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6498 School Watch- Fine Horological Craftsmanship- Snailing the Crown and Ratchet Wheels

I had decided a long time ago that I would decorate the ratchet wheel and crown wheel on both of my school watches. Having watched last years students struggle to produce a finish of a high enough quality for my liking, when snailing their wheels, I favoured finishing mine with starburst grain. I wanted to have a finish that was of a high standard and if I couldn’t achieve that with complicated techniques I would just give them a basic grained finish.

Towards the back end of last year a couple of the other students in my class decided they would like to attempt some snailing and asked if I wanted to get involved. Last years attempts were pretty flawed due to the lack of any guidance and as a result the method chosen wasn’t quite right. This year was a little bit different though, one of my fellow students had discovered some videos created by a watchmaker in Germany and in these videos it demonstrated how to snail wheels. His name is Steffen Pahlow.

The process basically involves rotating the wheel, a round piece of bar that is also rotated is then brought into contact with the wheel and the result should be some kind of circular grain. We decided that if we could create some similar tools to do the job and replicate the process we would get some great results. There would obviously be a lot of trial and error involved as with attempting anything for the first time, especially when the video didn’t explain every little detail. Things like lathe speeds, width of the tool, etc would have to be figured out amongst ourselves. It would be a tough task but we had a few days of spare time so we decided to give it our best shot.

An example of snailing on a German Dornblueth movement…
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The first thing we needed to do was make the tools required, something to hold the wheels and something to create the snailed effect. Taking inspiration from the video we decided to use a section of solid brass bar to create the holder and the snailer. Some trial and error followed and we ended up with two holders- one for the crown wheel and one for the ratchet wheel. Two holders were required due to the wheels having different sized holes in there centres. The holders are designed to fit into a collet on the Schaublin lathe, they are basically a round piece of bar with a peg in the centre to locate the wheel, shellac is then used to secure the wheel in position.

The ‘snailer’ is basically a round piece of bar designed to fit into another collet located in the milling attachment on the lathe. Our initial design was just a flat piece of bar but we later modified it by turning the centre of the bar out to leave a small lip on the edge for reasons I’ll explain later. This is the most important tool because effectively its what creates the circular grain and eventually the snail effect.

With the tools completed, the next step was to set up the lathe and secure the wheels on there respective holders. We needed to use the cross slide with the milling attachment to allow us to move the ‘snailer’ across the wheel and also to enable it to rotate. The ‘snailer’ was positioned at the same height as the wheel and so that it overlapped exactly half of the wheels diameter. Once we were happy that everything was positioned correctly we started the lathe running and put the wheels into contact to see what would happen. We soon ran into our first problem…

The factory ratchet and crown wheels weren’t completely flat! A a result the ‘snailer’ had to be moved further and further into the wheel to wear down the surface until was completely flat.
Our initial design of ‘snailer’ was just a flat piece of bar and because it had to be in contact with the wheel for so long to make it flat, it created too much friction resulting in the shellac overheating and crown/ratchet wheel working itself loose. To overcome this we modified the ‘snailer’ so that only a small lip on its edge came into contact with the wheel, this significantly reduced friction and 9 times out of 10 the wheel stayed securely in position.

The lathe setup…

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We came to the conclusion that this was probably one of the main reasons last years students failed, not due to the wheels coming loose (they secured them with screws) but due the huge amount of friction creating large amounts of vibration. It’s nearly impossible to get an even finish and a crisp line between the rings of graining that create the snail effect when there is so much vibration.

Once we had modified the ‘snailer’ and made the wheel flat we could start the graining. What followed was a lot of trial and error with speeds, direction of rotation and varying grades of abrasive pastes. The idea being to get the optimum circular grain. What we wanted was a fine coarse grain on close inspection and a hint of light reflection from a distance. After a couple of attempts, we stumbled across the right combination of speed and direction of rotation, the result was pretty impressive but we believed we could improve upon it by using a slightly different grade of paste. Another few attempts later and we had cracked it, we were left with a wheel sporting a perfect circular grain and we could move on to the next stage.

The so called snail effect is basically two rings of circular graining which run in opposite directions to each other. The result is a snail like pattern when viewed from a distance in the right lighting conditions. You could call it an optical illusion of sorts. It’s a high end finish predominately used by a number of the German watch manufacturers. Like most of these finishing techniques the method used to obtain them is a closely guarded secret so we were fortunate to stumble across the you tube video by Steffen Pahlow.

To create the snail, the ‘snailer’ is moved outwards from its central position on the wheel, the amount it’s moved is dependent on what size you want the two grained sections of the snail to be. We decided to start further out than we wanted, this way we could move the ‘snailer’ inwards until we achieved the width that looked the best. It was much easier this way because if the widths weren’t right we could just move in a bit more instead of starting all over again. The ‘snailer’ is then rotated in the opposite direction to the one it turned in previously. If all has gone to plan we are left with two rings of circular grain divided by a crisp line that give the illusion of a snail pattern.

A before and after…
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This finish helps take the perceived quality of a movement to the next level in my opinion. I like the fact that snailing is not used in the same way as Geneva stripes or pearlage which are often used to decorate mass produced movements from the likes of ETA, etc. I am trying to achieve a high standard of finish on my movement and its these small areas of decoration that are key to me achieving this. I’m really pleased with the end result, it was well worth all the effort and showed that a little guidance combined with some trial and error goes a long way. I now have a set of finished wheels for both of my movements but I will probably experiment with a few more variations before deciding on the finished wheels for my movement.

A closer look…
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I think you will agree that these snailed wheels look a thousand times better than the factory ETA wheels. The experience has also given us the confidence to experiment with some Geneva stripes on our bridges so look out for a post on this in the near future! Thanks for reading if you’ve got this far and I hope you will continue to follow my journey.

The video that made it all possible, thanks Steffen!

http://m.youtube.com/watch?v=S_S8oA9HdlY

I also have to thank Abraham Altairy for use of his pictures as I haven’t managed to take any good quality ones of my own!

Posted in The British School of Watchmaking and tagged , , , .