skeletonising, Part3

So I have cut out most of the material with a fretsaw. Now the plates and bridges must be filed down with needle files to the required shape. You can see needle files in the picture below.

This is a very delicate task. The part must be held in a vice so that one can file it and yet the vice must not damage the part. Crushing the part, pushing in a steady pin etc. are potential hazards at this stage. Also, filing must be done carefully. Thin areas can be distorted by filing, so these need some sort of support. Any mistake and the watch will not work. This is why skeletonising is more than just sculpture. In the end the watch must work and keep time!

A few days of careful filing results in this, the bridges....

... and the dial plate.
Everything look fine, except ......... please see the next few images...........



As you can see, the flanks of the bridges look terrible. The file gives you the correct shape but the surface that has been filed is quite unsightly.

A few more days of sanding the flanks with emery paper stuck on brass strips and this is what you get.......



..... a nice, even brush finish.

Next, we deal with the inner surfaces. hope you enjoyed this.

Aditya

Skeletonising, Part2

The moment of truth; time to put saw to movement!!!

Well, not quite. Before that I need to transfer the design onto the plates and bridges. I made a template on a polypropylene sheet. This allows me to see through the template (very important if you want to align about two hundred microscopic holes!)
Then I drill holes at all the corners.

Next, I play connect-the-dots with the fretsaw.

This is the beginning of material removal. I leave lots of margin. Even so, the final design is faintly visible at this stage. Here is the dial-plate....

....and the bridges.

There is lots of filing to be done!!!

Aditya

Skeletonising, Part1

So after all the preparation and making new parts we come to a not-too-unimportant aspect of making a skeleton watch, Skeletonising :-)

Here is a 'before' picture of the movement
Of course, the movement needs to be disassembled. Here is a picture of only the bridges & plates.

The first thing I do is fix the dial on to the movement. It is important to do this now. The alignment will be difficult once most of the material has been removed. This is the reason why I made all these parts before I touched the movement. in the picture below you can see the dial plate in the movement ring.

Now the dial is placed on this assembly & aligned properly. Markings are made at the 12 & 6 o'clock positions; small diameter holes are drilled; and these holes are broached till the dial markers go through. If you look carefully, you can see the markers in the picture below (sorry for the poor quality image)

Here, I would like to talk about the way dials are mounted on the movement in most watches (including the one that donated this movement). I think it is safe to say that 99 % of watches today have dial feet soldered to the undersides of the dial. These go through holes in the dial plate. Screws in the periphery of the movement press onto the dial feet and hold the dial in place. All ok so far, except that I have seen too many vintage & antique watches with broken dial feet and dials floating about in their cases.

This is the reason why in No.1 I have made the 12 & 6 o'clock markers go through the dial & main-plate. On the other side I will drill a small hole in the dial marker & put a brass taper pin through it to hold the whole assembly together. All will be clear when I actually do it & post pictures.

Anyway, a small problem cropped up. The hole for the 6 o'clock marker was too close to a feature on the edge of the movement. So I had to fill the feature up. You can see the filler ( brass coloured) in the picture below.

This is held in place with a screw. I made the screw out of an old, rejected dial marker. So I am a happy man :-)

In the next post, I will write about actually starting the skeletonising. Perhaps this post should have had a different title :-)

Aditya

The Hands Part3- The Minute Hand

In a skeleton watch the hour hand is held in place by the minute hand. In regular watches the dial does this job. This complicates the design of the minute hand a little bit. What is required is a sort of pipe or collar below the hub to keep the hour wheel engaged with the minute wheel. Hands are also made in two pieces, a turned hub & a thin filed hand. But I wanted the hands for No.1 to have a little more 'meat' on the bones. Therefore these hands are one piece.

As with the hour hand, a hole is drilled & the job is mounted on a turning arbour. But in this case, a sort of 'island is turned at the hub.
The material around this island is filed away.....

..... and the hand is shaped a bit.

Now the protruding collar is turned down a bit.....

... and the inside is turned away to accommodate the cannon pinion.

Here is what the collar looks like.

The hole is broached to fit the cannon pinion.

Now, the hour wheel is 'cleaned up' and hour hand broached for a good fit.


And, finally, a test fitting of the rough hands on the movement.

I can finally begin the skeletonisation. Hope this was interesting.

Aditya

The Hands Part2- The Hour Hand

The Hour hand for No.1 is fairly easy to make. Essentially, it is a flat piece of steel with a hole and a certain shape around the hole. The minute hand is more complex. But we shall come to that in due course.

The first thing to be done is to drill a pilot hole for the hub. This is always smaller than the required dimension and with the planed side facing down. The idea is that, provided the set up is true and rigid, the surface & the hole are perpendicular.
The job is mounted on a suitable turning arbour. In the picture below you can see a set of vintage turning arbours I acquired some time ago. These allow you to turn jobs with holes of various diameters.

Now, the correct diameter for the hub is marked on the turns.

Here it is, I like to make a marking on both sides. Also, the hole has been broached to fit the hour wheel.

The hub and the rest of the hand is filed down. Please note that the dimensions are on the larger side since some more material will be removed during final adjustment & polishing.
Finally, both the surfaces are planed once again on the polishing tool.
The rough hand is ready. It is still soft. The hand will only be hardened & tempered after final adjustments.

Aditya

The Hands part1- Preparing the Material

After all the excitement about Switzerland, lets get back to the watch!

No.1 has blued steel hands. You cannot just use any steel. Functionally the hands need to be tempered to spring. This allows for repeated assembly & disassembly (during servicing). Also, a spring retains its shape better. Aesthetically, they need to be heat blued. Silver steel serves this purpose very well. Unfortunately, I have only been able to get it in rod form. So, I must make flat bars out of the rods.

Here are two lengths of rod, one for the hour hand, one for the minute hand.
These need to be split down the middle.

The two halves...

The halves need to be filed down into bars with parallel surfaces

In watch work, a good finish is essential at each stage of work. Here are the bars ready to be worked upon.

Next time I will write about making the rough hour hand.

Aditya

Neuchatel Part2- WOSTEP

For all it's reputation, WOSTEP turned out to be a very unlikely place. It is a charming former house on the lakeside road. I was told it was built in 1907. I had expected a high rise set-up humming with activity. Instead it is a very cosy place with just 6 students in the 2 year full training programme. It is obvious they focus on quality :-)

Since I have got prior experience with watches my test was a little different. The others were asked to file a block of brass into as perfect a cube as was possible. I, on the other hand, was asked to service an ETA 2892. This is an automatic movement with (quick-set) date complication. I had never worked on this movement before. It has some unusual features e.g. the winding gears & the offset train. So, I took quite a bit of time to do this task. I am happy to say that the movement was working after I was done with it :-)

The next task was to cut a piece of brass in a 'V' shape.
like this....
And then it had to be filed so that it matched perfectly, one way......

...or the other.
Looks easy but it takes a lot of careful filing to get the two pieces to match perfectly. If the job is well done, one should not be able to see any light gaps between the two pieces.

For the last task, we were given a couple of hairsprings & tweezers.

We were asked to form numbers from 0 to 9 with the hairsprings. This was probably the most delicate task. Hairsprings have a mind of their own & there is a knack to getting the shapes one wants. Here is what I managed. In my defence I will say that my handwriting is terrible as well :-)

Apart from these three tasks, we had to fill out a questionnaire with some maths problems and questions on gears & levers. So that is what the two day test was like.

Aditya