| 摘要 |
<p>This invention relates to a method and a drilling tool for down-the-hole drilling, which drilling tool is intended to drill a hole ahead of a following casing tube (13) having an outer diameter (D), the drilling tool comprising a central pilot drill bit (20) with cutting buttons arranged to form a hole (A) of a first diameter (D1), a reamer (33) and a guide body (12) for steering the drilling tool and casing tube relative to one another, said reamer (33) having a first set of cutting buttons (49) arranged to enlarge said hole (A) to a second diameter (D3), wherein at least one second cutting button (490) is arranged on the reamer (33) in a transversal plane (P1) that is closer to the central pilot drill bit (20) than the transversal plane (P2) of said first set of cutting buttons (49) and at a diameter (D2) that is smaller than the diameter (D2) for said first set of cutting buttons (49), wherein said diameter (D2) of said at least one second cutting button (490) is arranged to create an intermediate edge (B) substantially corresponding to the diameter (D) of said casing tube (13).</p> |
