Abstract: A comminuting machine rotor assembly comprising rotors carried by a shaft for conjoint rotation with the shaft, hammer heads carried by the rotors and extending radially outwardly from the shaft, and hammer inserts releasably attached to respective ones of the hammer heads. There is a wear material coating over at least a first cutting edge of an insert body of each insert. The first cutting edge of each insert body is defined by a front facet generally facing the direction of assembly rotation, a radially outer end facet adjacent the front facet, and an intervening radially distal corner of the hammer insert formed at the intersection of the front and end facets. The front and end facets are disposed at a relative angle of greater than 60 degrees to one another.