| 摘要 |
<p>Disclosed is a drill bit which maintains dust attraction performance and has increased rigidity at a connection portion between a bit tip portion and a bit shaft portion; wherein the drill bit (1) comprises the bit tip portion (3) arranged with at least three cutting blade portions on the tip end in the peripheral direction at intervals so that a connecting ridge line (L1) between a rake face (3s) and a relief face (3e) of each cutting blade portion (3c) defines a cutting blade, and a bit shaft portion (2) welded on a base end face of the bit tip portion (3) so as to rotate together; and wherein the bit shaft portion (2) is provided with a dust attraction passage (4) extending in the longitudinal direction until the tip end portion of the bit shaft portion, the bit shaft portion (2) is provided at its tip end portion with a dust attraction auxiliary passage (6) which extends from the dust attraction passage (4) to be perpendicular or substantially perpendicular to the dust attraction passage (4) and opens so that an outer diameter end (6t) faces a peripheral surface (1F) of the bit shaft portion (2), and a base end portion (3b) of the bit tip portion (3) is integrally attached to the tip end face of the bit shaft portion (2).</p> |
