| 摘要 |
<p>A drill bit (1) includes a mount (2) to be mounted on a power tool; and a body portion (4A) having a hollow cylindrical shape with center axis (X), a cylindrical surface, a base end, and a tip end (4B). The body portion being connected with the mount at the base end to rotate coaxially with the mount portion and cut a workpiece. A flat tip-end portion is provided at the tip end extending in a direction perpendicular to the axial direction. An outer circumferential portion (42) is provided adjacent to the tip end of the body portion; and a connecting face portion (43) is provided between the outer circumferential portion and the tip-end portion, all of which are covered with abrasive grains to form an abrasive grain layer (5A). The connecting face may taper towards the tip-end portion. The thickness of abrasive grain layer on the connecting face may be thicker than the layer on the tip-end portion.</p> |
