hollow-forge

[hol-oh-fawrj, -fohrj]

verb (used with object), hol·low-forged, hol·low-forg·ing.

to produce (a tube or vessel) by trepanning a hole in a forging and expanding it with further forging on a mandrel.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019