Replacement jewel question

[ifibrin]

I was wondering, when replacing a jewel in a watch mainplate or bridge, how common is it to have to ream/broach out the hole to a larger size? I don’t have any jewel assortments, so I would have to buy a replacement jewel from Seitz anyway, and these come in 0.1mm increment. Do the original holes for jewels in the mainplate/bridge go in the same increment, like 0.59mm, 0.69mm, 0.79mm, 0.89mm, etc.? Or are the original holes for jewels in random diameters, such as 0.73mm, 0.84mm, 0.96mm, etc., making reaming/broaching the original hole a necessity in order to fix Seitz jewels.

Also, are the pivot sizes, and jewel outer diameter for mainplate the same for the bridges in the same movement? Meaning it would be possible to obtain a scrap bridge, and if the jewels are still good, press the jewel out from the bridge to be used in the mainplate? I would imagine obtaining a scrap bridge for jewels may be simpler than tracking down a single jewel of the correct size.

[nickelsilver]

Ideally you don't ream the hole; you have a replacement jewel that is the same size. If reaming is necessary, it's best to do as little as possible. Jewels are standard in industry in that they do (with very rare exception) stick with nominal sizes in 0.10mm increments in the smaller sizes, with the jumps getting more spaced out in the larger diameters.

 

Jewels for the same component are often different diameters for mainplate and bridge. Often smaller on the mainplate.

[ifibrin]

57 minutes ago, nickelsilver said:

Ideally you don't ream the hole; you have a replacement jewel that is the same size. If reaming is necessary, it's best to do as little as possible. Jewels are standard in industry in that they do (with very rare exception) stick with nominal sizes in 0.10mm increments in the smaller sizes, with the jumps getting more spaced out in the larger diameters.

Hmm… does that mean that people ream the holes for jewels because their jewel assortments just don’t happen to have the right OD? I went to check the Bergeon catalogue, and it seems that for a price, you can get almost all the jewels with the right OD and pivot size.

[nickelsilver]

18 minutes ago, ifibrin said:

Hmm… does that mean that people ream the holes for jewels because their jewel assortments just don’t happen to have the right OD? I went to check the Bergeon catalogue, and it seems that for a price, you can get almost all the jewels with the right OD and pivot size.

One of the big selling points of the Seitz tools and jewel sets was for replacing jewels in old watches that had rubbed-in jewels. There you definitely need to ream the hole out to a larger size. Unfortunately that usually meant a much larger size, and the repair was rather ugly, so most good repairers try/tried to replace with another rub-in jewel if possible*.

 

But more commonly, and to answer your question, yes, often one will ream a size or two up simply because they don't have the appropriate jewel on hand, or it doesn't exist in the set or at a supplier. If you look at the chart there are many gaps in external diameters; I am quite sure that in the past there were more sizes available, but even old very complete sets don't necessarily have every single diameter for every hole size.

 

*I have loads of old rub-in jewels, but they tend to be in random assortments, and even if you luck out and find one that fits the pivot size it very likely won't be the right outside diameter- and even then, they are often too thick or too thin to set correctly. To do a tidy repair I will often turn a bushing that fits the original setting, with an appropriate hole for a friction jewel, and fit it all up. If done with some care the repair is usually almost invisible, other than the fact that many older jewels are more pinkish, and new ones a deep red.

[Neverenoughwatches]

6 hours ago, nickelsilver said:

One of the big selling points of the Seitz tools and jewel sets was for replacing jewels in old watches that had rubbed-in jewels. There you definitely need to ream the hole out to a larger size. Unfortunately that usually meant a much larger size, and the repair was rather ugly, so most good repairers try/tried to replace with another rub-in jewel if possible*.

 

But more commonly, and to answer your question, yes, often one will ream a size or two up simply because they don't have the appropriate jewel on hand, or it doesn't exist in the set or at a supplier. If you look at the chart there are many gaps in external diameters; I am quite sure that in the past there were more sizes available, but even old very complete sets don't necessarily have every single diameter for every hole size.

