An end-effector that loads disks into a pallet of a sputtering machine, for example, has a two-piece mandrel with a rigid inner core and a plastic outer sleeve slideably axially mounted on the core. The sleeve is attached to the core with a coupling providing a predetermined attachment force. A breakaway force exerted on the sleeve that exceeds the attachment force causes the sleeve to separate from the mandrel, this separation being sensed by a breakaway sensor.