A sealing apparatus is provided for a pivot assembly on a disc mower incorporating a disc cutterbar to sever standing crop material by impact action. A first circular labyrinth seal has a T-shaped cross-section and fills a correspondingly-shaped groove between the pivot support arm and the gearbox housing. The combination of the T-shaped groove and corresponding labyrinth seal creates a labyrinth path for the entrance of dirt into the pivot assembly. A second circular face seal is constructed with a deformed inner diameter to create a lip that engages the face of the gearbox hubs. The deformed inner diameter lip of the face seal creates an inner cavity underneath the seal that can be filled with grease to provide a further deterrent to the entry of dirt into the pivot mechanism.