| 摘要 |
A downhole tool (10) comprises a body (14), radially extendable members (16) mounted to the body and movable between retracted and extended positions, a cam member (32) operatively associated with the extendable members and movable relative to the body to extend the extendable members, and a support member (30) configurable to permit retraction of the extendable members (16) from an extended position. The tool may be an under-reamer, and the extendable members may be cutting blades (16).
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