Introduction: PCB Dial Mod for Mechanical Watch
Some time ago when I looked for design inspiration for the binary wrist watch I did a lot of research and delved deep into the parts of internet home to watch enthusiasts. I came out mostly unharmed, but have now become fairly interested in watches as a hobby.
In this project I will show you how I dissasembled an automatic mechanical watch and made a few daring modifications including a completely new dial. This truly was a project combining a lot of different disciplines as I started off with traditional watch making, which I combined with more cutting edge 3D printing, and PCB design, there's even some good old sewing thrown into the mix.
Read on to see how I took a classic mechanical watch and gave it a completely new dial made from a PCB!
One thing I learned quickly is the large number of specialized tools used in watch making. Most of the tools I used were named just after one single job they did, or one simple part they were supposed to remove. Luckily I picked up some tricks along the way so I could do this project without too many expensive specialized tools, and instead with some cheap office supplies and a 3D printer.
- Seiko 5 SNKK27
- Sewing thread
- Enamel paint
- Sewing needle
- Super glue
- Watch case back remover
- Watch hand remover
- Spring bar tool
- Bic pen
- 3D printer
- Plastic tooth pics
- Mounting putty
Step 1: The Plan
The goal for this project was to take an automatic mechanical watch and make a few modifications to it. The plan to achieve this goal was to first disassemble the watch by unscrewing the case back, then removing the movement which held all the parts I continued to work on.
To work on the individual parts first the hands were removed, then the dial and dial holder. With these bare components I started taking measurements so I could recreate my own parts, and plan how it would all go together again.
The dial would be made from a PCB. To mount the new, differently shaped dial to the movement, I needed to 3D print my own dial holder.
To bring some life and matching colors to the watch I also wanted to add a few splashed of orange, through stitching on the watch band and painting the second hand.
Step 2: Disassembly: the Metal Bracelet
The first step to disassembly was to remove the watch band. At first I was curious about how to remove metal bracelets that sit snug against the watch body. Turns out these are just as easy to remove as most other watch straps, by pushing on the spring bars.
I slid the spring bar tool to the inside of the bracelet and pushed down on the spring bar, while gently nudging the bracelet towards the backside of the watch. When the spring bar poked out of it's previous hiding hole I simply pulled it completely free, and the metal bracelet came off.
Step 3: Disassembly: the Case
The case back, with it's nice display window, is simply simply screwed onto the watch body. I used a tool called a case back remover to unscrew this part. Because the manufacturer screwed this on with some force to keep the watches waterproof, I had to be careful. If I pushed the tool to hard it would slip out of the tiny groves and the polished case could get badly scratches. This problem was remedied in two ways.
First I took my time and applied a steady amount of force to loosen the case back.
Second, I covered the case back in electrical tape to protect against scratches if the tool did slip. Luckily did didn't happen, but it did provide some security.
After the case back was properly loosened with the case back remover I simply unscrewed the rest of it by hand.
Step 4: Disassembly: the Crown
This is the part where I started wearing my white cotton gloves. These protected the delicate mechanical parts against dust and oils from my hands.
To remove the crown I found a super tiny lever to push against. This lever was spring loaded and is what usually keeps the crown from falling out. At this point the crown first had to be completely inserted, as the tiny lever would disappear if the crown was pulled out as if to set the time.
With the lever pushed down I used my gloved fingernail to try and grasp the onto the crown to pull it out. It would have been a lot easier to grab with a pair of tweezers, but I didn't want to use metal (and magnetized) tools where I didn't absolutely have to.
I also used plastic tweezers as the tools that were most in contact with the movement as well, to both avoid any scratches and potential magnetization of the watch parts.
Step 5: Disassembly: the Movement
With the crown removed the movement was no longer held in place inside the watch body. Before I removed it though, I taped down the automatic rotor. This is the part that winds the watch base on the movement of the watch on your hand. Since I wanted the hands to keep still while I worked on the watch I had to keep the rotor from winding as well.
I gently moved the rotor into a position where it protected a few gears from accidental touching, and taped it down with a sliver of masking tape.
Now I used a flat head screwdriver to ever so gently latch onto to movement and lift its edge out of the watch case. Then it was simply a matter of flipping the watch upside down into my hand, and the movement was properly removed.
