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School Watch- 6498- Regulateur Complication Part 1- The Crowning Jewels…

Work on my school watch is now back underway, I’m trying to get the majority of the mechanicals sorted before Xmas so ultimately I can focus on the finishing and decoration of the movement/dial. As I have mentioned previously, I’m really keen to have a complication on my watch, mainly to show my watchmaking skills but also to keep the layout of the dial balanced. I decided on producing a watch with a regulateur complication, this displays the hours, minutes and seconds in separate dials.

I produced a functioning prototype just before the summer break but there were a few issues to be solved particularly with regards to the long term wear of the components. I went back to the drawing board and came up with an improved system that would make it into my finished movement. The main areas of improvement included the reduction of wear on both pivots and arbors by utilising jewels along with a more accurate method of positioning the location of the wheels on the main plate. I set to work a few months ago, starting on the main plate to begin with and then moving on to making the other components.

The Original Prototype…

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The main plate needed to be drilled in two places in order to accommodate the extra wheels needed for the complication. There location had to be extremely precise for a couple of important reasons. The wheel which would carry the hour hand from its arbor needs to line up exactly with the fourth wheel pivot in order to obtain symmetry between the sub dials, so the hole for this wheel had to be perfectly positioned. The second wheel needed to take drive from the standard hour wheel in the centre of the movement and transfer it to the wheel carrying the hour hand. The hole for this wheel had to be positioned so that the teeth of all 3 engaged wheels meshed together at the correct depths in order to provide optimum drive and zero slippage.

I used the Schaublin lathe and dividing head to drill the hole for the wheel carrying the hour hand, this way I could ensure the hole would be the same distance from the centre wheel jewel as the fourth wheel jewel was and have it correctly aligned. The hole for the driving wheel was marked using a depthing tool to ensure the teeth of all the wheels would mesh correctly and then drilled using the lathe. The holes were deliberately drilled a lot smaller than required for reasons that will become clearer later on in my post.

The driving wheel on my prototype had an arbor with pivot that turned in the main plate, it wasn’t jewelled and due to my dial also doubling up as the bridge there was no easy way to hold a top pivot. The wear on the pivot/main plate would be minimal as the wheel turns one full revolution every 12 hours but having no secured top pivot was a problem. The wheel would be able to twist, potentially causing it to drag against the main plate or come out of mesh with one of the other wheels. It would be a hard task to make a pivot hole in the dial that didn’t show up on the top side so I needed another solution.

The System to be improved…
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After much discussion and advice, I decided to replace the arbor and pivots with a post that the wheel would turn on, thus doing away with the need to support the top pivot. In addition to the post, the centre of the wheel would be jewelled in order to reduce wear on the pivot and also reduce friction between the main plate and the wheel. My first task was to turn off the tube of an hour wheel and then select a suitable 6498 jewel to fit into the centre that could accommodate a sturdy post. I settled on a centre wheel upper jewel but there was a slight problem…

The space between the main plate and the dial I would be making was set at 0.40mm in order to accommodate the extra hour wheels which are 0.30mm in size. The centre wheel upper jewel was 0.45mm in thickness and would need to be 0.35mm to allow clearance along with lifting the wheel slightly off the main plate. My tutor suggested that I could reduce the thickness of the jewel by rubbing it flat on a diamond lap, I was sceptical but set to work. Amazingly within a couple of minutes I had the jewel down to the correct size, result!

The next task was to ream the centre of the hour wheel out in order to press fit the jewel into the wheel. The Horia jeweling tool has a set of reamers designed for fitting jewels, they ream the hole 0.01mm smaller than the size of the jewel allowing it to press fit into the hole and hold it firmly. After a couple of hours work I had a finished wheel that was ready to use in my movement, the next task ahead of me was to make the post it would sit on.

The Finished Wheel…IMG_3260-1

The post would be made of blued steel and be friction fitted into the main plate. I made the post from a piece of 1.6mm bar, I turned one end down to 0.65mm in diameter and 0.35 in height to accommodate the jewelled wheel as well as giving clearance between the dial. I then used the Horia tool to ream the hole in the main plate to a size that would allow the post to be pressed in and held tight via friction. The hole goes straight through the main plate so the post can easily be removed in the future should repair or replacement be required.

The Post…
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The final task to carry out at this stage was to ream out the hole drilled for the wheel carrying the hour hand to accommodate a fourth wheel jewel. This jewel will house the lower pivot of the wheel and reduce friction, taking the number of jewels in my watch to 19 (Standard 6498 has 17 jewels) and another will be added when the complication is finally completed. I’m still debating whether the twentieth jewel will be visible or hidden…

The Hour Wheel Jewel…
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Anyway thats as far as I’ve got so far, I need to complete the dial that will also double up as a bridge before I can produce the wheel that will carry the hour hand. So far it all seems to be going to plan, the work looks almost good enough to pass as a factory upgrade in my opinion. However, there is still a lot of work to be done, a few tweaks will be needed here and there but its looking like the vision I have in my head which is always good!

How it stands at this point…
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To be continued…

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