Abstract: A rotary tub grinder in which a substantially cylindrical tub member is rotated relative to a stationary floor member. Material in the tub grinder is moved over the upper surface of the floor member and a portion of it is moved up a ramp into the path of a rotating hammermill. A stabilizer member is positioned on the floor member across the opening from the ramp member and serves to steady the material so that the hammers of the hammermill can uniformly feed material downwardly into the grinder. The stabilizer member extends higher above the floor member than the ramp member and the path of the rotating hammers extends higher above the floor member than the stabilizer member. A layer of material is planed off as it moves about the tub grinder. The ramp member and stabilizer member also serve to help prevent material from falling into and clogging the grinder when the tub grinder is shut down or slowed down by a power governor.