| 摘要 |
<p>A borehole reamer (10) is provided with reamer rollers (11, 20) each having projecting studs (12) spaced along its length, the rollers each having a major diameter (D) which tapers to a minor diameter (d, d2) at one of its ends (18) at least, and in some instances the minor diameter (d) exists at both ends.</p> |
