Drill and method for forming hole

摘要

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.

主权项

1. A drill comprising:
a drill main body having a shank portion at a rear side of the drill main body and a cutting portion at a front side the drill main body; a group of lands including a first land to an n-th land formed at the cutting portion; a group of cutting portion grooves including a first cutting portion groove to an n-th cutting portion groove, each of the cutting portion grooves being formed between two adjacent lands from the group of lands; a pilot blade which is formed at a tip of the cutting portion and forms a pilot cutting hole in a material to be machined; a diameter-enlarging spiral thread portion having a group of threads of a diameter-enlarging spiral thread which is formed on each of the first land to the n-th land of the group of lands so as to continuously follow the pilot blade, the diameter-enlarging spiral thread gradually forming a spiral convex part while cutting the pilot cutting hole so as to enlarge a diameter of the pilot cutting hole; a finishing spiral thread portion having a group of threads of a finishing spiral thread which is formed on each of the first land to the n-th land of the group of lands so as to continuously follow the diameter-enlarging spiral thread portion, each of the finishing spiral thread having the same height, and cutting and finishing the spiral convex part so as to have a flat wall surface; a spiral dent formed between a spiral thread and a spiral thread of the diameter-enlarging spiral thread and the finishing spiral thread in a way that each adjacent cutting portion groove from the group of cutting portion grooves can communicate with each other; a diameter-enlarging spiral blade portion which is a crest edge of the diameter-enlarging spiral thread formed by the diameter-enlarging spiral thread and a groove surface of each of the first cutting portion groove to the n-th cutting portion groove of the group of cutting portion grooves and has a group of blades of a diameter-enlarging blade, the diameter-enlarging blade performing a segmented diameter-enlarging cutting or a split diameter-enlarging cutting to the pilot cutting hole formed by the pilot blade; and a finishing spiral blade portion which is a crest edge formed by the finishing spiral thread and a groove surface of each of the first cutting portion groove to the n-th cutting portion groove of the group of cutting portion grooves and has a group of blades of a finishing blade, the finishing blade performing a segmented diameter-enlarging cutting or a split diameter-enlarging cutting to a diameter-enlarging culling hole formed by the diameter-enlarging spiral blade portion.