Adjustable length drilling sub

摘要

An adjustable length drilling sub is disclosed for placing in a drill string between stabilizers to allow the distance between the stabilizers to be changed while the drill string is in the well bore to adjust the rate the angle of the well bore from the vertical is changing. The sub includes an outer member and an inner member that extends into the outer member with an annular space between the members. Protrusions in the form of drive pins mounted in the wall of the outer member extend into the annular space to move into and out of engagement with cavities formed on the outer surface of the inner member. When the pins are in engagement with the cavities, torque in one direction and weight can be transmitted to the bit. When the pins are rotated in the other direction out of the cavities, the members can be moved longitudinally relative to each other to change the distance between the stabilizers.