CASIO "ReverSIO" MOD

The CASIO brand needs no introduction, in the watch world it is synonym with affordability, durability, precision and sometime fashion (in one expression, you might have heard CASIO being described as a "god tier watch brand" ).

One thing that is quite a bit more niche is that CASIO watches can serve as affordable platforms for custom watches or "mods". In this Instructable, I am presenting my first CASIO watch mod ever.

For context, in the ultra-high-end world of watches an icon can be found in the Audemars Piguet (AP) "Royal Oak" it is a $10k+ watch. CASIO, in their large collection has a model that is affectionately nicknamed the CASIOak in reference to the iconic AP model whilst having a much (MUCH) lower price point.

I personally like the design of the AP Royal Oak quite a bit but there is another watch icon that I like even more, designed and built by another manufacture the "REVERSO" by Jaeger LeCoultre. This watch had the particularity to be able to be easily flipped on its back in order to protect the - then - delicate glass face from damage, when flipped, the cas back is exposed but is made of metal. This instructable is a custom watch case incorporating some elements of the REVERSO for one of the most affordable CASIO: the ubiquitous F-91. This mod make especially sense considering the fact that the original Reverso from JLC included this mechanism as a protection mechanism for the watch face. The Casio F91 also has a watch face that is quite delicate (soft plastic) but a much stronger case back (Stainless steel).

I call this mod the ReverSIO ;)

CASIO F91-W or CASIO A-158 (movement, buttons and face are the same dimensions)

3D models can be found here: https://makerworld.com/en/models/2005685-reversio_v1

1mm steel rod (2x10mm)

3mm steel balls (2x)

3x5mm spring (2x)

SLS printer: I dont have direct access to one so I used SLS 3D printing services online

Glue

Phillips head screw driver

The working principle is quite easy the watch case has a pivot point on one end allowing it to slide into a slit. The other end of the case holds 2 balls protruding out of the case and held in place with 2 springs. When no effort is applied, the case stay in its position. When a side force is applied, the ball are forced inside the case "unlocking" the case that is free to slide in the slit but is also free to rotate along the axis formed by the steel pins. The case is then pressed back in the desired position by the user.

The disassembly of the "organ donor" watch is quite straightforward.

Remove the stainless steel back (keep it aside along with the 4 screws)

Remove the movement by the pulling it straight up - if possible with help of tweezers - (it should be quite easy, if you are using force, you are doing it wrong)

From the INSIDE of the case, one at a time push on the 3 buttons, in the CASIO F-91 (or at least in the modern version) they are "simply" pressed in and can be pressed out (keep these button aside)

Remove the plastic face: this it not easy to do without damaging it, I was in a hurry (or just impatient really) and I did damage mine a little bit, dissolving the glue that hold the face in place could have resulted in a better result.

At the end of this step you should have saved:

1. The steel case back + 4 screws
2. The Movement
3. The 3 buttons
4. The plastic watch face

As explained in the first section, the 2 steel pins slide in the slits on either side of the case, their are made of steel in order not to deteriorate too fast, they have to be inserted in the watch case before assembling the 2 parts of the watch. (Note that I bought long steel rods and I cut them to size right before assembly).

The balls and springs also use the same slit to hold the watch in the position the user choose. This step can be done after assembly of the 2 watch parts but it is easier to do prior to the assembly. (Note that it was easier for me to source 10mm long springs so I cut them in half, precision is not required here, also the springs are in a circular shaft because the side button of the what prevented me to simply use a straight shaft - that would have allowed to use just one straight spring between the 2 balls). The springs are kept in place later on by the movement that covers the spring shafts.

The 3 buttons can also be pressed in place in the 3 holes on the watch case, the button scavenged from the donor watch are exactly the same there is no particular order to put them in. You should press on them a few time to make sure they can move freely without falling out.

The watch case is slid into the the watch holder straight up and from the back. The split in the watch holder is not large enough to accommodate the watch back or even the movement, they are mounted later on.

The watch case is in the "front down" position, you can insert the movement while making sure the button are in the "no pressed" position.

You can close the watch case with the steel case back and the 4 screws. Drive all 4 screws loosely before tightening them all.

Flip the watch case "front up" and glue in the face. Be careful not to put too much glue, you do not want glue dripping inside the case and you do not want to damage the plastic watch face.

You are done with this mod ! All you have to do now is to chose the bracelet (or maybe make one ;) ? )

The bracelet is chosen considering the lug width, if you choose to use my design, I designed the case holder to accommodate 22mm wide bracelets