Abstract: An underreaming tool with cutter arm position indication. An elongated body portion has a coupling for coupling one end thereof to a lower end of a lower drill string. A pair of arms are pivotally mounted on the body portion. Means is provided for relatively positioning the cutter arms apart in a cutting position and closer together in a non-cutting position and having an overridable condition wherein either of the cutter arms may be either in a cutting or a non-cutting position. A fluid passage is provided in the body portion comprising an input port at one end of the body portion and first and second output ports. One output port is adjacent to each of the cutter arms.

Abstract: 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.