Understanding Jewels

[EdB]

Greetings all, 

My question pertains to what type of jewel to order in terms of cylindrical or olive. I understand that certain shapes are associated with certain parts. Cap, pallet and balance jewels are not in question, it's the others. I have a cracked pallet fork jewel in the mainplate that I have to repair, but after visiting some suppliers websites I found that their are two choices available. Can someone clarify where to use which pivot hole, and possibly the reasoning behind it. Any information would be appreciated. 

 

Ed... 

[Neverenoughwatches]

4 hours ago, EdB said:

Greetings all, 

My question pertains to what type of jewel to order in terms of cylindrical or olive. I understand that certain shapes are associated with certain parts. Cap, pallet and balance jewels are not in question, it's the others. I have a cracked pallet fork jewel in the mainplate that I have to repair, but after visiting some suppliers websites I found that their are two choices available. Can someone clarify where to use which pivot hole, and possibly the reasoning behind it. Any information would be appreciated. 

 

Ed... 

Hi Ed. I think you are referring to the jewel shape to suit the type of pivot that it is for.  Conical or straight pivot. S/S, C/C , S/C or C/S.  Though this usually is the escape wheel and whether a cap jewel is used. What are the two choices Ed ?

Edited November 28, 2022 by Neverenoughwatches

[nickelsilver]

For hole jewels, there are ones with straight sided holes and ones with olive holes as you have seen. Olive holes have curved hole walls, straight are self explanatory.  Olive hole jewels reduce contact area and thus friction, and are generally used in areas that are most sensitive, like balance/ fork/ escape wheel. They also generally (not always) have a convex face opposite the oil sink. The convex face further reduces friction when used with a shouldered pivot, and when used with a cap jewel (oil sink facing the arbor/staff) promotes capillary attraction of the oil between the jewel face and the cap jewel.

 

Many old high grade watches have convex faces on all the jewels. Some may also have olive hole jewels up to the escape wheel or further. If replacing a jewel, certainly go for olive hole with convex face for a balance, and it's a better choice for other places if the size is available.

Edited November 29, 2022 by nickelsilver

[Neverenoughwatches]

26 minutes ago, Neverenoughwatches said:

Hi Ed. I think you are referring to the jewel shape to suit the type of pivot that it is for.  Conical or straight pivot. S/S, C/C , S/C or C/S.  Though this usually is the escape wheel and whether a cap jewel is used. What are the two choices Ed 

Ah a little research has thrown this up Ed. The olive jewel has a curved inner surface that helps reduce friction compared to a straight hole. I imagine in a verical position this is more effective. I would think hard to tell the difference visually when choosing to replace. Probably used on higher end watches.

Just now, Neverenoughwatches said:

Ah a little research has thrown this up Ed. The olive jewel has a curved inner surface that helps reduce friction compared to a straight hole. I imagine in a verical position this is more effective. I would think hard to tell the difference visually when choosing to replace. Probably used on higher end watches.

Haha scratch that nickelsilver already answered

[EdB]

On 11/28/2022 at 12:15 AM, nickelsilver said:

For hole jewels, there are ones with straight sided holes and ones with olive holes as you have seen. Olive holes have curved hole walls, straight are self explanatory.  Olive hole jewels reduce contact area and thus friction, and are generally used in areas that are most sensitive, like balance/ fork/ escape wheel. They also generally (not always) have a convex face opposite the oil sink. The convex face further reduces friction when used with a shouldered pivot, and when used with a cap jewel (oil sink facing the arbor/staff) promotes capillary attraction of the oil between the jewel face and the cap jewel.

 

Many old high grade watches have convex faces on all the jewels. Some may also have olive hole jewels up to the escape wheel or further. If replacing a jewel, certainly go for olive hole with convex face for a balance, and it's a better choice for other places if the size is available.

Yes! This is the clarification I was looking for. The jewel I have to replace is the escape wheel jewel in the mainplate. I will try to source an olive shaped jewel if the size is available. I had made this assumption but being fairly new to the trade I wanted someone with more experience to chime in. Thanks for your assistance. 

Now the only problem I have is to determine the best way to remove the broken jewel. I do have a jeweling tool so that is not the issue. The issue lies with the mainplate itself. The jewel sits in a recess on the dial side of the movement so setting up the correct stump is a bit perplexing, as this is the side I would prefer to push the jewel out to. As I have much better reference surface on the train side to record base plate depth vs depth of jewel prior to removing which in my head would make replacing a whole lot easier since I would have a depth to install to. 

On 11/27/2022 at 11:38 PM, Neverenoughwatches said:

Hi Ed. I think you are referring to the jewel shape to suit the type of pivot that it is for.  Conical or straight pivot. S/S, C/C , S/C or C/S.  Though this usually is the escape wheel and whether a cap jewel is used. What are the two choices Ed ?

That is correct. I do apologize in advance for not knowing the abbreviations you posted. But I am replacing a jewel for the escape wheel in the mainplate. Movement is a AS ST 50/51.

[Neverenoughwatches]

2 hours ago, EdB said:

Yes! This is the clarification I was looking for. The jewel I have to replace is the escape wheel jewel in the mainplate. I will try to source an olive shaped jewel if the size is available. I had made this assumption but being fairly new to the trade I wanted someone with more experience to chime in. Thanks for your assistance. 

Now the only problem I have is to determine the best way to remove the broken jewel. I do have a jeweling tool so that is not the issue. The issue lies with the mainplate itself. The jewel sits in a recess on the dial side of the movement so setting up the correct stump is a bit perplexing, as this is the side I would prefer to push the jewel out to. As I have much better reference surface on the train side to record base plate depth vs depth of jewel prior to removing which in my head would make replacing a whole lot easier since I would have a depth to install to. 

That is correct. I do apologize in advance for not knowing the abbreviations you posted. But I am replacing a jewel for the escape wheel in the mainplate. Movement is a AS ST 50/51.

The abbreviations here would be for ordering an escape wheel or a lever. Based on their jewel set up. C/S would have a capped jewel on the train side, S/C would be a capped jewel on the dial side, C/C would be capped both sides and S/S would be capped neither side. Not entirely sure if the abbreviations are for capped and standard of the jewel or conical and straight of the pivot. Perhaps Nicklesilver can answer this for us .