What is Pilguring of Tubes?

Cold pilgering is a longitudinal cold-rolling process that reduces the diameter and wall thickness of metal tube in one process step. Depending on the material, the cold pilger process achieves cross-section reductions of more than 90 percent in a single working cycle.
Fig 1
The cold pilgering process relies on four main actions: The tube moves forward and it rotates while the ring dies move back and forth and rotate.

The process can achieve variations smaller than 0.5 microinch for medium ODs and wall thicknesses. The roughness value of the finished tube usually is less than that of a drawn tube. With stainless steel tubes, for example, cold pilgering can achieve Ra values smaller than 0.02 microinch. 

Typical materials are mild steel, stainless steel, ferritic steel, low-alloy steel, copper and copper alloys, titanium alloys, zirconium alloys, and nickel alloys . Using cold pilgering to reduce precious metals is conceivable, because practically no material loss occurs. The deformation strengths of the cold pilgered tubes range from 400 N/mm² for copper to more than 1,500 N/mm² for special alloys. 
 Courtesy
http://www.thefabricator.com/article/tubepipeproduction/introducing-cold-pilger-mill-technology