PURPOSE: To easily finish the outer surface of a bar-shaped body into the prescribed shape, by loosely fitting the bar-shaped body into a forming cylinder having an expansion coefficient smaller than that of the bar-shaped body, and cooling them to extract the body after heating the body to tightly press the outer surface of the body to the inner surface of the cylinder.

CONSTITUTION: A cylindrical bar-shaped body 1 made of aluminum, etc., of which outer surface is previously machined, is loosely fitted into a forming cylinder 2 having the prescribed dimensions and shape of its inner surface. The cylinder 2 has the inner diameter slightly larger than the outer diameter of the body 1, and is made of a material such as iron or ceramics having an expansion coefficient smaller than that of the body 1; the hardness of the inner surface of the cylinder 2 is made considerably larger than that of the outer surface of the body 1, and said inner surface is finished in the prescribed accuracy. Next, the body 1, or the body 1 and the cylinder 2, is heated to tightly press the outer surface of the body 1 to the inner surface of the cylinder 2, and then, only the body 1, or both of them, is cooled to produce a gap between the body 1 and the cylinder 2 thereby extracting the body 1 from the cylinder 2.