| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill capable of performing penetration drilling with high quality in one step without the occurrence of burrs or delamination in a workpiece material while achieving effect of suppressing a drilling heat.SOLUTION: A drill 1 for a composite material has: a tip end with a tip cutting edge 5 formed thereon; a tapered part 4 formed continuously to the rear end side of the tip end, and also formed in a tapered shape with a diameter difference between the outside diameter on a tip side and the outside diameter on the rear end side having a diameter larger than the outside diameter of the tip side; and a straight part 3 formed continuously to the rear end side of the tapered part 4 and formed in the same diameter as a whole so as to form a finishing diameter equal to or more than the outside diameter on the rear end side of the tapered part 4. A spirally-twisted main blade 7 is formed in the outer circumference of the tapered part 4 and is set so that a drilling diameter becomes larger continually, and an auxiliary blade 10 is formed in an outer circumference land surface 12. |
