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Precision machinery needs precision-manufactured parts. When a machine requires metal tubing, the tube may not need to be the same diameter throughout the entire length. Using a metal forging process called tube swaging, a tube can be custom designed so that its diameter is altered to meet the specific requirements of a machine. The word swage may apply to either the swaging process or to the tools used to complete the swaging.
Tube swaging is a type of metal forging that uses dies to create the specific shape. The term die generally refers to a custom-made form that cuts or alters the shape of a piece of metal. In the case of tube swaging, dies can be used to increase or decrease the diameter of the tube. To increase the diameter, a die is inserted into the opening of a tube and it is forced to assume the shape of the die. To reduce the diameter of the tube, dies are used as hammers on the outside of the tube in order to condense the material and shrink the overall diameter.
In some cases, tube swaging can include both internal and external swaging. In other words, a tube may need to be one shape on the inside and another shape on the outside. For example, certain tubes need to fit over and lock onto another distinctly shaped part, but are still required to have a typical tubular shape on the outside. Swaging can be used to change the inside shape of the tube while changing the outside diameter to whatever size might be needed.
Rotary swaging is a common type of tube swaging which uses a cold process to shape, taper or point a metal tube. While the tube is rotated on a spindle, the rotary swage uses a series of dies that repeatedly open and close as often as 2,000 times per minute. There are two types of rotary swages: a standard or tagging machine and a butt swaging machine. The standard machine works by enclosing the entire length of the tube in the dies, while a butt swaging machine closes the dies on the metal tube only when indicated by the operator. This is usually accomplished with a foot pedal and results in a tube that is altered at both ends or at multiple points along the length of the tube.