Patent ID: 7909549
Filing Date: 2011-03-22
Classification: B23B,Y10T

Abstract:
1. A small-diameter deep hole drill having a drill diameter of 1 mm or less, including a drill section having cutting edge(s) and flute(s), wherein said flute has a length which is at least 5 times and at most 10 times the drill diameter; said drill section at first shrinks and then expands in diameter, changing said drill diameter from a drill cutting edge toward a rear end of the drill section, an outer diameter of the drill section at the end of said flute is at least 0.9 times and at most 0.98 times the drill diameter; an expanded-diameter portion is provided between said drill section and a neck section, having a diameter which expands from the outer diameter of the end of the flute up to 1 or less times the drill diameter; said neck section is connected with a shank section and has a diameter smaller than the drill diameter and a length which is 10 or more times the drill diameter.