What is meant by pilgering?

Answer 1

Pilgering is a metal-working process for reducing the dimensions of a metal tube. The two key components of a pilgering press (or mill) are a conical mandrel, which fits inside the tube, and ring dies which roll over the outside of the tube. This process reduces the diameter of the tube to the size of the mandrel and, at the same time, reduces the wall thickness of the tube from the action of the dies rolling over the outside of the tube along the mandrel. Pilgering is usually performed cold, i.e., the metal does not need to be heat-treated for the process to be accomplished, and it takes a very great number of tiny forming steps. This makes it highly suitable to use on precious metals, since almost no metal is lost in the process. This also is a superior metal-forming process to drawing, since it can reduce the diameter of a tube to a greater degree than drawing while the tube still remains round and retains greater tensile strength against forces such as torque and stress fracturing. Cold pilgered tubes are used for such things as lightning rods, Baseball bats and Golf clubs, which can survive repeated sudden large-force impacts.