Patent ID: 8047193

Claim:
A non-core drill bit comprising: a metallic seat attached to a tip of a shank of a boring tool; a first diamond grindstone body, having an approximately annular or cylindrical shape, fixed to the metallic seat, and having a recessed cutout portion opened to an outer periphery face; and a second diamond grindstone body installed inside the recessed cutout portion; wherein a tip of the second diamond grindstone body in an axial direction is positioned on a side of the metallic seal from a lip of the first diamond grindstone body in the axial direction, wherein an inner side of a tip face of the first diamond grindstone body is formed in a reverse-conical recessed shape, and transforms into a planar outer peripheral edge, the planar outer peripheral edge adapted to engage a material to be bored before the inner side of the tip face.