| 摘要 |
A reaming tool for enlarging an underground borehole has a plurality of cutter assemblies distributed azimuthally around a longitudinal axis of the tool, wherein each cutter assembly includes a supporting structure bearing a sequence of cutters 308 which extends axially along the tool with leading surfaces facing in a direction of rotation of the tool. The cutters 308 of each sequence are positioned at a plurality of circumferential positions such that a plurality of cutters 308 in the sequence have a leading face circumferentially behind the leading face but ahead of the trailing end of at least one other cutter. |
