An automated system for exchanging components of a continuous seam-welded tube mill to change from production of one tubular product to another. The components to be changed are mounted upon sub-base units adapted to be removably affixed to a fixed mill base. Alternate sets of changeable mill units mounted on duplicate sub-base sections are provided for off line tooling change and setup. Changeover modules are provided alongside and spaced from the mill base. Bridging roll units are extendible to span the space between the mill bases and the changeover modules, and push-pull units are incorporated in the changeover modules to shift the sub-base sections from the mill base to the changeover module and the previously retooled duplicate sub-base sections from the changeover modules into operative position on the mill bases.