Abstract: The present shaft coupling is intended for releasably linking two or more vices to each other in a torque transmitting manner. The devices may, for example, be turbines each of which has a shaft. Two bearing mounts are provided for one of the shafts, but only one bearing mount is provided for the other shaft at its end remote from the coupling. The coupling between the two shafts is formed by inserting a non-circular end portion of one shaft in a corresponding non-circular aperture in the end of the other shaft. An axially extending bolt firmly clamps the two shafts together in the axial direction. One or both of the shafts may be hollow. The non-circular profiles of the shafts may be splined, or have a polygonal profile, and the polygonal profile may be tapered. A polygonal profile as used herein may be one with only three sides.