Abstract: The invention provides an apparatus capable of effecting relative movement between the oval-like girth or circumference of a workpiece and tool means while maintaining the planar and radial workpiece surfaces in a fixed plane relative to the tool means as they are exposed thereto. The apparatus is especially useful in laser welding an oval-like girth joint around a workpiece since the workpiece surface is always maintained in a substantially fixed plane relative to the lens which focuses the laser beam, thereby maintaining proper beam focusing and angle of beam incidence on the surface throughout the entire welding process. For laser welding, the apparatus includes a base in a fixed plane relative to the focusing lens, means for effecting relative translational movement between the base and lens, and bearing and shaft means, including chuck means, for holding the workpiece in proper relation to the lens and for rotating the workpiece about longitudinal axes through the radii of the oval-like workpiece girth.