| 摘要 |
A drill attachment comprising a twist drill bit 1 with a shank, intended for attachment to any suitable tool, and a grindstone 2 attached to the shank of the twist drill bit 1. The grindstone 2 is bonded to the shank, and supported by a shoulder 3 on the shank. The grindstone 2 may be cylindrical with two planer surfaces with a longitudinal hole between them. |
