Patent ID: 8905158

Claim:
An underreamer tool for use in a wellbore the tool comprising: a body having a longitudinal axis, a tool element and an actuation device configured to urge the tool element relative to the body from a first configuration into a second configuration, wherein a portion of the tool has a curved actuation surface and wherein the tool element is urged across the curved actuation surface of the tool whereby movement of the tool element across the curved actuation surface moves the tool element radially with respect to the body of the tool; wherein the actuation device is hydraulically responsive or pressure responsive; wherein the curved actuation surface comprises an arcuate track and the tool element is mounted on the track so as to permit axial translation and radial movement of the tool with respect to the longitudinal axis of the body; and wherein the track is coupled to the body by a securing mechanism comprising a key provided on one of the track and the body and a slot provided on the other of the track and the body, wherein the slot is larger than the key to thereby provide a gap into which a locking block can be inserted to selectively lock the securing mechanism.