Abstract: The rotor of a vertical shaft impact rock crusher is balanced by placing steel balls in a hollow ring attached around the top of the rotor. The vanes within the impeller are constructed to form rock shields on the forward or impact side of the vanes. Rocks are fed into the impeller upon a free floating table. The top of the free floating table is protected by a tungsten carbide disc. Therefore the rocks are moved from the table at reduced rotational velocity less than that of the rotor and are struck by the rapidly rotating rock faces of the rock shield. Ports are placed close to the trailing or back side of the vanes. The top, bottom, and trailing lip of the ports are protected by tungsten carbide pins which are adhered within steel pipes by epoxy. The pins are mounted upon a door by welding to the door which covers the ports. The door may be replaced for ease and rapidity in replacing the pins. The pin along the trailing lip of each port is supported by a seat of weld metal.