A cylindrical shaft 1 is machined at room temperature to be of substantially perfect circular shape in cross section. It is then subjected to an elevated temperature which is the same as that to which it will be subjected in use and circumferential distortions (11) of the shaft relative to a perfect circular shape at longitudinally spaced positions (X₁, X₂...X n ) are measured. Degrees of correction are determined based on the measured distortions and the article is then machined again at substantially room temperature in accordance with the degrees of correction to impart a non-circular shape to the article. When the article is used its cross sectional shape is then substantially perfectly circular.