Patent ID: 9162371
Filing Date: 2015-10-20
Classification: B23B,B28D,E21B,Y10T

Abstract:
1. A drill bit comprising: a bit tip including at least three cutting edge portions which are arranged radially in a circumferential direction at a distal end of the bit tip, each cutting edge portion having a rake face and a relief face forming a joint ridge serving as a cutting edge; and a bit shaft having a distal end face integrally attached to a proximal end face of the bit tip such that the bit shaft rotates integrally with the bit tip, wherein the bit shaft includes a dust suction passage extending in a longitudinal direction of the bit shaft, such that a distal end of the dust suction passage extends to a distal end portion of the bit shaft and a proximal end of the dust suction passage is in communication with a suction device; wherein the distal end portion of the bit shaft includes a dust suction auxiliary passage, such that the dust suction auxiliary passage extends from the dust suction passage in a radially outward direction orthogonally to the dust suction passage, and a radially outer end of the dust suction auxiliary passage is open at an outer peripheral face of the bit shaft; wherein the dust suction auxiliary passage is formed in such a manner that a groove is formed at the distal end face of the bit shaft, the groove having a portion opening at the distal end of the bit shaft and a portion opening at the outer peripheral face of the bit shaft, and the portion opening at the distal end is blocked by the proximal end face of the bit tip; and wherein a recess having a shape corresponding to a shape of the proximal end face of the bit tip and accommodating a proximal end portion of the bit tip is formed at the distal end face of the bit shaft such that, when the bit tip is accommodated in the recess, the groove is positioned between cutting edge portions that are adjacent to each other in a circumferential direction.