Shaft coupling

A coupling comprising relatively inner and outer members having a common axis, the members being provided with intermeshing splines that have one or more pairs of circumferentially confronting first surfaces, each of the members additionally provided with one or more circumferentially confronting second surfaces spaced from the said first surfaces and extending at an angle relative to the first surfaces, an axially facing abutment distinct from both the first and second surfaces provided on a first of the members, the abutment being positioned relative to the second member so that the second member can abut against it, displaceable means for allowing relative radial displacement between the first and second surfaces of at least one of the inner or outer members, and urging means for urging the first member along the common axis relative to the second member, the urging means being operable to move the first member to an initial position where the first and second surfaces are urged into contact with each other and opposing circumferential forces are imposed on the first and second members and being operable to move the first member to a final position where the first member abuts the abutment.