structural:expansion, quality:correction
First operation

Once brought together in the seamer, the seaming head presses a first operation roller against the end curl. The end curl is pressed against the flange curling it in toward the body and under the flange. The flange is also bent downward, and the end and body are now loosely joined. The first operation roller is then retracted. At this point five thicknesses of steel exist in the seam. From the outside in they are: