| 摘要 |
<p>A boring device, wherein a bit formed by distributedly disposing ultra fine abrasive grains in a binder phase formed by sintering a binder material is fitted to the tip of a cylindrical tube to form a core bit, the core bit is drivingly rotated around the axis thereof by a direct motor to bore a bored object formed with a brittle material by the tip of the rotating core bit, and the core bit is rotated so that, with the core bit pressed against the bored object with a pressure of 0.6 N/mm2 or higher at the time of boring, the peripheral velocity of the bit on the outer peripheral side is 300 m/min. or faster.</p> |
