Custom watch build #2: “Glass – Parallel”

Note: This was not an exercise in design, but rather an exercise in process.

 

Glass – 42	Glass – Parallel

 

The details:

• Brand & Model: 10/6 Glass – Parallel
• Diameter: 42mm
• Height: 11.1mm
• Movement: Chinese F8131, modified hand-wound
• Power Reserve: 40 hours
• Jewels: 17
• Lume: N/A
• Frequency: 21,600bph (3Hz)
• Crystal: Mineral, Flat
• Water Resistance: 100m/300ft
• Strap: Torro Brava Italian Leather, Black

When I first started tinkering with putting my own watches together, I quickly realized that getting all the components was an issue and then getting all the components to play nicely together was another issue. The primary obstacle I have encountered is the movement holder/ring.

The movement ring is the interface between the movement and the rest of the watch. As I mentioned in [Glass], the key is the holder. After some time and energy exploring different avenues, I have learned that the chances of finding a movement ring that is the right fit between a randomly chosen movement and a particular case are slim to none. Cases and holders are designed and ordered for mass production runs in China, given a particular movement.

For my first watch build, I chose a case that came with a movement holder for common Sellita movements (200, 210, 220). But, that is not what I had initially planned. I wanted to try a cheaper watch movement in a nice case. Specifically, a Chinese F8131 movement in a 42mm stainless steel case from Ofrei.com. Why that movement? It looks ok, tells time, and is $100 less than a Swiss movement.

Of course the F8131 does not fit into the movement ring include with the case since the ring is for Sellita movements. And again, the chances of randomly finding something that works is very unlikely. So what was I to do? Hope to randomly find something on eBay? Try to modify a plastic holder that was somewhat close-to-fit?

As a computer scientist with some technical know-how and access to some useful technology an idea struck me: 3d-printing. Why not take some measurements, draft a modified movement holder with AutoCAD and/or SolidWorks, and print it!

I used the steel movement holder that shipped with the 42mm case as a template and made modifications based on the the F8131 specs that I measured with calipers. Now, 3d-printing is not the most accurate of endeavors on a millimeter scale, but I thought it was worth pursuing just to see if the process would work well enough to allow me to take a chosen movement and create a holder to fit in a chosen case.

To alleviate any suspense, it worked. But it did take several attempts to get the dimensions (tolerances) and process figured out. For example, should the holder be printed top-to-bottom or bottom-to-top, that decision impacts quality. (I found was top-to-bottom was best.) Also, trying different colors, ring thickness, etc. A positive attribute of 3d-printing is the cost. For me the cost is free, but if I were to pay it would be about $0.15 per print. For reference I was printing with an Ultimaker3. And white seemed to work better than black.

Turns out casing screws are fairly standard, so with the standard case screws and a clamp, the F8131 attaches just fine to the custom 3d-printed ring. Chinese movements have a lot more height than Swiss movements, so for the F8131 automatic movement to fit in the case I had to remove the rotor, which is fine. I did leave the rotor plate attached. So my F8131 is now a hand-wound movement as opposed to an automatic movement. I like having a couple hand-wound movements in my collection anyway.

Note the casing screws @ 4 and 10This was a test of process, not design, but for a first run I put a blue minute hand and a red hour hand. The minute hand came blued, but I have also found that an easy and cost effect way to color hands is to buy standard silver and then use a permanent marker to color the hand. The red hour hand is a silver hand colored with a red Sharpie. The shine is maintained and it looks like it was made red.

I need to experiment more with ring colors, hand colors, and straps, but the process works: Given a movement and a case I can 3d-print custom holders. This opens up a lot of possibilities for picking almost any movement and case and marrying the two. I have a couple more movements and cases to work with so my experimentation will continue. Another next step is 3d-printing dials. I do not know if anyone else has tried such things, but the great thing about 3d-printing is that you can create and print anything you want at a low cost, even watch parts.