This washer sits at the interface between the threshing drum shaft and its bearing housing. It provides a precision spacer that maintains the correct axial clearance between the rotating drum and the stationary frame. A worn or missing washer allows the drum to shift, causing contact between the drum rasp bars and the concave, which produces metal-on-metal noise and reduces threshing efficiency. The integrated nose on this washer aligns with a corresponding notch in the housing, preventing rotation during operation. On reassembly, ensure the nose engages fully with the locating slot and that the retaining hardware is torqued to specification.