To do this, the billet is heated to between 1200 and 1300°C and then positioned between two rolls arranged at an angle to each other and operating in the same direction, thus locking the billet into a kind of gear mechanism. As the billet progresses lengthwise through the rolls in a helical motion, it is pierced by a plug which is supported at the run-out end of the piercing mill by a freely rotating bar. The alternating tension and compression generated by the helical rotating motion loosen the materials microstructure in the core, and this facilitates the internal "drilling” by the plug.

In the pilger rolling stand, a pair of conical-shaped rolls – one arranged above the other – operates in the opposite direction to the material flow. The thick-walled hollow body, with a cylindrical mandrel inside it, is guided towards the pilger rolls. As soon as it is gripped by the tapered portion of the work pass, a small material wave is sheared off the hollow. This wave is forged to the desired wall thickness on the pilger mandrel by the smoothing portion of the work pass, with the hollow body plus mandrel moving backwards in the same direction as the rolls are rotating – i.e. in the opposite direction to the rolling – until they reach the idler pass of the rolls and are released. As the hollow is rotated it is once again pushed forward between the rolls, and a new rolling cycle begins.

The pierce and pilger method for the production of seamless pipe is also referred to as the Mannesmann process after its inventors, the Mannesmann brothers. It is employed for outside diameters from approx. 60 to 660 mm and wall thicknesses from 3 to 125 mm.

Depending on the ratio of wall thickness to diameter and the weight of the starting ingot, pipe lengths of up to 28 m can be manufactured by this technique. To this end, the largest rolled pipes are reheated and then expanded either by pulling through a plug – a process often performed in several passes to gradually increase the outside diameter or by rolling on a becking mill.