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My first attempt refitting and adjusting pallet stones using shellac


VWatchie
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Intro

A while back I successfully made my first attempt refitting and adjusting pallet stones using shellac. It was something I had dreaded doing (it seemed difficult) but in the end it wasn’t that difficult at all. Having gathered experience from a few years of handling tiny watch parts using tweezers and having developed some left-hand dexterity as well (I’m right handed) probably helped.

Anyway, I thought I’d share the experience with anyone who would be interested and hopefully there’ll be some other WR-talker, now or in the future, who’ll find it useful.

If you’re new to this topic you might find this page and this video on the watch repair channel a good start.

As I didn't want to risk ruining my Gaston tool I melted and prepared the small pieces of shellac on a chisel tool (my improvisation) that I happened to have in my tool box. However, the chisel tool had a very tough plastic y surface but I was able to burn it away to expose the bare metal with my alcohol lamp before melting and forming small pieces of shellac on it.

However, the pieces of shellac needed were much smaller than what they looked like to me in the video. My way of making even smaller pieces was simply to poke the small pieces that I had made with tweezers once they had cooled and were hard.

Setting and adjusting the pallet stones was easier than I thought it would be. I didn't realize the fork slots for the stones pinch the pallet stones (Vostok calibre 2414) and actually keep them in place before the shellac is applied. So, I could replace the pallet stones and then check and adjust the locking depth to the escape wheel teeth before applying the shellac. A bit fiddly yes, and you do need to develop some dexterity with tweezers before you try this but not to the point that you break a sweat. Anyway, thank god for my stereo microscope!

Anyway, it was my first attempt, and as is common when you try something for the first time, I made a mistake. Despite very consciously applying what I felt was a little too little shellac it still flooded the stones and a large portion of the fork when it melted. Also, I applied too much heat so that the shellac started boiling creating bubbles. So, I decided to start all over. Fortunately, the “industrial isopropanol” (so called on eBay) that I have is very efficient so no problem removing the shellac from the stones and the fork. The second time around I only used a minuscule amount of shellac. Also, I heated the Gaston tool holding the fork in short turns, just so that the shellac would fully melt without staring to boil. Much better!

The following is what I would suggest based on my first experience:

Basically, follow the video I linked to above. In the video, Mark pokes and scrapes the fork and the stones with tweezers to get rid of old shellac. I tried that, but it wasn’t very efficient. Instead I would let the pallets soak in industrial isopropanol for about 10 minutes and then use a paintbrush to brush them clean. The shellac dissolves completely in the isopropanol and the stones can then be easily removed and further brushed if required.

To insert or slide a stone back into the fork slot I found holding the fork by the end of the slot (opposite side of where the pallet stone is inserted) with tweezers (left hand) was giving me the most control. I placed the pivot of the fork (guard pin up, of course) in a small hole in my staking block while inserting/sliding the stones with another pair of tweezers (right hand) into the slots.

After having applied the shellac Mark suggests re-heating the shellac to adjust the stones. I was worried that it might result in a mess if I tried it, so I decided to do the adjusting before applying the shellac as shown in this video. The slots for the stones pinch the stones pretty well so if you're careful while you're testing the lock to the escape wheel teeth this method works well and won't dislocate the stones. However, to make sure, double check the positions (depth and angle) of the stones before applying the shellac.

Now, the tiny piece of shellac should be placed on the rear section were the stone meets the fork. Mark is clear about this in his video but for some reason it completely passed me by when I made my first attempt. In my second attempt I followed Mark's instruction, but the piece of shellac, being very asymmetrical in shape, was difficult to place in the right spot. However, after warming the pallets to the point that it had only softened the shellac a bit, I discovered, to my surprise, that I could manipulate the shellac into the perfect spot with the tip of my tweezers, without the shellac sticking to the tweezers.

Of course, as I've come to realize, every repairer must find his or her own way, but hopefully you'll find my "discoveries" useful. Above is a picture of the result. It's not perfect but still worked very well. The amount of shellac on the entry stone is a bit too little, and there is a < 1 degree tilt on the exit stone (which, of course, can’t be seen in the picture).
 

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  • 4 weeks later...

Servicing my 2nd Omega cal. 268 (service walk-through for my 1st here) I wasn't too happy with the state of the shellac holding the pallet stones in place. The shellac had crackled quite badly and some pieces had fallen off. So, I decided to remove and refit the pallet stones, and in the process I made a few more observations and experiences I'd like to share.

1. Removing the old shellac was not as easy as just soaking the pallets in isopropanol and brush it off. The shellac just wouldn't dissolve. The shellac only softened somewhat in the isopropanol despite leaving it in for over 30 minutes. So, I had to scrape the shellac out using pegwood dipped in isopropanol, and I even had to poke some sections of the fork slot with my most pointed tweezers (being very careful not to scratch the fork). My newly bought fresh shellac dissolves completely in isopropanol in about 10 minutes. I estimate that the old shellac was almost 60 years old and perhaps it is the case that the chemical composition of old shellac changes over time so that it becomes harder and less susceptible to isopropanol!? In that case, it explains why it is sometimes possible to rinse the pallets in isopropanol without the shellac softening, while at other times it leads to the shellac becoming very soft and soggy dislocating the pallet stones.

