Patent ID: 8365573

Claim:
A mandrel used in a method of manufacturing a hollow rack bar by overhanging a wall of a hollow material from an inner diameter side toward a mold by pressing the mandrel into an inner cavity of the hollow material held to the mold, the mandrel comprising: a bar having a maximum cross section region smaller than a minimum cross section region of a hollow portion of the hollow material; and three projected portions mounted only on a same surface along an axial direction of the bar and including a maximum projected portion with maximum projected extent, each projected portion having smoothly-tapered guide surfaces, wherein the extent of the projected portion positioned at a leading end side in the axial direction of the bar is smaller than the extent of the maximum projected portion, wherein the extent of the projected portion positioned at a base end side in the axial direction of the bar is smaller than the extent of the maximum projected portion, and wherein the maximum projected portion is positioned between the leading end side projected portion and the base end side projected portion.