 

*I have loads of old rub-in jewels, but they tend to be in random assortments, and even if you luck out and find one that fits the pivot size it very likely won't be the right outside diameter- and even then, they are often too thick or too thin to set correctly. To do a tidy repair I will often turn a bushing that fits the original setting, with an appropriate hole for a friction jewel, and fit it all up. If done with some care the repair is usually almost invisible, other than the fact that many older jewels are more pinkish, and new ones a deep red.

Not a good idea to make even a small reduction to the pivot to accommodate a tight jewel hole ? Any guide to the sort of side shake expected? 

6 hours ago, nickelsilver said:

To do a tidy repair I will often turn a bushing that fits the original setting, with an appropriate hole for a friction jewel, and fit it all up

Is the bushing also a friction fit ?  I've noticed externally threaded bushes, are these something you use nickel ?

[HectorLooi]

14 hours ago, ifibrin said:

Hmm… does that mean that people ream the holes for jewels because their jewel assortments just don’t happen to have the right OD? I went to check the Bergeon catalogue, and it seems that for a price, you can get almost all the jewels with the right OD and pivot size.

That is just their chart but does any supplier have stock of the size you need?

I have also adjusted the OD of a jewel to fit a hole. The outer edge doesn't need to be that well polished anyway.

[ifibrin]

1 hour ago, HectorLooi said:

That is just their chart but does any supplier have stock of the size you need?

I have also adjusted the OD of a jewel to fit a hole. The outer edge doesn't need to be that well polished anyway.

Actually, as long as there’s a Bergeon supply number, any Bergeon distributor can bring it in for you. Only question is if the distributor wants to order it in, and it can take quite long.

How did you adjust the OD of a jewel while maintaining the pivot hole concentric? Did you use a watch lathe?

[HectorLooi]

27 minutes ago, ifibrin said:

Actually, as long as there’s a Bergeon supply number, any Bergeon distributor can bring it in for you. Only question is if the distributor wants to order it in, and it can take quite long.

How did you adjust the OD of a jewel while maintaining the pivot hole concentric? Did you use a watch lathe?

Yes, you'll need a lathe. I use shellac to stick the jewel to a brass rod and centre it. Then use a diamond file to rough out the OD. And finish with diamond paste of diminishing grits. I think @jdrichard has several videos on adjusting jewels.

[ifibrin]

Just now, HectorLooi said:

Yes, you'll need a lathe. I use shellac to stick the jewel to a brass rod and centre it. Then use a diamond file to rough out the OD. And finish with diamond paste of diminishing grits. I think @jdrichard has several videos on adjusting jewels.

Wow. Do you use optical centering with a microscope for the lathe? I can’t imagine a wobble stick would work for a jewel.

[HectorLooi]

9 minutes ago, ifibrin said:

Wow. Do you use optical centering with a microscope for the lathe? I can’t imagine a wobble stick would work for a jewel.

Actually it's not that complicated. Go watch some YT videos on how it's done.

[ifibrin]

58 minutes ago, HectorLooi said:

Actually it's not that complicated. Go watch some YT videos on how it's done.

I don’t have a lathe or a microscope, so I can’t try either… but I’m impressed! Can you really grind down a jewel to an exact OD? You could start a business selling custom jewels!

[HectorLooi]

23 minutes ago, ifibrin said:

I don’t have a lathe or a microscope, so I can’t try either… but I’m impressed! Can you really grind down a jewel to an exact OD? You could start a business selling custom jewels!

Haha.

Filling a tooth is quicker, easier and pays better.

[nickelsilver]

12 hours ago, Neverenoughwatches said:

Not a good idea to make even a small reduction to the pivot to accommodate a tight jewel hole ? Any guide to the sort of side shake expected? 

