This bushing fits onto the shaft of the threshing drum, providing a wear surface between the rotating drum and the stationary frame. It maintains the radial alignment of the drum within the threshing housing, preventing metal-to-metal contact that would accelerate shaft and housing damage. As the bushing wears, clearance increases, allowing the drum to shift out of alignment, which can cause uneven threshing clearance and increased vibration. The bushing is machined to the original inner and outer diameter tolerances, so it seats into the housing bore without additional shimming. On installation, ensure the bore is clean and free of debris before pressing the bushing into place.