Abstract: A barrel and a cover, to be combined into a container, are rotated by a preliminary machining feeder while they are supported by a first rotatable seaming chuck and a first holder. During rotation of the preliminary machining feeder, a flange of the barrel and an end hook of the cover are pressed by a first seaming segment against the first seaming chuck, so that the barrel and the cover are preliminarily fastened and necked in. The barrel and the cover are then transferred by a transfer unit to a final machining feeder on which the barrel and the cover are supported by a second rotatable seaming chuck and a second holder. The final machining feeder is rotated to feed the barrel and the cover while they are finally fastened and necked in by a second seaming segment. The first and second seaming segments are arcuate in shape and have their inner shaping surfaces progressively approaching the preliminary and final machining feeders, respectively, in the direction of rotation thereof.