Forming method of bushing with inner sliding surface

摘要

An inner sliding surface layer of a bearing bushing is formed into a crowning shape in an axial direction by a die shaping method. A bushing blank fitted on a generally-tapered lower end portion of an upper mandrel is inserted, together with the upper mandrel, into a hole in a forming die, and the bushing blank is deformed between the forming die, the upper mandrel and a lower mandrel having an upper end portion similar in shape to the lower end portion of the upper mandrel, thereby obtaining the bushing having the sliding inner peripheral surface of a crowning shape.