A scrap processor includes a rotor supported within a chamber in a housing for rotation relative to the housing. Hammer means on the rotor comminute scrap material in the chamber. A deflector box having first and second deflector portions is connected to the housing. The first deflector portion is a mirror image of the second deflector portion. The housing includes a plurality of castings defining the chamber in which the rotor comminutes the scrap material. The castings extend transverse to the direction of flow of scrap material into the chamber and entirely across the chamber. The castings are identical in size and shape and are interchangeable. The housing is constructed with a first plate means having a slot therein and a second plate means having a projection thereon located in the slot to transfer forces acting on the first plate means to the second plate means.