Method for forming seams in box-shaped members

摘要

A method and apparatus for forming the locking bend on a Pittsburgh type seam used in joining the sections during assembly of box-shaped sheet metal ducts. The apparatus provides a means for securely holding the duct without the use of a mandrel to permit the sheet metal along the seam to be bent over by a forming roller moving along the seam so as to complete the joint and lock the seam.