Abstract: A sliding block coupling has a coupling head which comprises devices for arranging an ingoing, driving, and an outgoing, driven, torque-transferring member which rotate together with the coupling head, and sliding blocks arranged in a cylindrical recess situated perpendicular to the rotation axis of the coupling head so as to, in cooperation with the coupling head, transfer torque from one of said members to the other. The devices for arranging one of the two torque-transferring members comprises structure arranged in the cylindrical recess in the coupling head, this structure transferring torque between the member in question and the sliding blocks, and being extended in the longitudinal direction of the recess and, at least in the proximity of both of its ends and on opposite sides of the same, being provided with projections or recesses on which or in which the sliding blocks are arranged between that structure and the wall in the cylindrical recess.