Steel wire extrusion die for mattres springs, 1996.
© Science Museum / Science & Society Picture Library
In order for the springs to retain their required stiffnes, the wire used needs to be very strong This is achieved by pulling the steel wire through dies which make it progresively thinner, stretching the crystals that form the wire into fibres. The proces generates a lot of friction which heats everything up. Soap and water are used as a lubricant to reduce this and keep the parts cool. Made by Bekaert Engineering of Belgium.