Downhole adjustable bent assemblies

In accordance with an illustrative embodiment of the present invention, a downhole adjustable apparatus for creating a bend angle in a drill string includes a mandrel mounted for rotation between first and second angular positions within a housing, the mandrel being telescoped into the housing on an axis that is inclined with respect to the principle axial centerline of the housing, so that in one rotational position of the mandrel the housing is axially aligned with the centerline of a drilling motor and in another rotational position that is 180 DEG from the initial position the housing is slightly inclined with respect to the centerline of such drilling motor to establish a bend angle. Further manipulation of the mandrel is used to return the members to their original positions for straight-ahead drilling.