| 摘要 |
PROBLEM TO BE SOLVED: To provide a drilling tool free to use for a long period of time and easy to exchange a central drill by providing a holding means extending in the inside of a lateral hole in a region of a central hole and fixing and positioning the central drill. SOLUTION: A drill main body having a cutting bit is furnished on the drilling side, and a central hole 5 provided in the axial direction to receive a central drill 6 having a central drill shank 7 is furnished. Thereafter, a holding means 12 to fix and position the central drill 6 is furnished in a region of this central hole 5. This holding means 12 is extended by crossing the inside of a lateral hole 13 in the drilling direction and passes through the inside of the central hole 5 so as to meet its center with a central shaft of a drilling tool 1. Additionally, a hole 9 to correspond with the lateral hole 13 is provided on the central drill shank 7. Consequently, it is possible to provide the drilling tool 1 free to use for a long period of time and easy to change the central drill 6. |
