Abstract: An annular bearing has its bearing surface on the inner surface. The bearing surface is formed to improve bearing properties, that is, to improve adaptability to an impact load and an imbalanced load. A method of manufacturing a bearing having such a bearing surface is given. An annular bearing blank, together with a mandrel having a plurality of arch-shaped ridges extending axially on the outer surface of the mandrel and a sleeve fitted on a periphery of the mandrel, is pushed into an inner hole of a molding die. The material is accordingly closed in a space defined by the mandrel, the inner hole, the sleeve and an ejector inserted into the bottom part of the inner hole. Thus, a plurality of arch-shaped recesses are formed extending axially on the inner surface of the bearing blank.

Abstract: A bushing having an outer sliding surface is produced by a die forming method without machining. A crowning shape is provided to the outer surface so that the outer diameter of the bushing is smaller at its opposite longitudinal ends, and increases progressively toward a central zone of the bushing. A cylindrical bushing blank is fitted on distal end portion of a vertically-movable mandrel. Next, one of an upper die and a lower die is reactively moved toward the other to plastically work the bushing blank by the both dies and the mandrel, thereby working the bushing. An inner diameter of the upper die is larger at its lower end, and decreases progressively away from the lower end, and an inner diameter of the lower die is larger at its upper end, and decreases progressively away from the upper end.

Abstract: 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.