Is the bushing also a friction fit ?  I've noticed externally threaded bushes, are these something you use nickel ?

I don't mind taking off just a little from a pivot bit if really needed. 10% would be the most I would be comfortable with.

 

Like Hector says, you can adjust jewels if needed. It's a bit hairy going at them with a diamond file, it does work, but sometimes the jewel ends up with the outside eccentric or out of round, even using a lathe. Best is using the lathe, and then a diamond grinding wheel in a live head (milling attachment). If taking of just a few hundredths the file is probably ok. When I need to make an entire jewel from scratch I get out the really cool stuff, haha.

 

That's a magnetic chuck in a larger bench lathe, with a sub chuck on it that takes 8mm collets, microscope to check centering. With this setup I can shellac the jewel on pretty centered, then center up perfectly with the magnet at low force, then turn on magnet, and can grind the outside and drill (grind) the hole, make the dome and sink. A lot of work though, from scratch.

 

 

 

[ifibrin]

29 minutes ago, nickelsilver said:

Best is using the lathe, and then a diamond grinding wheel in a live head (milling attachment). If taking of just a few hundredths the file is probably ok. When I need to make an entire jewel from scratch I get out the really cool stuff, haha.

That’s really cool. I assume the giant lathe in the picture you posted is not a normal watchmakers lathe?

I notice that in the Bergeon jewel catalogue, there’s a missing entry for pivot 0.09mm, jewel OD 0.90mm. In your experience, which would be easier to do: make a brass bushing for a jewel with OD 0.70mm so that it has OD 0.90mm, or use a lathe to grind down a jewel with OD 1.00mm to OD 0.90mm? Or just make a jewel from scratch?

I assume in a high grade watch, you wouldn’t want to ream out the hole for the jewel. Or in cases where a jewel is held in the mainplate by an incomplete U shaped cut-out, as in the mainplate third wheel jewel of tiny ladies movements.

Edited May 25, 2022 by ifibrin

[nickelsilver]

9 minutes ago, ifibrin said:

That’s really cool. I assume the giant lathe in the picture you posted is not a normal watchmakers lathe?

I notice that in the Bergeon jewel catalogue, there’s a missing entry for pivot 0.09mm, jewel OD 0.90mm. In your experience, which would be easier to do: make a brass bushing for a jewel with OD 0.70mm so that it has OD 0.90mm, or use a lathe to grind down a jewel with OD 1.00mm to OD 0.90mm? Or just make a jewel from scratch?

I assume in a high grade watch, you wouldn’t want to ream out the hole for the jewel. Or in cases where a jewel is held in the mainplate by an incomplete U shaped cut-out, as in the mainplate third wheel jewel of tiny ladies movements.

That's a Schaublin 102, it has twice the center height of a standard watchmaker lathe. Considered huge by most watchmakers, but tiny to most machinists, haha.

 

If setting a jewel in a bushing, you have to consider the wall thickness of the bushing. To fit a 0.70mm jewel, you'd want a wall thickness of at least 0.25mm, so the bushing would need to be like 1.20mm. To answer a previous question- if making a bushing to fit a rub-in setting, I shape the bushing to suit the setting, and rub it in, if possible. Making a jewel from scratch is a big job- I will always modify a jewel if needed and a jewel that will work is available. The setup above was from a marine chronometer jewel I had to make, which was 3.30mm, with a huge dome and oil sink, and relatively tiny hole of 0.18mm. No chance of finding one, or one that could be modified.

 

On modern (mostly ETA) where they have that tiny jewel held by almost nothing, there's not much you can do. Those are very oddball jewels, and are so small for a reason, so fitting anything else would be very difficult. Some similar movements use a bushing there, that is sort of hourglass shaped, and the whole thing is pressed in to a correspondingly shaped cutout in the plate. When I see a worn one of those (often), I make a new whole bushing, in beryllium copper, which will wear much longer than the original brass. But I do that with a CNC milling machine.

