Improved apparatus is provided for spreading the seam edges of formed large diameter pipe so that it can be mounted more quickly onto the arbor of a welder. The conventional spreader apparatus comprised of a fixed straight arm with rollers on opposite ends has at least one cylinder axially substituted for at least part of its length so that the rollers are retractable. The cylinder is mounted in a bracket and freely slidable back and forth axially so as to be self-centering thus preventing displacement of the seam from proper alignment with the arbor as it is spread preparatory to movement thereon. Preferably, a pair of cylinders are provided attached in back to back relation with a roller connected to each piston rod thereof.