Part II - The Case
The case of a watch is really quite a simple thing. A short tube with a cap on one end and a clear glass disc on the front to allow the wearer to see the dial. Come to think of it, the watch generally is a pretty simple thing. Compared to any modern instrument it’s surprisingly basic. The movement is made up of around 130 parts, none of which are very complicated in design. If a watch were scaled up so that the dial was three feet across just about anyone could take one apart, put it back together and expect it to work after. If you had a basic understanding of mechanics and simple tools you could likely make one in a basement workshop.
The tricky bit of these things is the size. They are tiny.
When I first bought the old Omega to fix, I stuck a screwdriver in and realized that I couldn’t see the screw head clearly enough to know whether it had actually accepted the tip of the driver. Some of the screw heads are only half a millimeter wide. The axles in one of my older watches measure only 0.1mm across which, if you look down at a single hair on your arm, it’s about that diameter, give or take, depending on your ancestors choice to buy that cute neanderthal a drink or not.
So the difficulty in repairing these things is being able to see and then manipulate parts that are approaching the microscopic scale. I use a 10x loupe to work on most watch parts, and for some repairs, a microscope is the only way to get close enough to work.
Once you’re able to see the parts the next step is training your hands to move precisely enough to not bull in china shop your way into a mess. It took me months to slow my hands down and not break every watch I touched. I’m still getting better at this discipline and I expect it’s likely something which takes a lifetime to perfect.
For me it’s meditative, I can’t worry about too much in the outside world when it takes all my concentration to move components fractions of a millimeter into their correct places.
Which brings us back to the case.
When I was in highschool my dad decided that book learning was considerably less important than a trade and so I spent half of every school day at a technical college where i was enrolled in a machine tool and die program. It was run by a twitchy fella named Mike who did his best to teach idiot children such as myself how not to cut their fingers off. Along the way I also picked up the basics of how to run a milling machine, a lathe and the rudiments of CAD design. It’s funny how these kind of skills can be taught to a teenager and somehow, despite them not really using them for 20 years, be recalled and applied.
A few years ago I used a few of those skills to design and build a 16x20 large format camera. During that process I learned a new cad program which I kept tinkering with, designing a few bits to 3d print, a folding bed for my camping van, art installation drawings. And when I started fixing the older watches I naturally started doodling up my own.
These doodles eventually morphed into something that looked like this:
It was a case designed around the idea of using as few and as simple tools as possible. Most watch cases have screw down rear case backs. Those require threads and at the scale of those, that would require a very precise lathe. Since I don’t have a shop I’d be relying on makerspaces and their equipment which is generally simple, older and beat to shit. So I settled on the idea of using a spring clip instead. Rather than complex threads it only needs a simple slot cut in the case material to work.
I also had a few requirements for the watch,
1) It needed to look pretty and finished. I’ve seen a few diy watches which look like shit and I didnt want mine to join those ranks. In my art I don’t mind flaws but I like those to be allowed rather than inevitable and unpreventable. Learn the rules before breaking them.
2) It needed to be waterproof and durable, I didn’t want a dive watch but I wanted to be able to snorkel while wearing it and not have to worry about it going all goldfish bowl on me.
3) I wanted to make as much as possible myself.
All this sounded good in my brain and of course looked splendid on the screen of a macbook.
Which brings us up to the rubber hitting the road, the jelly proving its mustard, the goose being stepped on. Making dreams into metal shavings. Building a watch case…
or the case shaping, the lugs which hold the straps and circular part I would need a CNC machine with specialized bits to cut the small radii and didn’t expect to find one I could access so I went back to the experience with the 16x20 camera build and decided to have a vendor waterjet out the rough vertical dimensions. On these I’d include an outer ring which would allow for easy clamping in a lathe.
I chose Stainless 316L alloy for the case material, it’s extremely durable and the same stuff used by the fancy Swiss brands so it must be good. I purchased a bar of it which I took up the lovely folks at Rennline Motorsports for waterjet cutting. They turned a bar into five 60mm discs the next day and even delivered them to a local bar. Service!
Protip: if you want anyone in the machining world to do things faster bribe them with beer. A 18$ four pack goes a long way in speeding a small project up.
I began finding the tools I’d need to make metal cookies into watchlike things. Turns out one needs a lot of tools to make a watch case. Cutters, drills, cutter holders, drill holders. And measuring devices, lots of measuring devices. If you can’t measure, you can’t make.
And then came the cutting, first the back side of the watch, the most complicated and the part that needed to be most accurate. The O-ring seat, snap ring groove and dial shelf. Each cut affects the placement of the other and with something this small even a few thousanths of an inch are enough to ruin the entire piece. Once that was done I replaced the four jaw chuck with a collet chuck and cut down a machinable collet to precisely hold inside the cuts just made to the case. This ensures that the cuts on the front side of the watch align perfectly with those at the rear. Then the front cuts are made.
I’d been somewhat apprehensive about machining the stainless steel as I’d never done anything with the 316 alloy but had been told that it can be difficult to work with. I purchased the best tooling I could afford, carbide cutters with super hard coatings, and the machining was easy and fast. The tolerances of the lathe however, were less compliant. It simply had a bunch of play in all the movements and what should have been a pretty easy job ended up taking an afternoon as I cut, measured, re-cut, adjusted and cut again.
But after several hours I had what looked like a case.
Next weeks installment will be Part III, fitting and fettling where I’ll document the tricky bit of any project, the details. In my case, the minutia of making mechanical objects which work together.
Thanks for reading and I hope you have a great week!
Giles
If you’d like to share with your friends I’ll also add this, along with more photos and video of the build, to my blog here
Oh and if you have feedback on the design or the mailing list (I suspect it’s a bit long for most of you) please let me know. Or just say hello.