Abstract: A disk refiner for producing paper pulp has two counter-rotating rotors to which are mounted refining disks which spin with respect to one another to refine a stream of suspended pulp. Each disk has an outer disk ring with a plurality of radially extending refiner bars. The outer disk ring is substantially annular. A fastener extends into a threaded mounting hole in the outer disk ring to connect it to a rotor support. An inner disk ring has a plurality of protruding refiner bars which extend radially toward the outer ring. A mounting tab extends from the inner disk ring refiner bars beneath the outer disk ring. Fasteners extend through mounting holes in the mounting tab to connect the inner disk ring to the support. The fastener is covered by the outer disk ring and substantially protected from erosion thereby.