Hole Expansion

(in Russian, raskatka), an operation during forging that increases the external and internal diameters of a ring-shaped pierced billet with an insignificant increase in length as a result of reduced wall thickness. The operation is performed with a press or hammer. The billet is heated to forging temperature and placed on a mandrel mounted on two supports; the mandrel serves as a base or bottom die, and the top die is narrow and long. The billet is forged between the two dies and is rotated after each compression. The operation is used for making relatively large-diameter ring-shaped parts.