[Neverenoughwatches]

2 hours ago, nickelsilver said:

I don't mind taking off just a little from a pivot bit if really needed. 10% would be the most I would be comfortable with.

 

Like Hector says, you can adjust jewels if needed. It's a bit hairy going at them with a diamond file, it does work, but sometimes the jewel ends up with the outside eccentric or out of round, even using a lathe. Best is using the lathe, and then a diamond grinding wheel in a live head (milling attachment). If taking of just a few hundredths the file is probably ok. When I need to make an entire jewel from scratch I get out the really cool stuff, haha.

 

That's a magnetic chuck in a larger bench lathe, with a sub chuck on it that takes 8mm collets, microscope to check centering. With this setup I can shellac the jewel on pretty centered, then center up perfectly with the magnet at low force, then turn on magnet, and can grind the outside and drill (grind) the hole, make the dome and sink. A lot of work though, from scratch.

 

 

 

Thank you Nicklesilver. That is some pretty cool stuff and the level of skill involved i would imagine way beyond what most of us here would ever achieve. Fascinating nevertheless and possibly gives us a different approach to what we could manage. I'm Interested to hear how you go about bushing and what equipment is most suited for the job mostly. This sounds like an easier solution that a lot of us might be capable of.

[ifibrin]

3 hours ago, nickelsilver said:

That's a Schaublin 102, it has twice the center height of a standard watchmaker lathe. Considered huge by most watchmakers, but tiny to most machinists, haha.

Wow, you have access to tools, and have skills most of us can never hope to achieve in our lifetime. Would you be ok sharing how you managed to make this your career path? You can ignore this if it’s too personal.

Anyway, in the Bergeon catalogue I saw, I noticed there’s a large missing space for ID 0.15mm, with no jewels available for OD 1.20mm, 1.30mm, 1.40mm.

If the hole for the jewel in a mainplate was for jewel OD 1.20mm, and the watch was considered high grade, what would the appropriate response be? Would it be better to ream the hole out to the next available jewel OD size 1.50mm, or shaping the pivot size down, so that a jewel with OD 1.20mm, and ID 0.14mm can be used? Is reaming the hole in the mainplate from 1.19mm to 1.49mm, or reshaping the pivot considered more intrusive? Technically, making a new jewel is considered best practice, but the next available jewel size would be  too large to grind down, and I wouldn’t think many customers would be willing to pay for the work to make a custom jewel outside of museum grade watches.

Edited May 25, 2022 by ifibrin

[nickelsilver]

2 hours ago, ifibrin said:

Wow, you have access to tools, and have skills most of us can never hope to achieve in our lifetime. Would you be ok sharing how you managed to make this your career path? You can ignore this if it’s too personal.

Anyway, in the Bergeon catalogue I saw, I noticed there’s a large missing space for ID 0.15mm, with no jewels available for OD 1.20mm, 1.30mm, 1.40mm.

If the hole for the jewel in a mainplate was for jewel OD 1.20mm, and the watch was considered high grade, what would the appropriate response be? Would it be better to ream the hole out to the next available jewel OD size 1.50mm, or shaping the pivot size down, so that a jewel with OD 1.20mm, and ID 0.14mm can be used? Is reaming the hole in the mainplate from 1.19mm to 1.49mm, or reshaping the pivot considered more intrusive? Technically, making a new jewel is considered best practice, but the next available jewel size would be  too large to grind down, and I wouldn’t think many customers would be willing to pay for the work to make a custom jewel outside of museum grade watches.

I got into watchmaking accidentally while working (putting off university) while my wife went to school, just met a jeweler my age (early 20s) who was really into watches, especially independent watchmakers, and a year later I was in school. Then straight into a Swiss school, WOSTEP, then taught for a few years, then moved to Switzerland and that was more than 2 decades ago!

