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Looking for correct jewel size for Illinois Bunn Special

Max50916
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Max50916 Watch Enthusiast

Max50916

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Hello, I'm looking for the correct jewel for the lower balance. It's a 16s movement Bunn Special (14th model) but I'm having a hard time determining the correct hole size. The one currently in there has a big crack and needs replacement. Does anyone know any resources which would tell me which pocket watch models used which hole size etc? I don't have a hole gauge, so haven't been able to try that out. Thank you!

PXL_20220808_152940279.jpg

PXL_20220808_153315014.jpg

mikepilk Distinguished Member

mikepilk

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Had a look in Marshall and Swigart but couldn't find the size. In Swigart in says that pivots come in various sizes - which is my experience of these types of watch.  Unless you can measure the pivot very carefully with a micrometer - though it's not recommended. A better way would be to find something (old pivot?) that fits the top balance jewel correctly, and measure that.

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JohnR725 Distinguished Member

JohnR725

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2 hours ago, Max50916 said:

The one currently in there has a big crack and needs replacement.

If you look at the big crack does the crack go all the way to the center hole? Has it damaged the center hole? If you look at the balance staff is the pivot scored from the result of running in a cracked Jewel?

In vintage pocket watches you will find flaws and things that look like cracks. But if you look at the hole itself it looks smooth and shiny it's not a problem. 

1 hour ago, mikepilk said:

pivots come in various sizes

Yes pocket watch staffs typically come in several sizes of pivots for the exact same staff number. Then of course the balance hole jewels will do the same thing. Which means you usually stuck having to measure something you can't just look up and find the exact one your watch Is using. Then of course there was also the problem of variations over time because of manufacturing changes.

2 hours ago, Max50916 said:

Does anyone know any resources which would tell me which pocket watch models used which hole size etc?

That's more of a modern watch repair question. In the case of this watch the Jewel settings will only fit other Illinois watches. It be nice if you give us the size of the jewel setting that would speed things up considerably. I have a link to a pocket watch database if you like is sometimes a give you parts listings but not today this one is a listed.

Then snipped out an image from the 1923 parts catalog problem is it's 1923 new watches made after that so it's not listed at all. I sub another image of another reference book and basically you're still stuck with you have to measure the jewel setting to see which one it is. Then you have to measure the balance pivots to see which hole size you need. Because as far as I know there was never a listing of the exact part that your watch would need.

https://pocketwatchdatabase.com/search/result/illinois/5152334

 

Illinois balance jewel setting.JPG

Illinois 1923 parts book balance jewel lower.JPG

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Max50916 Watch Enthusiast

Max50916

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3 hours ago, JohnR725 said:

If you look at the big crack does the crack go all the way to the center hole? Has it damaged the center hole? If you look at the balance staff is the pivot scored from the result of running in a cracked Jewel?

In vintage pocket watches you will find flaws and things that look like cracks. But if you look at the hole itself it looks smooth and shiny it's not a problem. 

Yes pocket watch staffs typically come in several sizes of pivots for the exact same staff number. Then of course the balance hole jewels will do the same thing. Which means you usually stuck having to measure something you can't just look up and find the exact one your watch Is using. Then of course there was also the problem of variations over time because of manufacturing changes.

That's more of a modern watch repair question. In the case of this watch the Jewel settings will only fit other Illinois watches. It be nice if you give us the size of the jewel setting that would speed things up considerably. I have a link to a pocket watch database if you like is sometimes a give you parts listings but not today this one is a listed.

Then snipped out an image from the 1923 parts catalog problem is it's 1923 new watches made after that so it's not listed at all. I sub another image of another reference book and basically you're still stuck with you have to measure the jewel setting to see which one it is. Then you have to measure the balance pivots to see which hole size you need. Because as far as I know there was never a listing of the exact part that your watch would need.

https://pocketwatchdatabase.com/search/result/illinois/5152334

 

Illinois balance jewel setting.JPG

Illinois 1923 parts book balance jewel lower.JPG

Wow lots of good information to take in here, thank you! I'll need to try and measure the jewel size soon.

 

The crack is on the hole, so it's almost shaped like a tear drop, so it definitely needs to be replaced.

 

Thank you very much for all the info!

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