotational axis, a first relief face radially extending from the first chisel edge and the fourth chisel edge and including a first cutting edge formed at a front of a rotation direction of the drill body, a second relief face meeting a rear of the rotation direction of the first relief face, a third relief face radially extending from the second chisel edge and the third chisel edge, including a second cutting edge positioned at the front of the rotation direction of the drill body and disposed to be point-symmetrical to the first relief face in terms of the rotational axis, a fourth relief face meeting the rear of the third relief face in the rotation direction, a first intersection line formed along a boundary where the first relief face and the second relief face meet, and a second intersection line formed along a boundary where the third relief face and the fourth relief face meet, wherein the first intersection line and the second intersection line are spaced apart from an imaginary center line passing the rotational axis, the first relief face and the third relief face. |
