PIERCING APPARATUS, PLUG USED FOR PIERCING APPARATUS, AND METHOD FOR PRODUCING SEAMLESS STEEL PIPE

摘要

Provided is a boring device wherein the occurrence of flaws in the inner surface of a hollow shell is suppressed. A boring machine (10) according to an embodiment of the present invention is a boring device (10) for boring a billet (18). The boring device (10) comprises a plug (14). The plug (14) has a through-hole (30). The through-hole (30) extends along a central axis, and a central part of the billet (18) to be bored is passed therethrough.