A machine (28) for use in removing first and second mandrels (20) from a stringer assembly (26) that includes a composite I-beam and the mandrels is disclosed. The mandrels are located in channels on opposite sides of the composite I-beam. The machine includes a framework (30) having an elongate platform (36) for supporting the stringer assembly (26). Mounted on the framework are a plurality of stations (32) located long the longitudinal platform (36). Each station includes first and second movable platforms (42) mounted to opposite sides of the longitudinal platform from one another. Each platform includes a clamp (38 and 40) for sequentially clamping the stringer assembly to the framework when the mandrels are being removed. The movable platforms are attached to the mandrels. A jackscrew mechanism moves the movable platforms with respect to one another when the sides of the stringer assembly are clamped to the platform. The force created by the jackscrews pulls the mandrels away from the composite I-beam, first from one side of the stringer assembly then from the other side. A third clamp (76), mounted to one side of the framework, is used to clamp the one side of the composite I-beam to the framework after the mandrel has been removed from that side of the beam.