A pull or push rod for a molding machine having a groove. The groove is suitable for forming a positive-locking connection with a locking nut, by which positive-locking connection forces are transmittable between the locking nut and the pull or push rod. The groove has a groove cross-section, has at least two groove flanks, and has a groove base. The at least two groove flanks, viewed in the groove cross-section, each transition with at least one transition curvature into the groove base. The groove base in the groove cross-section is at least partially formed as a curvature, and the curvature of the groove base differs from the transition curvatures of the groove flanks.