Abstract: An apparatus for securing an end cap including an end cap flange to a shell including a shell flange by forming a lip portion including the end cap flange and the shell flange into a lock seam portion in which the end cap flange and the shell flange are engaged with each other. The apparatus includes an elongate tool element rotatable about the central axis, for receiving the end cap thereon. The apparatus also includes a number of roller subassemblies for forming the lip portion into the lock seam portion. Each roller subassembly includes a forming roller engageable with the lip portion while the tool element rotates. Each roller subassembly also includes an arm on which the forming roller thereof is rotatably mounted, and a support mechanism for positioning the arm to engage the forming roller with the lip portion.