A machining device has a base and a fixture. The base is fixedly attached to a pallet or a machining table. The fixture is mounted on the base, contacting the base only at projecting contact surfaces which project above the mounting surface of the base. Cleaning of the base before a fixture is attached is done efficiently because only the minimized projecting contact surfaces area between the base and the fixture needs to be cleaned to permit stable contact between the base and fixture. The base and fixture also include projections and holes for precisely aligning the base and fixture with respect to each other.