If you want to make a pipe out of sheet metal and you want to close the rounded material with a seam, there are two options. First, you use the Pittsburgh lock former machine and 3-roller bending machine a seam on both ends of the blank. After the first run, you flip the workpiece so that the two seams face in different directions. Then you round the sheet on a 3-roller bending machine and hang the two folds in each other.