Jewel dimensions…

[tmac1956]

All:

I’m trying to restore an Elgin 16s Model 573 that has a busted balance staff and cracked upper/lower balance jewels. I was able to use a pin gauge to get the following hole dimensions (plus set) with a finger tight fit using the 0.051 pin. So what exactly does that mean? Is it that since it’s a plus set, I need to go down to 0.050 or up to 0.052?

Another question is… does anyone know the pivot dimension or hole jewel dimension for the top and bottom pivot? I attempted to use a digital caliper to measure the new balance staff pivots under the microscope but I just don’t trust the readings I’m getting. I wish I had a Sietz jewel plate to get the measurement, but those things are pricey. If I can get the pivot dimensions I can decide on the correct hole size (I think the Chicago School of Watchmaking recommends that you add .01mm to get the hole size).

Final question… do I need to break down and buy a jewel plate, or is there something else I should be looking at? I know I’m going to be replacing friction fit jewels regularly.

Thanks in advance!
Tom

[david pierce]

Tom,
Pin gauges should be used in pairs. You need to find the largest size pin gauge that will go through the hole and the smallest size gauge that will not. The actual hole size, by default, will be between these two sizes. To increase the accuracy of your measurement, pin gauge sets (VERMONT) are produced in over and under sizes. This will be +.0001″ and
-.0001″ for each given pin diameter.
david

[tmac1956]

@david pierce wrote:

Tom,
Pin gauges should be used in pairs. You need to find the largest size pin gauge that will go through the hole and the smallest size gauge that will not. The actual hole size, by default, will be between these two sizes. To increase the accuracy of your measurement, pin gauge sets (VERMONT) are produced in over and under sizes. This will be +.0001″ and
-.0001″ for each given pin diameter.
david

David:

I have a plus and a minus set. So if I understand you correctly, I use the plus set to find the largest that will go through and find the smallest pin from the minus set that will not. Then take the mean bewteen the sizes for the actual size?

How do you measure a jewel hole? What I would like to be able to do is to measure the size of the pivots, add 0.01mm to those dimensions and that will be the hole size. I just can’t seem to ge a consistent reading under the microscope. I put the balance into a small hole in a bench block to hold it, and tried to measure it with my digital caliper. However, it moves around a little so my readings vary. Plus… I’m afraid if I do this very many times, I’ll score, bend, or even break one.

Any thoughts?

Thanks!
Tom

[david pierce]

Tom,
Lets assume that the desired hole is .051. You pull out .050 -.0001 from the under size set and you pull out .050 from the over size set. Both gauges go through the hole so you put them back into the box an pull out .051 -.0001 and .051 +.0001. You find that .051 -.0001 will pass through the hole but .051 +.0001 will not. You now know that the hole diameter is under .0511″ and over .0509″. This will not necessarily be the arithmatic mean but if the specified part dimension is .051 + or – .0001, then you know that you are within that tolerance.
For the shaft (pivot) diameter if you have a dial indicator that is marked in .0001 inches or .01 mm, lay the pivot on a flat precision surface and measure it with a dial indicator.
david

[tmac1956]

David:

I learn something from you guys everytime I ask a dumb question. I’ll give that a try.

Thanks!
Tom

[Bob Tascione]

Hi Tom,
That model calls for a 6167 staff which would be size 11 pivot. Be aware that this dia. can vary a bit between staffs. I measured a few that I have here and diameters ranged between .104mm to .109mm. I would think that the .01mm clearance for the jewel is in the ball park.
Hope this helps,
Bob

[tmac1956]

Bob:

The 10 mm was one of the numbers that I came up with – as well as about 10 others. So how do you determine the jewel size needed…. are you using a chart for the pivot diameter, do you use a micrometer, or do you have a jewel plate? Just curious.

Thanks for the data!!!!!
Tom

[Bob Tascione]

Hi Tom,
A mic is very helpful if you have no other way to determine the pivot size. Also if you would like to make the following gauges do grab a mic. If all you have is a mic in Inches you can always convert to Metric if you wish.

Many of the old assortments had staffs and jewels categorized by Make, size grade/model number. You could choose the staff from one bottle and a jewel from another. That made it real simple. These assortments are getting harder to find now and when they show up they seem to be commanding pretty hefty prices. Another way is to just use (as you mention above) jewel plates and or simple hole gauges. You would just take the staff and find a jewel that the pivot just fit in to. If it is loose enough and the smaller jewel before it is too small then you could determine what hole size would be best by grabbing a jewel with the same or slightly smaller or larger (depends on the gauge jewel clearance) hole as the gauge jewel. If you lack gauges then you can always go the gauge pin route. If you already have the jewel gauges then you’re all set but if not you can either make a simple set by turning a number of pivots on some steel rods to use as go/no-go pins or as many use to do in the past, just use old broken balance staffs. Simple gauges can be made by inserting the broken end of a balance staff into the end of a small diameter wood dowel and then mark the pivot diameter on the dowel. Doesn’t take long to make a complete set if you have some old staffs laying around. If you have a cheap assortment of jewels laying around you can use them to make a quick gauge by drilling and inserting them into a piece of wood or brass plate, marking their hole sizes for future use. If you’re using bulk assorted jewels and don’t know the hole diameters then the pin gauge is the way to go. There are other types of gauges out there too but thought I would point out a few simple ways to go about it.
Hope this helps Tom,
Bob

[tmac1956]

Bob:

Thanks – that helps a lot!

Tom

[chris mabbott]

Hey Tom,

I have the same problem, I picked up a couple of jewel sets but the jewels/bottles were all mixed up. Once I find the new staff, I pour a few jewels into a dish and find the correct OD first, the I try them on the pivot. It actually sounds like a long process, but usually takes me about 15 mins to go through a couple of hundred jewels 😆 I always seem to get lucky. You can usually judge pretty well once the jewel is sitting on the pivot.

