How to make a watch dial
The different steps in making a watch dial on a watchmaker's lathe
I start with a brass disc. The type of brass can be ms58 brass, or CZ120 brass. I actually used CZ120 (typo in the picture).
I mounted the disc on the lathe using a central hole. However, that didn't turn out to be a good practice: so I'd advice to attach the disc on a wax chuck, slightly smaller in diameter than the disc, so that you can easily true the edges and reduce the diameter to size.
When investigating which type of brass to use, I found lot's of confusing information. I finally concluded that for easy turning and malleability, you better have some lead in the brass. These are different forms of brass:
- ms58 brass / CZ121 (CW614N) = CuZn39Pb3
- CZ120 brass (CW612N) = CuZn38Pb2
- c360 brass = CuZn36Pb3 (Cu61Zn36Pb3)
- c356 brass = CuZn39Pb3
- CZ131 brass (CW601N) = CuZn37Pb2
An excellent resource of brass is Ian T Cobb.
Start by reducing the outer diameter to fit in the case, so that it properly rests on the dial rest border in the case.
Then, leaving a thin outer edge, reduce the diameter even further so that the protruding thicker part fits through the dial rest border: this is the part where the index ring will be formed from.
Next, mark the width of the index ring and start turning away the inner mass of the dial. Ensure that the width is large enough for drilling the index holes
Now you see why mounting the disc through its center hole wasn't a good idea: in order to reduce the inner mass thickness, I needed to move the workpiece to a 4-jaw centered chuck. That obviously made the work not run true anymore. Using a wax chuck from the beginning would have avoided that.
Continue reducing the inner mass until it's thin enough for the arbor of the hour wheel to protrude sufficiently.
Once that is finished and the inner disc is turned thin and flat, you can start drilling the index holes, every minute.
I'll detail my drilling setup in a separate post.
My watch movement has a date indicator at 3 o'clock:
- measure the inner and outer distance of the date window and the height on the movement
- mark the measurements on the dial
- drill a hole in the middle of the date window
- square the hole using a file
- regularly fit the dial on the movement to check if the date window has the appropriate size
Now you're ready for polishing the dial:
- polish the index ring to a mirror polish. I use a felt tipped polisher on a micro-motor for that, and the blue and gray Dialux polishing pastes.
- also polish the inner dial the same way as a preparation for the circular graining
- tape the outer ring using polishing tape to protect it from the next step
- mount the dial on a 4-jaw chuck and apply the circular graining, using a Bergeon n°5444 medium coarse polisher: gently push the sponge on the dial while it's turning on the lathe, moving it gradually from the center outwards until a uniform graining is achieved
The basic dial is now finished :-)
Next you need to make the square border of the date window.
I start from a square brass rod, sawing away the surplus material using a jeweller's saw, keeping the necessary thickness for the date window border.
Keep in mind that the hour hand needs to move over the border, so keep it <0.5mm, that should usually do it.
I keep the larger part of the rod attached which makes further manipulations much easier.
Similarly to creating the date window, drill a central hole and file the hole into a square. You can also use a mini mill of course.
I glue the date window into place using a two component glue (Uhu Plus).
You're now ready for attaching the dial feet.
To make it easier to mark the position of the dial feet, I put my movement holder on a mirror so that I can constantly verify if the date is correctly aligned in the date window.
I make the actual markers using a scharp drill bit or milling bit.
I attach the dial feet using a dedicated soldering machine. I got mine at WatchLume. It came with a vial of flux and copper wire of 2 different diameters.
- cut a piece of copper wire of the appropriate diameter and file the end flat, making sure to remove any burrs
- clean the wire, using a soft sanding paper for instance
- position the copper wire on the dial using the clamp
- add a little bit of flux, and 3 little pieces of solder
In this case however, it turns out that the dial is acting as a heat sink and the soldering doesn't go well. The dial feet don't hold. I'll be testing different types of solder to see if they're working better.
I will finish the dial using traditional silver powder, and will revert from galvanoplating. This way the entire process can be done in my own workshop.
Again, I procure my silvering powder from Ian T Cobb.
- First make sure the dial is absolutely clean and grease free by cleaning it in an ultrasonic cleaner, using a general precious metal cleaning agent.
- Then, take a soft damp cloth, dip it into the silvering powder and gently rub it on the dial until a uniform silky silver colour is achieved.
- Wash the excessive silvering powder off under lukewarm water
- Don't let the dial dry! And immediately proceed:
- Take another soft damp cloth, dip it into the finishing powder and gently rub it on until the finish is uniform
- Wash with warm water, and dry quickly
- Ensure that the dial is dust free and apply lacquer or varnish (I use spray lacquer, which I got at Flume, as it specifically mentioned to avoid silver oxidation).
Next on the menu is creating the index dots for the dial. I will be making 12 of them to mark the hours, and will leave the minute dots empty.
I'm using silver steel, which I get from zuJeddeloh.
- turn the dots like you would turn a screw on the lathe, starting with the foot
- regularly check the diameter: it should be just too large to fit in the index hole, as we'll be press-fitting them in
- cut the "screw" loose, using a cut-off graver
- reverse the workpiece, and turn the head flat to the appropriate thickness: I'm using slightly thicker dots for the 12, 3, 6 and 9 markers.
Before polishing the screws need to be hardened. You do this by heating each screw with a blow torch, until glowing red, and then immediately quench in water.
For polishing the dots: pre-polish using a series of lapping papers. I use (40,) 20, 12 and 3 micron lapping paper. I'm still experimenting if I can't skip a step with the same result.
Important to note: attach the lapping paper to a flat, hard surface, like a glass plate. This will ensure that you're polishing only the perpendicular surface of the screw, and avoids rounding the edges. My desk table top is glass, quite convenient.
Don't forget to polish the sides of the screw as well.
The final polishing step is achieving the black mirror polish. You polish using a small amount of diamantine polishing powder (which, basically, is aluminium oxide), mixed with some allround oil. You polish on a zinc block, or tin block. The block needs to be flat and filed slightly rough to take on the grains of the diamantine.
Start by making larger circles, reducing the diameter as you go. For the final rounds you'll be making mini circles and you'll feel how the surface becomes extremely smooth, sliding over the surface of the block.
My quality level is to get the screw head scratch free under a 5.5x magnification.
For final cleaning before blueing I recommend a passage in the ultrasonic cleaner for about 10 minutes, using a general cleaning agent for precious metals.
I'm using the EM700 cleaning agent which I bought at Ultraschall-Welt, together with my cleaning machine.
I'm still experimenting with the cleaning. I usually follow the ultrasonic cleaning with:
- rinse with tap water to get rid of all the cleaning fluid
- rinse with demineralized water, to avoid staining when drying with a puffer
- dip in clean piece of pit wood, and blow off any dust specks
For the blueing it's extremely important that the surface is grease and dust free to avoid speckles. I find that Rodico sometimes leaves a mark, so I avoid it.
Off to the bluing step then. I do it the contemporary way: on a gas stove :-)
To hold the screws I made a brass holder with holes of different sizes. I pre-heat the brass on the stove, turn off the flames, and then place the screws in their holes and observe the colour change until uniformly blue.
As everyone knows who already tried bluing, the outcome can be disappointing, even with screws that shine bright like a diamond.
If bluing fails, then re-harden the screw before re-polishing it.
Finally, press fit the index dots, the screws, in their respective holes on the dial. I use a Seitz jewel press for this job.
Take care not to scratch the blued surface! I tape off the punch to this effect.