Abstract: Disclosed is a new and improved method and apparatus for automatically lapping a ball and a seat of a valve to produce a non-flat lapped sealing surface finish that provides a reliable fluid seal at minimum cost. Either the seat or ball is rotated as the work piece by the apparatus while in contact with the surface of a lap member which may be the mating seal part. The lap member is held or maintained in a desired angular or tilt relationship with the work piece. A controllable force spring is provided to maintain the desired lapping force between the work piece and lap member. While the lap member is blocked from rotation about the tilt angle and apparatus swings or oscillates the lap member about the work piece to maximize the effectiveness of the lapping contact.