| 摘要 |
PROBLEM TO BE SOLVED: To provide a twist drill having an oil hole capable of ensuring the sufficient feed quantity of a cutting fluid. SOLUTION: In the oil hole 7 comprising a main pipe 8 and a branch pipe 9, the main pipe 8 is formed of two stop holes cut parallel to the axis of rotation from a rear end to a forward end of a drill body, and the branch pipe 9 is formed of a communication hole of the forward end of the drill body with the main pipe 8. The main pipe 8 is formed in a thick wall part away from a web part at the drill center, and set at the position so as not to pierce two twisted chip discharge grooves 4. Sufficient feed of the cutting fluid can be ensured by two main pipes 8, and both the main pipes 8 and the branch pipe 9 have a shape to be easily formed.
|
