Abstract: A mounting device for anchoring a machine element coaxially on a rotary shaft. The device fits between the interior cylindrical bore of the machine element and the internal cylindrical surface of the shaft and is effective to position the element at any desired position longitudinally of the shaft and at any angular position circumferentially of the shaft. The device has inner and outer segmented sleeves, the mating surfaces of which are similarly tapered so that relative axial displacement of the sleeves effects expansion and contraction of the interior bore and external surface of the combined elements. At one end the inner sleeve is externally threaded to cooperate with an internally threaded nut, such that rotation of the nut on the threaded portion of the inner sleeve effects the relative axial displacement of the segmented inner and outer sleeves.