PLASTIC WORKING METHOD AND SPINNING MACHINE USING SAME

摘要

To provide a spinning machine that can assure precision in products requiring high precision in shape dimensions on the outside surface side even if there is variation in length dimensions and sheet thickness dimensions of material with a cylindrical shape having a bottom, a spinning machine (1) is provided with: a main shaft (3) on which is deployed a regulating member (11) that runs into a chuck (4) that sandwiches a peripheral surface of material (W) with a cylindrical shape having a bottom and into the outside bottom surface of the material (W); a mandrel (5), which is inserted into the inside of the material (W) from an opening side end part thereof, the tip thereof running into the inside bottom surface of the material (W), sandwiching the bottom of the material (W) with the regulating member (11); and a pressing roller (6) that applies pressure on the opening side end part of the material (W). By pushing the pressing roller (6) in a direction approaching the mandrel (5) while the material (W) is being rotated about the axial center of the main shaft (3) when the main shaft is rotatably driven, a groove part with a cylindrical shape is formed in the opening side end part of the material (W) such that the inside diameter of the opening side end part is smaller than the inside diameter of a shank part of the material (W). At least the part of the mandrel (5) that is inserted inside the material (W) is formed such that a space (S) is provided between that part and the inside peripheral surface of the opening side end part of the material (W) after plastic deformation of the same.