Drawing of metal tube of tapering wall thickness - uses conical drawing plate insert which is advanced as tube is drawn to produce tennis racket shaft

摘要

The process for drawing metal tube of tapering wall thickness (13b) uses a tapered or stepped drawing plate insert (6), with the relative axial disposition of the drawing plate (4) and insert (6) subject to controlled adjustment. The method may be applied to the prodn of tubular metal tennis racket shafts, and obviates electrolytic tapering. The drawing plate (4) and the insert (6) are mounted on a drawing bed with a traction carriage pulling the leading end of the tube (5), the insert anchored to the bed beyond the trailing rube end, and the drawing plate in an intermediary position. The insert may comprise a rod (7) which fits inside the tube (5) and has a part-conical or step diametered nose. The drawing plate (4) may be mounted in a cage holder (3) on a slide. The slide and thus the drawing plate may be displaced axially by a jack operated lever cam. Micrometers may be deployed to monitor resultant wall thickness, and the variation in wall thickness is effected by progressively advancing the insert (6) as the tube (5) is drawn.