Abstract: A rocker mill for reducing the diameter of metal tubes includes a rollstand mounted on a reciprocable sled. The rollstand includes upper and lower roll dies between which the tubes travel as the sled and rollstand are reciprocated. The roll dies are mounted on tapered segments of respective arbors to facilitate removal of the roll dies. The arbors are driven by respective spur gears which are in meshing relationship on one side of the rollstand. One of the spur gears is driven by a pinion gear coaxially attached thereto on the same side of the rollstand as the spur gears. The rollstand is arranged to be slid horizontally from the sled after a plurality of fasteners have been released. A stationary toothed rack which drives the drive gear is spring-biased vertically to raise the rack in order to facilitate the sliding of the rollstand off the sled.