Abstract: An apparatus for holding a workpiece to a known position without regard to the angularity of the surface of the workpiece at the point of contact with the apparatus includes a disk shaped, substantially flat contact pad for engaging the workpiece. The surface of the contact pad opposite the workpiece is substantially spherical and fits in a conical seat so that the center point of the upper surface of the contact pad is always at an known position when the contact pad is seated, without regard to the angularity of the contact pad. A proximity detector determines when the contact pad is seated providing an indication to an operator that the workpiece is properly engaged by the apparatus. The contact pad is contained within the interior of a suction cup that engages the workpiece whereupon externally supplied vacuum pulls the suction cup and the workpiece together.