| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-stage type drill for drilling a multi-stage hole. SOLUTION: This multi-stage type drill includes a shank and a drill body, which are integrally formed. A free end is provided on the lower end of the drill body, a plurality of grooves penetrating the free end are formed on the outside, a force receiving surface is formed on one side of the groove, a plurality of step parts gradually increased in diameter are provided on the free end, and the step part is provided with at least one blade part. COPYRIGHT: (C)2007,JPO&INPIT
|
