| 摘要 |
<p>An expandable drill bit (10) comprises a body (14) for mounting on a support string and two roller cutters (12, 13) mounted on the body (14). The cutters (12, 13) are movable between a smaller diameter first configuration and a larger diameter second configuration. In one embodiment the bit (10) is adapted to drill with the cutters (12, 13) in both the first and second configurations.</p> |
