After the leather has been soaked in the lime solution, the leather is scraped to the desired thickness. The leather is then cut into T-shaped pieces of different sizes, in accordance with the orders received by "Oter Israel" and in accordance with the final size of the Tefillin. The sizes of the Tefillin produced by "Oter Israel" range from the largest, that are used by Chabad (Lubavitch) Chasidim, to the very small Tefillin that are one of "Oter Israel`s" specialties.
The production of the four compartments of the head Tefillin from a single piece of leather:
Once the process of tanning has been completed, when the leather is still pliable, the protrusions ("bulkes" in the professional jargon) are embossed in the leather, four in the head Tefillin, and one in the hand Tefillin.
After the projections are embossed in the leather, they are brought closer to one another (in the head Tefillin), by means of a hydraulic press, and the leather is dried.
In the process of producing the batim from ox-skin, it is essential to dry the batim between each step in the production process. If the batim are not properly dried, the square shape of the batim is liable to be distorted over the course of time.
Only one projection has to be embossed in the hand Tefillin, and, accordingly, the process of its production is simpler.
After the projections are brought closer to one another, the four compartments of the head Tefillin are put in a hydraulic press with a pressure of 12 tons. Metal inlays in the size of the inner space of each of the compartments are then inserted in them. Suitably-sized metal plates are also positioned between the compartments, followed by the operation of a powerful press that applies controlled and equal pressure from all sides. In the professional language, this step is called "press" (in Hebrew too!).
After each step in this process, the batim are examined, to ensure that no external or internal holes have formed. If there are any such holes, the Tefillin are deposited in a Genizah.
Each stage in the production of the batim is followed by a period of at least several weeks, to enable the leather to dry.
In the next phase of the process, the bayit is left to dry for at least two months, when the press is employed once again. The bayit that is formed after the operation of the press is a more exact square.
The next stage is that of grinding and cleaning between the compartments of the head Tefillin. The entire height of the ketzizah is ground and cleaned, to the height of the titora, with a special instrument. This action must be conducted with the utmost care, to prevent the formation of holes in the leather in which so much effort has already been invested. This step greatly improves the square shape of the four compartments of the head Tefillin, and of the entire bayit.
Glue is then inserted between the empty spaces of the titora, and the press is used again to turn the leather of the titora into a single block. Special care must be taken so that no glue will find its way between the compartments of the bayit.
After the gluing of the titora, it is folded under the ketzizah in a special manner that produces the square shape of the titora.