Piercing a seamless steel tube is a forging operation in which the metal is worked from the inside as well as the outside. The substantial amount of metal displacement, as the tube is pierced while spinning at high rpm, results in a refined grain structure and uniform grain flow. At the same time, the steel fibers are given a slight spiral twist, which results in greater strength and ductility.

The tube making process includes four hot working operations:

1. The piercing of the billet, which produces a tube hollow at approximately one foot (.3 metre) per second.
2. Elongating or plug mill rolling to establish the tube wall.
3. Rolling or sinking the tube to establish the approximate outer diameter.
4. Rounding and sizing the tube outer diameter to decimal dimensions.

These operations are monitored to produce a tube with uniform properties from the surface through the wall and from one end to the other.