| 摘要 |
PROBLEM TO BE SOLVED: To provide a drill for immediately relaxing the danger of unstable regeneration effect at the time of starting use, that is, for reducing the vibration amplitude of the drill handle in drilling work. SOLUTION: In a drill equipped with a handle, a groove for transporting at least one spiral chip, and a drill bit equipped with at least one cutting blade 5 to be arranged between the front surface or upper surface 6 and a flank 7, the flank is extended by forming a given angle to a reference surface crossing the center spindle of the drill handle. A second flank is provided at least part of the cutting blade 5, and extends at another angle to the reference surface than the flank 7. |
