A coupling, arranged to form a frictional joint between two mechanical elements, comprising a tubular contact member, arranged to take up a non-deformative frictional contact with an element to be attached by means of a first peripherical surface when force transforming ring having a conical contact surface is moved against a co-acting conical contact surface at the opposed peripherical surface of the contact member by means of a manually operated and linearly movable force applying member, thereby applying a force at one point along said surface of the contact member, said contact member being arranged with such a longitudinal section that the force applied at one point by the force transforming ring is equally distributed along the surface in contact with the member to be attached.
