US Patent 7350595 Drilling device and drilling method

A drilling device is composed so as to drill a drilled object composed of a brittle material with the end of a rotating core bit by using a core bit in which a bit, formed by dispersing and arranging a cemented carbide or super abrasive in a binder phase, is provided on the end of a cylindrical tube, and rotating the core bit around an axis with a direct motor. The drilling device is composed so that the core bit is rotated such that the peripheral velocity at the outer periphery of the bit is 300 m/min or more while the core bit presses against the drilled object at a pressure of 0.6 N/mm2 or more during drilling.