Abstract: An upstanding hollow rotary drum is provided and is mounted for rotation about its center axis. The lower end of the drum is closed and the upper end of the drum is open. A motor is drivingly connected to the drum for rotating the latter at generally 7000 to 8000 R.P.M. and the interior of the drum includes structure for stationarily mounting one or more crab cores within the drum introduced there into through the open upper end thereof and with the crab cores being supported in generally centered position relative to the axis of rotation of the drum. The drum is of an inside diameter sufficient to enable a plurality of crab cores to be received within the drum in centered position therein and to have the outer peripheral portions of the crab cores spaced only slightly inwardly of the inner wall surfaces of the drum.