Step 6: Disassembly: the Hands
Before I removed the hands I reinserted the crown and set the time to 12 AM. This made it a whole lot easier to align the hands in the same position later when the modified watch was reassembled. The reason for keeping the alignment of the hands was to keep the day and date switchover at the same time, at around midnight.
If you make a new dial without the day and date window the hand alignment won't really matter.
Once again I had to use a specialized tool to achieve this step. I used a watch hand remover which can remove all three hands in one simple motion. To avoid scratching the dial, in case I wanted to re-use it some time, I protected the enamel paint by laying down a plastic bag over the hands before they were removed. I used the same plastic bag the watch hand remover tool came in.
Step 7: Disassembly: the Dial
The dial is held onto the movement by two pegs going into a plastic ring. To remove the dial I slid a tiny flat head screwdriver slightly under an opening, just to loosen it. Then I lifted the dial straight up to avoid bending the gentle dial pegs.
My original plan was to 3D print a new dial holder with matching pegs that slid onto the movement in a similar fashion. Because of the tight margins this proved to push not only the limits of my home 3D printer, but that of an industrial 3D printing company I was going to order from. The solution was to ditch the dial pegs altogether on the 3D printed dial holder, but more on that later.
For now I removed the plastic dial holder ring as well, as the new dial holder solution didn't require this.
Step 8: Calculating the Hour Marker Positions
Since the dial was designed completely from scratch in a PCB design program (Autodesk Eagle) I worked with the graphical tools available.
I had full control on placing everything in an XY coordinate system. To properly place and angle the 12 hour markers I had to do some math on their proper positions to make everything look good and shiny. It was time to use our old friend Pythagoras.
I've attached my original sketched calculations along with an Excel document with the coordinates for all 12 hour markers. The approach to problem was to first draw a line to the first hour marker (0, 0) -> (0, r). Here (0, r) are the same as the coordinates (x1, y1).
Then I drew a new line to the second hour marker, angled at 30 degrees (theta) which is 360 / 12. This line went from (0, 0) -> (x2, y2).
r and theta are known variables while x2 and y1 are unknown variables. Remembering our SOH CAH TOA the calculations then become:
x2 = r * cos(theta) = y1 * cos(theta)
y2 = r * sin(theta) = y1 * sin(theta)
Step 9: PCB
With the dial in one hand and calipers in the other I started recreating the original dial in Autodesk Fusion 360. Based on this original dial I then made a new dial that added a few margins on all the important measurements. This just meant I would, hopefully, have an easier time assembling everything later on.
Based on this margin dial I synced the measurements to Autodesk Eagle so I always had an up to date PCB shape based on the 3D modeled dial.
I created a new circuit component in Eagle which was basically just a square pad. This was going to be the hour markers for the dial. These got spaced out based on the coordinates calculated in the previous step.
With the hour markers placed on the dial I ran traces between them, going for an interesting look based on routing commonly seen on regular PCBs. The finishing touches were to add minute markers and some text in the silk screen, as well as adding my logo on the layer for exposed copper.
I ordered the PCBs from PCBWay.com who where kind enough to sponsor this project. They were one of very few manufacturers able to produce the PCBs at the required thickness of 0.2 mm for the watch dial.
Step 10: Modifications: the Strap
Instead of the metal bracelet I wanted to have a black leather band as the watch strap. I found a nice looking strap with some white stitching I really liked, it only needed a bit more life, as if the dial wasn't lively enough, haha.
I removed the white thread with a seam ripper and double threaded regular, orange sewing thread through a needle. This got looped around the hole a few times (three) until i was happy with how the stitching looked. To finish off I tied a double knot on the backside of the strap, cut the thread ends, and hid the knot by pushing it into the hole.
Step 11: Modifications: Painting the Second Hand
To match the orange thread on the watch band I decided to paint the second hand an orange color as well. The second hand was super fragile so I held it by its stem with a tiny clamp while I applied the paint. I used a glossy orange enamel paint which dried with a beautiful finish.
