Abstract: A method and apparatus for riveting together workpieces which, in their assembled relationship, have non-parallel exterior surface. Apparatus is provided for clamping the workpieces together between an upper clamp pad and a lower clamp pad, the lower clamp pad being mounted on a spherical bearing so that the lower clamp pad can conform to the workpiece surface. The lower clamp pad is provided with a conical aperture which can act as a pilot for tooling. The tooling is also mounted on spherical bearings so that when the lower clamp pad is in contact with the lower surface of the workpiece, and the tooling is moved towards the workpiece. The tooling will be piloted by the conical aperture to be normal to the surface. After the workpieces are clamped together, the workpieces are drilled from the upper surface and the upper surface is also countersunk.