Underreamer having splined torque transmitting connection between telescoping portions for control of cutter position

摘要

An underreamer is disclosed having longitudinally telescoping upper and lower portions connectable respectively to an upper drill string and a lower drill string. A splined connection is provided between the telescoping portions having first and second engaged positions. Both of the engaged positions transmit torque between the telescoping portions. The splined connection provides a different angular and a different longitudinal position for the telescoping portions in each such position. Means is provided for pivotally mounting a cutter arm on one of the telescoping portions. Means is provided on the other telescoping portion for urging the at least one cutter arm relatively outward from the telescoping portions to an extended underreaming position when the splined connection is in its first position. The cutter arm is positioned inwardly to a retracted clearance position when the splined connection is in its second position.