2. I wasn't sure it was the case that the fork slots always, or most of the time, pinch the pallet stones, but I have since then learned that the stones should always fit snugly in the slots. The exception I believe might be some very old pocket watches. Well, the point being that we can adjust the locking depth of the stones to the escape wheel teeth (as shown in the video I linked to in my previous post) before fixing the stones with shellac as long as we're being gentle.

3. I found a more efficient way to create small pieces of shellac of a more convenient size by heating the end of my shellac stick until it starts to glisten and then stick the end of a small piece of pegwood (2 mm in diameter) into it and pull out a tapered string of shellac. As long as the shellac is warm you can basically pull out a string as thin as air. Anyway, when the string is tapering from about 0.5 to 0.1 mm I stop pulling, let the shellac cool and break off the string. After this I use the tip of a sharp scalpel to cut the string into small conveniently sized pieces.

4. The Gaston tool mentioned in my previous post proved to be more useful than I first thought. As it firmly holds the fork in place it makes it easy to refit the stones by sliding them into the slots. So, no need to hold the fork steady in a staking block using tweezers held by the left hand (which feels a bit scary really). Also, the arms of the Gaston tool really makes it easy to push the stones into the slots in a very exact manner.

I think that sums up most of what I learned doing this operation the second time around. So, hopefully it will be useful to present and future WR-talkers who are in the process of learning this technique.

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3 minutes ago, VWatchie said:

 

 

3. I found a more efficient way to create small pieces of shellac of a more convenient size by heating the end of my shellac stick until it starts to glisten and then stick the end of a small piece of pegwood (2 mm in diameter) into it and pull out a tapered string of shellac. As long as the shellac is warm you can basically pull out a string as thin as air. Anyway, when the string is tapering from about 0.5 to 0.1 mm I stop pulling, let the shellac cool and break off the string. After this I use the tip of a sharp scalpel to cut the string into small conveniently sized pieces.

We were taught in school to do just as you've done here, with one simplifying step: when you have your shellac strand on your pegwood, break it off leaving 2-3 mm. Now you have a shellac applicator. Heat your fork, and apply the shellac directly with the shellac-tipped pegwood. You very quickly learn how thin to pull it to have a useful "tip". This is done with sharpened pegwood.

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  • 1 month later...
  • 3 months later...
Posted (edited)

Conclusion

I have found that acetone is the most efficient chemical (that I have tested) to quickly dissolve shellac. It dissolves the shellac into a soft jelly-like substance in seconds. The label on my bottle of acetone says: "Remover. Acetone with oil. Removes tough varnishes such as glitter varnish, acrylic, and gel." It's a Swedish brand named "Gripen", but I guess any brand or type of acetone will work the same.

Background

Some time ago I serviced an ETA 2836-2 movement (my service walkthrough here). I found this movement in a bag with various spare parts and quartz movements that I had picked up on tradera.se (Swedish local eBay) for about €30. To my surprise it was complete and looked liked it had never been serviced or tinkered with, and it wasn't overly dirty. However, despite being wound up, it wouldn't tick for more than a couple of seconds. Upon closer inspection I discovered that the pallet stones were covered in some black and very sticky substance. What surprised me was that this black goo was not present anywhere else in the movement. Makes you wonder! Out of curiosity, if you have any ideas about what this black goo might have been, please let me know!

To get rid of this black goo I tried with Horosolv degreaser which usually is amazing (in my experience more potent and clean than naphtha and lighter fluid which I no longer use) but this time around it didn't do a perfect job. So, I thought I should try with vinegar essence (excellent rust remover, and you never know) and acetone. However, as I had no idea how these liquids would affect the shellac holding the pallet stones in place, I first dipped some shellac into each liquid to see what would happen. After this I concluded that vinegar essence doesn't affect shellac at all (nor Horosolv degreaser), but acetone dissolves shellac into a soft jelly-like substance in seconds. Isopropanol can also dissolve shellac (depending on its age, I believe) but not as efficiently as acetone.

So, the next time I need to remove old shellac from pallet stones I'll be using acetone.

Edited by VWatchie
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To remove nail-polish the ladies sometimes use (fancy brands) $$ nail-polish-remover. That's another way to make money with acetone.

If your live is dear, consult your wife first before using her acetone nail polish remover  😆

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5 hours ago, Endeavor said:

If your live is dear, consult your wife first before using her acetone nail polish remover  😆

Or you can visit one of our Swedish stores none of us visit but still have all their products at home.. a clue   😉
Aceton_Biltema.thumb.jpg.a8812e9e019048980d136173fa27915c.jpg

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