A pair of substantially identical shuttle tables are mounted on the bed of a vertical spindle machine tool on opposite sides of the worktable thereof. A first pallet is mounted on the worktable and a second pallet is mounted on one of the shuttle tables. Both pallets have a tunnel therein that extends all the way through the pallet. A hydraulic ram with an elongated piston rod is mounted on each shuttle table. Each piston rod is long enough to pass completely through the tunnel in an adjacent pallet and to bear against a pallet on the worktable while the base of the piston rod bears against the adjacent pallet. When the piston rod is extended, both pallets are simultaneously pushed in the same direction so that the pallet on the worktable is shifted to the empty shuttle table while the pallet on the other shuttle table is shifted onto the worktable. When the piston rod is subsequently retracted, both pallets remain in their shifted position. When the other piston rod is extended, both pallets are simultaneously pushed back to their original positions.