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 4 hours ago 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?