Abstract: The invention provides an impact member for assembly with a rotor arranged in a comminuter used for the size reduction of feed material. The impact member, disposed radially about the rotor, comprises a carrier and a replaceable impact plate both configured for complementary registration so as to be cantilevered from the carrier and to provide an essentially locking arrangement to withstand the impact forces without coming loose. The carrier has a forwardly disposed open recess or channel with first and second facings intersecting in an axial direction relative to the horizontal axis of the rotor, and defining an acute angle relative to the radial plane of the rotor. The first facing is oriented in the general direction of rotation of the rotor and terminates with a longitudinally extending marginal edge disposed axially relative to the horizontal axis of the rotor.