Seamers Seamers Linear seam welders are generally intended to make single pass, full penetration welds. Most arc welding processes can be used. Parts welded are usually cylinder, flat sheets, cones, or similar type geometries. Butt joints are common, with heavy gauge material normally being tack welded prior to loading into the machines. Copper tipped fingers hold the edges against a copper backing bar to chill the weld zone and prevent burn through. Standard versions are built to Bancroft specifications. Special versions, with varying degrees of automation, are also available. Costs for linear seam welders are available by special quotation.