One thing I experienced first hand was how easily the paint could distort the shape of the second hand. I got too much paint on one of the sides. This was simply solved by letting the paint completely dry and then carefully scraping it off with an x-acto knife. I then gave the second hand a new coat of paint, being more careful with the amount of paint this time.
The paint should completely dry and air out before getting assembled inside the watch body. I waited a couple weeks to be completely safe.
Step 12: 3D Printed Dial and Movement Holder
Since the new PCB dial was completely flat without mounting pegs I needed a new way of mounting it onto the movement. The solution was to 3D print an adapter. This has one flat side to be glued to the dial, and another side with mounting pegs and notches that grip onto the movement.
This step involved A LOT of trial and error to get the dimensions just right, so the part could keep the dial completely flush while still letting the rotor spin freely. Luckily you don't have to repeat all of this as you can download the finished 3D file from this step! I'm happy to report this super fine and critical part can easily be reproduced on an inexpensive home 3D printer.
Step 13: Assembly: Dial Holder
Now things are starting to come together. The PCB has a straight white line running down the entire backside. This line matches up with a couple of slits made in the 3D printed dial holder, to make aligning these two parts a whole lot easier.
I carefully aligned the parts and added a few drops of super glue to fuse them together, using a plastic toothpick to smooth the surface of the glue to keep it completely flat.
While the glue dries quickly, I let it air out for another couple of weeks just to be completely sure there wouldn't be any sort of residual glue fumes on the inside of the watch after it was completely assembled.
Step 14: Assembly: Dial
After the dial and dial adapter were glued together, the adapter could be mounted to the movement itself. I started by first aligning the day and date window with the visible day when the watch was disassembled. Then I slid the adapter pegs into two hole on the dial, before pushing the dial completely inside the 3D printed adapter. The adapter will now grip firmly onto the movement.
Step 15: Assembly: the Hands
Reattaching the hands was a whole lot more difficult than removing them. What I learned from some cursory internet research was that mounting putty was perfect for holding the delicate hands while they were reattached. I started by placing down the hour hand, aligning it to 12 AM which was the time set when it was disassembled.
The backside of a regular bic pen worked wonders for pushing the hour hand down onto its stem, as the ink tube had just the right diameter to let the stem inside the tube, while the hand was still pushed down.
The old bic pen trick didn't work for the minute hand though. Instead I 3D printed a solid plastic cylinder and found some copper wire slightly thicker than the hole in the minute hand (the copper wire was 0.75 mm). With a lighter I heated the wire until it was hot enough to melt the plastic, then it got pushed into the cylinder. This created a small indentation I could use to push the minute hand its stem.
The second hand was then fastened by first dropping it into position with mounting putty and a plastic tooth pick, before it got pushed straight down. The second hand only needs to be pressed down with a flat surface, so I used the flat backside of the 3D printed cylinder.
To confirm the alignment of all three hands I observed how everything looked through a macro lens.
Step 16: Assembly: the Case
First and foremost, before any of the parts are put into the watch body make sure they are completely dust free. I gave all parts several hard puffs from an air duster to blow away any stray dust.
With the nice and breathable margins on the dial and movement adapter the whole thing slid nicely into the watch case. I then aligned everything on the inside of the case before pushing the movement further down. The whole movement is held in place by two things: the watch crown, and from the screw in backside. I reinserted the crown and checked if the rotor still spun before moving on to the next step.
Step 17: Assembly: Locking Tight
Now it was time to close everything up. The case back was screwed onto the watch body as hard as I could with my hands, before once again covering the backside with electrical tape. Being real careful I used my case back remover to apply a steady force to further tighten the case back.
Remember, the case back being firmly screwed down is some of what gives the watch its water resistance.
Step 18: Assembly: Watch Band
The final step in bringing all the parts together!
I attached the watch band with some regular spring bars (20 mm). These were inserted into one hole by hand, before closing down the other side with a spring bar tool.
Step 19: Final Thoughts
This beautiful, completely one of a kind, mechanical watch was now finished. I've been wearing it for a while and really like how it looks as it can be worn both in dressy and casual occasions.
There's something really nice about looking at the gently sweep of a mechanical second hand graze across a self designed dial, after getting up close and personal with the complex movement that powers the whole thing.
Second Prize in the