DIRECTIONAL DRILLING SYSTEM
A drilling assembly comprises an outer housing, a drive shaft, an articulated steering shaft assembly, a drill bit at end of steering shaft assembly and an eccentric fulcrum support though which the steering shaft assembly passes. The fulcrum support centre being offset from the centre axis of the drill string and is able to be rotated about drill string axis to change the direction of the drill bit. A key and keyway being disposed between the eccentric fulcrum support and the outer housing, so that the joint can be rotationally positioned by axial movement along the drill string axis.