The invention relates to a mounting device (1) for a center part (4) rotatable about a rotary axis (6) in an injection molding device. The mounting device comprises at least one lower mounting device (2) having a modularly constructed lower cross member (7). The cross member (7) comprises a center block (9) and at least one side block (11) fastened to the center block (9). The center block (9) comprises operative connection means for fastening a lower rotary unit (24) for rotatably mounting the center part (4) about rotary axis (6).