Abstract: Coupling shaft for transmitting a torque from the power take-off shaft of a tractor to the input shaft of a driven agricultural machine, which shaft is provided with at least one universal joint, wherein the shaft is protected by a tube of fitting material which is mounted on the shaft by a bearing ring which protrudes into a groove of the shaft and is connected to a cover which is fixed to the tube and which projects over the universal joint, wherein the bearing ring is provided with at least two cam-like protrusions arranged along the periphery of the ring at a mutual distance and the cover is provided with at least two spaces in each case for receiving these protrusions, wherein by an angular displacement of the bearing ring relative to the cover a locking in axial sense is effected between cover and bearing ring, and wherein an insert piece is active between cover and bearing ring to counter an opposite rotation of this bearing ring such that assembly can take place without tools, but disassembly takes pl