from the GNU version of the Collaborative International Dictionary of English
- adj. Drawn out from a heated solid bar, as by a process of spiral rolling which first hollows the bar and then expands the cavity by forcing the bar over a pointed mandrel fixed in front of the rolls; -- said of a weldless tube.
from The Century Dictionary and Cyclopedia
- In metal-working, drawn from hollow ingots, in which mandrels of constantly decreasing diameter are successively inserted, till both exterior and interior diameters are brought down to the required dimensions.
Sorry, no etymologies found.