Forming Processes 109
4.5 Cold Heading Process Description
Wire form stock material is gripped in a die with usually one end protruding. The material is subsequently formed (effectively upset) by successive blows into the desired shape by a punch or a number of progressive punches. Shaping of the shank can be achieved simultaneously (Figure 4.5(a)).
Materials
• Suitable for all ductile metals: principally carbon steels, aluminium, copper and lead alloys. • Alloy and stainless steels, zinc, magnesium, nickel alloys and precious metals are also processed.
Process Variations
• Usually performed with stock material at ambient temperature (cold), but also with stock material warm or hot. • Solid die: single stroke, double stroke, three blow, two die, progressive bolt makers, cold or hot formers – the choice is determined by the length to diameter ratio of the raw material. • Open die: parts made by this process have wide limits and are too long for solid dies. • Continuous rod or cut lengths of material can be supplied to the dies.