Abstract: Waste materials are introduced into an impeller-created vortex of water and reduced to a pulp wherein the impeller is provided with one or more blades constructed and arranged to cooperate with one or more stationary blades on a sieve surrounding the impeller. The impeller blades, stationary blades, and components of the sieve comprise readily removable and changeable components. The shear blades provide edges which periodically mate upon rotation of the impeller to provide a desired shearing action for the waste pulping machine. The shear members may readily and easily be removed when they become worn or damaged. The stationary shear blades are provided with a beveled edge in order to assists the flow of debris. The beveled edge reduces the likelihood of silverware or untensil becoming wedged between the impeller blades and the stationary shear blades.