Abstract: An arrangement for mounting a hub on a shaft such as the rotatable head support of a helical scan tape recorder. The hub has a tubular portion coaxial with the shaft, which is clamped onto the shaft by a device having three clamping jaws which are force-coupled to each other and engage the tubular portion at equally spaced locations circumferentially around the shaft in a plane substantially perpendicular to the shaft, the clamping surface of at least one clamping jaw being adjustable by an adjusting device to move the clamping surface in a direction substantially perpendicular to the shaft axis. One or all of the jaws may be pivotally interconnected to the other jaws.