Abstract: The present invention provides seam-welded, air hardenable steel tubes, methods of manufacturing seam-welded air hardenable steel tubes, tube mills for practicing such methods and applications for using seam-welded, air hardenable steel tubing of the present invention.

Abstract: The present invention provides skinned structures of air or liquid quench hardenable steel plates or sheets, and methods of constructing such structures. The present invention also provides hardened skinned structures made from a plurality of air or liquid quench hardenable steel plates or sheets that are made by such methods.

Abstract: A racquet stringing machine which accomplishes tensioning of the strings of a racquet by the use of one or more combination tensioning and holding clamp units which operate directly on the string inside the racquet. The present invention also provides fixed, non-rotating racquet head frame holding fixture holds the racquet stationary throughout the stringing process. The racquet is supported against distortion by compressive mounts disposed along the outer perimeter of the racquet head frame only. The racquet stringing machine further includes an offset pedestal which stabilizes the machine by counterweight effect while keeping the floor beneath the racquet holding fixture free of obstruction.