Abstract: A pneumatically expandable mandrel for winding multiple strips of web material on a plurality of cores spaced axially on the mandrel includes a shaft having a hollow tubular portion. Each core is supported by a separate group of flanged arcuate shells angularly spaced around the periphery of the tubular portion of the shaft, each shell being mounted on a stem that extends through a corresponding opening in the tubular wall and has an enlarged foot that is spring biased against a rubber tube extending through the center of the tubular portion of the shaft. Inflation of the rubber tube expands the shells of each group into contact with a respective core.