This washer sits between bolted components in the header assembly of a self-propelled forage harvester or combine. It distributes clamping load evenly across the joint face, preventing localized deformation of the mating parts. A missing or undersized washer can allow the fastener to loosen under vibration, leading to misalignment of the header drive components. The washer is manufactured to the original thickness and concentricity specification so that it seats fully in the recess without shifting during torque application. On reinstall, ensure the washer is not reused if it shows any edge deformation or crushing.