Cap jewel with what looks like a circular engraving around the edge

[Bill2024]

Hi All,

I’ve been cleaning a Tissot 27B-21 movement and the cap jewels on the top and bottom of the balance are different. The bottom jewel is what I’ve seen before, ie perfectly flat and shiny when clean. The top one though looks to have what appears to be a circle near the edge. It definitely won’t clean off and almost looks to be engraved.

Is this just another type of cap jewel that I’ve not seen before or is there a problem with it. 

thanks, Bill

Edited Tuesday at 04:57 PM by Bill2024

[mbwatch]

Yes - that type of jewel does exist and you will encounter it from time to time. I believe the groove cut into it provides an oil barrier, so lubrication cannot flow out away from the pivot.

I have no idea where replacements could be bought if you needed one though.

[mikepilk]

These are quite common. I don't know how that make the groove.  

I always use Fixodrop on the cap jewels to keep the oil in place, so the grooves aren't needed.

[Bill2024]

36 minutes ago, mbwatch said:

Yes - that type of jewel does exist and you will encounter it from time to time. I believe the groove cut into it provides an oil barrier, so lubrication cannot flow out away from the pivot.

I have no idea where replacements could be bought if you needed one though.

Interesting. It also seems strange that it’s only the jewel on the top of the balance that has the grove and not the one on the bottom. I guess maybe one of them got replaced at some point. 

29 minutes ago, mikepilk said:

I always use Fixodrop on the cap jewels to keep the oil in place, so the grooves aren't needed.

I’ve never used Fixodrop but I think it’s something I will look into to. Can I just ask how you use it when oiling the cap jewels?  

[nickelsilver]

14 hours ago, Bill2024 said:

 

I’ve never used Fixodrop but I think it’s something I will look into to. Can I just ask how you use it when oiling the cap jewels?  

I hold the jewel by its outside, dip in Fixodrop, lay it on paper and let it dry. With shock jewels, I then place oil in the center of the cap, and place the hole jewel in setting on top. With normal jewels, I assemble, and oil through the hole jewel.

[mikepilk]

I use Fixodrop on cap jewels, pallet stones and escape wheels.

I just hold the jewels in some Fixodrop for about 30s then let them dry. 

[VWatchie]

On 4/22/2025 at 7:10 PM, mikepilk said:

These are quite common.

I've never seen them, then again, I haven't got a ton of experience, but "common"? Really? In what context have you seen them? I'm not questioning you. I am sincerely curious why I've missed it.

On 4/22/2025 at 7:39 PM, Bill2024 said:

I’ve never used Fixodrop but I think it’s something I will look into to.

An alternative to Fixodrop is to apply less oil (no more than 50 % of the circle area). The only downside would be that it would shorten the service interval. More oil will prolong the service interval, but if the movement is subjected to trauma, there's a risk it will be displaced. Fixodrop makes it more stable. Unfortunately, Fixodrop is seriously expensive.

[caseback]

45 minutes ago, VWatchie said:

I've never seen them, then again, I haven't got a ton of experience, but "common"? Really? In what context have you seen them? I'm not questioning you. I am sincerely curious why I've missed it.

I've seen them on several swiss-made movements as well. Last one was a Tissot if I remember correctly.

[mikepilk]

1 hour ago, VWatchie said:

In what context have you seen them? I

In cap jewels on several watches I have serviced over the years.

I've recently serviced a couple of Longines movements where the cap jewels were colourless. They are a real pain. Without colour they disappear when immersed in any liquid for cleaning 

1 hour ago, VWatchie said:

Fixodrop is seriously expensive.

Not necessarily. Cousins do a 10ml bottle for £26 which will last me for years. That's just half the price of a simple Bergeon silicone cushion, so not too expensive