BORING MACHINE, PLUG, AND METHOD OF MANUFACTURING SEAMLESS STEEL TUBE

摘要

A plug (2) used for a boring machine, comprises a tip part (23), a cylindrical part (24), a body part (25), a core joining part (22), and a jetting hole (21). The jetting hole (21) is passed through from the surface of the cylindrical part (24) to the surface of the core joining part (22), and jets a lubricant fed from the outside thereto. A bored material forms a clearance from the cylindrical part (24). Since the jetting hole (21) is formed in the cylindrical part (24), the material during boring is not brought into contact with the jetting hole (21). Accordingly, scores resulting from the contact of the material on the jetting hole (21) can be prevented from occurring on the inner surface of the material.