| 摘要 |
<p>The present invention provides a drilling tool (1) including: an inner device (4) inserted within a casing pipe (2) in such a way as to be extendable and retractable along the centerline thereof; and a drill bit (5) attached to the distal end part of the casing pipe (2), the drill bit (5) being capable of engaging the inner device (4). The drill bit (5) has a first section (10) provided with at least one drilling member. The drill bit (5) has a wall surface (20c) against which the distal end part of the inner device (4) is capable of abutment in the centerline direction. The maximum outside diameter of a first section (19) of the drill bit (5) is greater than the outside diameter of the casing pipe (2).</p> |
