Abstract: 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.

Abstract: 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.

Abstract: Disclosed is a high speed-perforating apparatus 1 comprising a rotor 17 into and through which a cylindrical rotary shaft 11 is integrally inserted, a stator 18 disposed around the outer periphery of the rotor 17 and a core bit 13 which is directly connected to the head end portion of the rotary shaft. A bit 15 having an outer diameter of up to 40 mm and a cutting edge thickness of less than 2 mm is used for the core bit 13. Perforation is carried out by the core bit 13 which is rotated at a high speed of 4000 rpm or more by a direct motor 2 comprising the rotor 17 and the stator 18. A perforating time can be greatly shortened by rotating the core bit at high speed.