| 摘要 |
PURPOSE:To bore a combined material of complex material and metal with high accuracy by constructing the tip portion of drill with a primary cutter having tip shape of metal drill and a flat secondary cutter continuous to the primary cutter and having smaller tip angle than that of the primary cutter. CONSTITUTION:Tip portion 11 of drill 10 is constructed with a primary cutter 11A and a secondary cutter 11B formed continuously thereto. The primary cutter 11A has same tip shape as that of metal drill, while the secondary cutter 11B has flat shape known as dagger drill. When complex material and metal are bored under overlapped condition, metal is bored first by the primary cutter 11A followed by boring of complex material, and delamination at the outer circumference of hole is removed precisely through subsequent boring with the secondary cutter 11B around the primary hole. When cutting quantity of secondary cutter 11B is set considerably lower than that of the primary cutter 11A, abrasion of metal due to the secondary cutter 11B can be suppressed.
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