Subclass 1/095: Couplings for rigidly connecting two coaxial shafts or other movable machine elements (for attachment of cranks to their shafts F16C 3/1 ) for attachment of a member on a shaft or on a shaft-end (attachment of marine propellers on shafts B63H 23/34) with clamping hub; with hub and longitudinal key with radial clamping due to axial loading of at least one pair of conical surfaces using one or more elastic or segmented conical rings forming at least one of the conical surfaces, the rings being expanded or contracted to effect clamping (F16D 1/091 takes precedence) with clamping effected by ring contraction only