| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method for working by which chipping of a workpiece is reduced and the drill life is prolonged. SOLUTION: This method for perforating comprises cutting a drill 1 into a boardlike material while making the axis of the drill 1 perform a circular motion. The drill 1 comprises a truncated conical tip part 1a, a circular cylindrical base part 1b, etc. The diameter of the top surface of the tip part is 3-30 deg. expressed in terms of taper angle and the height of the truncated cone is 50-120% of the board thickness of the boardlike material. The diameter of the base part is 20-80% of the hole diameter.</p> |
