Importance

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Abstract

An object is to provide a drill bit with improved strength of joint between a bit tip and a bit shaft without diminishing dust suction performance of the drill bit. A drill bit 1 includes: a bit tip 3 including at least three cutting edge portions arranged at the distal end of the bit tip 3 such that they are spaced apart from each other in a circumferential direction, each cutting edge portion 3c having a rake face 3s and a relief face 3e forming a joint ridge L1 serving as a cutting edge; and a bit shaft 2 having a distal end face 2F welded to a proximal end face of the bit tip 3 such that the bit shaft 2 rotates integrally with the bit tip 3. The bit shaft 2 includes a dust suction passage 4 extending in the longitudinal direction of the bit shaft 2, such that the distal end of the dust suction passage 4 extends to a distal end portion of the bit shaft. A dust suction auxiliary passage 6 is formed at the distal end portion of the bit shaft 2, such that the dust suction auxiliary passage 6 extends from the dust suction passage 4 orthogonally or substantially orthogonally to the dust suction passage 4, and a radially outer end 6t of the dust suction auxiliary passage 6 is open at an outer peripheral face 1F of the bit shaft 2. A proximal end portion 3b of the bit tip 3 is integrally attached to the distal end face of the bit shaft 2.

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First Claim