This hub mounts the cutterbar drive assembly to the header frame. It transmits torque from the drive shaft to the knife-drive mechanism through a splined interface. Wear on the internal splines or the bearing seat causes drive-line vibration and uneven knife stroke. The original hub is machined to match the shaft clearance and bearing preload specified for the drive housing. On reinstall, ensure the retaining nut is torqued to specification and that the locking mechanism is engaged.