This nut secures the pivot bolt in the threshing mechanism of a self-propelled forage harvester. It is installed on the bolt that connects the flail or beater assembly to the rotor; the nut maintains the correct clamping force so the bolt does not loosen under the high vibration and impact loads of the cutting process. A loose nut allows the bolt to shift, which can cause the flail to strike the housing or shear the bolt. This is an original-manufacturer component, so its thread pitch and seating face match the bolt and the counterbore in the rotor arm without the need for a washer or shim. On reinstallation, clean the threads and torque the nut to the specification for the host machine.