| 摘要 |
PROBLEM TO BE SOLVED: To form a hole, too large to form a hole by a drill alone without adhering chips and cut disc to a piercing body for centering and besides generating burrs at the lower edge of a hole, in a synthetic resin plate through automation. SOLUTION: A tool comprises a cylinder blade body 1 provided at a cylinder end with a cutting edge 11; and a piercing body 2 for centering having a pointed part 21 concentrically situated in the cylinderical blade body 1 and further protruding axially externally than the cutting edge 11 and piercing a synthetic resin plate. This constitution prevents adhesion of chips and a cut disc to the piercing body 2 with generating chips by the piercing and forms a hole free from burrs and automates boring.
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