Method and apparatus for the thread-stitching

A method for thread-stitching for which individual, folded signatures, which are positioned upright and lined up successively along their flat sides, are sewn together with at least one sewing needle, and at least one hook needle to form a book block, the method comprising the steps of:

• moving with the at least one sewing needle a binding thread from an outside to an inside through a fold of a signature to be sewn, between legs of the signature, thereby creating a first, single-strand seam on an outside of the fold;
• storing the binding thread between the legs of the folded signature and, starting from the sewing needle, transporting the binding thread as a binding thread loop far enough in a direction of a movement path for the at least one hook needle, so that a closed end of the binding thread loop extends past the movement path of the at least one hook needle;
• moving the at least one hook needle through an eyelet of the binding thread, created on the outside of the fold during a sewing of a previous signature, and through the fold of the signature to be sewn toward the inside, between the legs of the signature, dipping the at least one hook needle into the previously formed binding thread loop, gripping the previously formed binding loop during a return stroke of the at least one hook needle, moving the previously formed binding loop from the inside through the fold of the signature to be sewn and through the eyelet on the outside of the fold to the outside, thereby creating on the outside of the fold a second, double-strand seam that is spaced-apart from the first, single-strand seam;
• providing the at least one hook needle on one side with a recess forming a hook for accommodating the binding thread used to sew the signature, rotating the at least one hook needle around its longitudinal axis to position the hook at different rotational positions, and prior to penetrating from the inside to the outside of the fold of the signature to be sewn and the eyelet of the previously sewn signature, rotating the at least one hook needle in such a way around its longitudinal axis that its hook is positioned in a vertical plane of symmetry for the eyelet and is positioned on a side of the hook needle that is facing the previously sewn signature.