This hex nut secures the blade assembly on the chopper drum of a forage harvester. It is installed on the mounting stud that holds the cutting knife in position against the drum. A loose or missing nut allows the blade to shift, causing uneven cut length and potential damage to the counter-knife. This original-manufacturer nut is formed to the same thread class and hardness as the factory component, so it maintains the correct clamping force without deforming under the high-vibration environment of the chopper. When replacing, clean the stud threads and tighten the nut to the torque specification for the assembly.