SMALL-SIZED DRILL

摘要

PROBLEM TO BE SOLVED: To provide a small-sized drill having high rigidity, good chip discharge performance and high hole position accuracy. SOLUTION: The side of a blade part is provided with one chip discharge groove 15. The outer periphery side rake angleθmade between the outer periphery side of a rake face 15a of a cutting blade 16 and the direction of a tangent A of the outer periphery is set within the range of 90 deg.<=θ<=145 deg.. The ratioα/βof a margin 17 to the outer peripheral surface except the chip discharge groove 15 of the blade part is set 10 to 100%.