Abstract: A collet-clamp for retaining label supply rolls on a dispensing shaft. The collet has a plurality of fingers that can be tightened against the shaft when the clamp is moved axially toward the collet. The base of the collet supports a plurality of helical wedging surfaces that cooperate with annular segments formed on the axial hub of the clamp in order to cause the clamp to be brought closer to the collet when the clamp is twisted in a predetermined clamping direction with respect to the collet. The collet and clamp are assembled by bringing the annular segments of the clamp into cooperative engagement with the helical wedging surfaces of the collet by twisting the clamp with respect to the collet in the direction opposite the clamping direction prior to placing the collet-clamp fitting onto the shaft. While on the shaft the collet-clamp fitting cannot be disassembled.