Are you doing rubbed-in or friction?

[tmac1956]

Chris:

These are friction fit. I have yet to be successful at doing a decent rubbed-in job and ultimately windup making a jewel bushing and friction fitting that into the watch using a smaller jewel.

When you are doing your process of placing the balance staff pivot into a jewel, are you looking at a side shake < 5 deg. to deduce a good fit? That sounds like a pretty good method. I have some jewels on hand and I have some more coming, so I think I'll give your method a try.

The pin gauge seems like a good way as well, but my sets only go as small as +-0.011″. However I can buy single guitar strings (for about $0.75 each) that will take me down to 0.007″ in increments of 0.001″. How to get smaller than that? I don’t know.

And now for something completely different (well not COMPLETELY different)

I have a humble request…

I anyone has any pictures of the process of doing a rubbed-in replacement, I would be forever grateful if you could find the time to post them. Or, if you have a job coming up that you wouldn’t mind documenting that would be superb too. David Pierce recommended an old book available in reprint at LuLu (but I can’t remember the title) which indicates that the best way to do this is to break the cracked jewel up and then remove it in pieces, thereby leaving the metal used to hold the jewel intact for the new jewel. I’ve been through the Chicago School of Watchmaking section on this, but it looks a little thin for rubbed-in jewels.

Thanks!
Tom

[chris mabbott]

Tom, would i happen to be hearing a Monty Python influenced phrase in your last post somewhere 😆

I feel your pain my brother, because I was in the same boat, lots of explanations about performing rubbed-in jewel replacement but a complete lack of photographic, step by step instructions.
I’m also guilty of forgetting to take pics, most of the time I’m concentrating on NOT messing up, so I forget. I’m still finding my way around these and formulating my own method.
But the next time I change a rubbed-in, which will be very soon as I have a few broken plate jewels, I will take pics..

I think, jewel/pivot sizing wise, that I have a good eye, which is true, I have one good eye and one not so good 😆
Seriously, the +/_ .01 is the rule of thumb/spec but you can easily determine the correct fit by eye and 12x loupe. it’s like a GO, NO-GO gauge, you can just feel it.
All things being fair, these guidelines apply to the new installation, and if I had all of the correct jewels, a numbered kit with matching numbered replacement staffs, then I could follow these rules, no problem. But I don’t.
I, like most, have had to piece together over time my stock of parts which are not in order and far from organized. I have bags of jewels, some friction most not. So with this in mind, I find the quickest, most accurate way that works for me, because I used to spend hours, days, going through jewels.

It’s like seasoned machinist who just know the angle of their tool bits, so they don’t have to keep pulling out the protractor for every single sharpening procedure.

My goal, get the OD first, then worry about the hole size, so I can zip through 200 hundred jewels with my mic in no time, I put them aside, then I look at the pivot hole size, for me it works.
I really don’t like to change the design of a watch, although in desperation, I have, replacing RI with Seitz, but those RI jewels were a crux for me and I really wanted to get it learned 😆

Do you have a set of the hole opening/closing tools Tom?

[chris mabbott]

Tom, I had some links I found for RI jewels, as you say, really, very few with photos, but the poster has removed the images so now the thread is pretty useless.

But I did come across this one which I had saved & has helped me with many 7 jeweled watches where the holes are always worn..

http://people.timezone.com/library/workbench/workbench631678823983930377

[tmac1956]

@Chris Mabbott wrote:

Tom, would i happen to be hearing a Monty Python influenced phrase in your last post somewhere 😆

I feel your pain my brother, because I was in the same boat, lots of explanations about performing rubbed-in jewel replacement but a complete lack of photographic, step by step instructions.
I’m also guilty of forgetting to take pics, most of the time I’m concentrating on NOT messing up, so I forget. I’m still finding my way around these and formulating my own method.
But the next time I change a rubbed-in, which will be very soon as I have a few broken plate jewels, I will take pics..

I think, jewel/pivot sizing wise, that I have a good eye, which is true, I have one good eye and one not so good 😆
Seriously, the +/_ .01 is the rule of thumb/spec but you can easily determine the correct fit by eye and 12x loupe. it’s like a GO, NO-GO gauge, you can just feel it.
All things being fair, these guidelines apply to the new installation, and if I had all of the correct jewels, a numbered kit with matching numbered replacement staffs, then I could follow these rules, no problem. But I don’t.
I, like most, have had to piece together over time my stock of parts which are not in order and far from organized. I have bags of jewels, some friction most not. So with this in mind, I find the quickest, most accurate way that works for me, because I used to spend hours, days, going through jewels.

It’s like seasoned machinist who just know the angle of their tool bits, so they don’t have to keep pulling out the protractor for every single sharpening procedure.

My goal, get the OD first, then worry about the hole size, so I can zip through 200 hundred jewels with my mic in no time, I put them aside, then I look at the pivot hole size, for me it works.
I really don’t like to change the design of a watch, although in desperation, I have, replacing RI with Seitz, but those RI jewels were a crux for me and I really wanted to get it learned 😆

Do you have a set of the hole opening/closing tools Tom?

Yes – I’ve bought several sets. Knowing how to use them on the other hand….

Thanks!
Tom

“What have the Romans ever given us? ” MP

[tmac1956]

@Chris Mabbott wrote:

Tom, I had some links I found for RI jewels, as you say, really, very few with photos, but the poster has removed the images so now the thread is pretty useless.

But I did come across this one which I had saved & has helped me with many 7 jeweled watches where the holes are always worn..

http://people.timezone.com/library/workbench/workbench631678823983930377

Chris:

That’s a great link. I’ve snagged it for future reference.

Thanks again!
Tom

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