Apparatus and method of forming an annular member

A method of forming an annular member comprising the steps of:

• providing a rotatable forming roll in contact with an outer cylindrical surface of an annular workpiece;
• providing a mandrel movable relatively towards and away from the forming roll and confronting the forming roll in contact with an inner cylindrical surface of the annular workpiece;
• providing outside diameter detecting device for detecting an outside diameter of the annular workpiece which is to be worked;
• relatively moving the forming roll and the mandrel in a closing direction to sandwich the annular workpiece between the forming roll and the mandrel to subject the annular workpiece to rough rolling and to finishing rolling;
• and
• controlling the relative movement of the forming roll and the mandrel so that the moving device relatively moves the forming roll and the mandrel in a separating direction opposite to the closing direction by a predetermined distance during the change from the rough rolling to the finishing rolling, and
• wherein said predetermined distance is substantially equal to a difference between an elastic deformation of the annular member forming apparatus occurring in the rough rolling and an elastic deformation of the annular member forming apparatus occurring in the finishing rolling.