Does anyone know of a facing reamer that could be used to restore the sealing surfaces in the cases? I was thinking of making something our of a spot facing cutter with a pilot that would screw into the M22x1.5 drain/fill plug holes. It would serve to center and square the cutter and also prevent chips from entering the gear cases. It would be hand driven to prevent too much material from being removed. My only impediment is not having access to a lathe.

How have you adapted to damaged seal washer surfaces?