 

It always depends on the piece. But in general I'd rather modify something like a pivot than a bridge or mainplate, as, even if there are parts restrictions like crazy, it's more likely down the road someone could put an original jewel and wheel in, but not necessarily replace the mainplate or bridge (to get it fully original). But in the end, if the work is done cleanly and carefully, I bet even a factory watchmaker would miss that a larger jewel had been implemented in a past repair.

 

Yes, fully handmade jewels are expensive. I figure about a day for something like the above marine chronometer jewel. Pictured below with the original, which was cracked.

 

[ifibrin]

1 hour ago, nickelsilver said:

It always depends on the piece. But in general I'd rather modify something like a pivot than a bridge or mainplate, as, even if there are parts restrictions like crazy, it's more likely down the road someone could put an original jewel and wheel in, but not necessarily replace the mainplate or bridge (to get it fully original). But in the end, if the work is done cleanly and carefully, I bet even a factory watchmaker would miss that a larger jewel had been implemented in a past repair.

I would imagine polishing a pivot down to size by 0.01mm diameter is a lot easier than grinding a jewel smaller, or making an entirely new jewel.

In the event you do decide to ream the hole, is there any guideline/ good practice on just how much you should ream a hole for a jewel by? Like say only 0.1mm, example being a 1.09mm hole to 1.19mm? Or is it up to the watchmakers discretion over how he imagines the finished work will look with a larger hole for the jewel.

 

1 hour ago, nickelsilver said:

 

That’s a beautifully made jewel. Is there any reason why the original is clear and not red? Do you have a ready stock of different coloured watch jewel discs which you grind to size and shape?

Edited May 25, 2022 by ifibrin

[nickelsilver]

11 minutes ago, ifibrin said:

I would imagine polishing a pivot down to size by 0.01mm diameter is a lot easier than grinding a jewel smaller, or making an entirely new jewel.

In the event you do decide to ream the hole, is there any guideline/ good practice on just how much you should ream a hole for a jewel by? Like say only 0.1mm, example being a 1.09mm hole to 1.19mm? Or is it up to the watchmakers discretion over how he imagines the finished work will look with a larger hole for the jewel.

 

That’s a beautifully made jewel. Is there any reason why the original is clear and not red? Do you have a ready stock of different coloured watch jewel discs which you grind to size and shape?

Personally, if it needs more than 0.1mm I will open it in a faceplate in the lathe, as I know that I won't lose the position- in fact, if I'm not pressed for time I will often do that even if just 0.1mm, especially on ultra thin watches where the slightest error not only changes the depthing of the gearing but will have wheel rubbing on other parts. I know other watchmakers who don't mind doing more- and it depends one for which component- if for a barrel in a 13"' watch that's a lot different than for an escape wheel in a 7 "' watch if things drift.

 

I have some raw synthetic red ruby, and some red ruby jewel blanks. That's about it. For this one since the original was clear, I used a sapphire crystal as my stock. I don't know why they decided to use clear sapphire instead of red or pink ruby; the piece was made right around the time Verneuil established commercial level synthetic ruby production, so probably not quite available (even if it was a chronometer maker would probably be too cautious to use something so new). I am guessing that red ruby large enough for these jewels was more valuable as a gem, so they went with clear, but really just a guess.

[clockboy]

This excellent vid by Mark show fitting a jewel (balance) and he also covers that the jewel available is not exact so reams out to fit the new jewel.

 

 

[ifibrin]

14 minutes ago, clockboy said:

This excellent vid by Mark show fitting a jewel (balance) and he also covers that the jewel available is not exact so reams out to fit the new jewel.

 

 

Thanks! I have watched that video multiple times but I was wondering  more about the practicalities over when it’s appropriate/inappropriate to ream out a hole… especially if the hole dimension changes substantially if the right size jewel can’t be found.

I’ve also read about how some people face the problem over the hole drifting during reaming, or getting reamed too big (especially over at the NAWCC forums), so I wanted to find out as much as possible over the whole process, as well as alternatives.