What is too much wear in a jewel hole ?

[mikepilk]

1 hour ago, VWatchie said:

Interesting question and now that you mention it I don't think I've ever heard anyone mention jewel-bearing wear. Yes, cap jewels for sure and I've seen it several times (the famous dimple). I'm not sure, and I could be imagining, but I think I've seen jewel holes slightly oval-shaped. Could that be a worn hole? 

I've seen oval shaped holes too. So unless it's a manufacturing defect, it must be wear of the jewel.

[Nucejoe]

1 hour ago, VWatchie said:

What I've done when I've seen excessive side shake is burnish the pivot (slightly Coca-Cola bottle-shaped pivot) and replace the jewel.

See          Coca-Cola has found its way into watch repair, more than we give it credit for. 

 

 

 

[nickelsilver]

I remember reading about carbide formation in steel during heat treatment; it's a normal part of the process. The article (lost to the internets) mentioned something about the possibility of pocket concentrations of certain carbides or something, and in discussion with folks smarter than I it was suggested that this could be the cause of jewel wear under certain circumstances. I see that silicon carbide has a Mohs hardness of 9-10, so it could wear ruby (Mohs 9), and silicon is a normal alloying element in steel (it's in Sandvik 20AP, the common steel used for turned watch parts). Whether that silicon does form silicon carbide (apparenly "primary silicon carbide" is actually used as a silicon source for steel making), or occasionally does, or occasionally does and forms "pockets" that can wear ruby, is beyond my pay scale.

 

Logically I have to go with Frank on this one. I worked on new production pieces for a well known complications maker some years back, and this caliber was well known for wearing the cap jewels very quickly. The old time watchmakers there told me to always clean the bejesus out of the balance pivots, with dense pegwood, screwing the end of the pegwood (soaked in benzine) down on the pivot a dozen times or so. Just to see, I tried leaving a balance un-pegwooded, and after just a few weeks the cap jewels showed wear, where the treated pivots didn't wear the cap jewels at all. So some kind of contamination with abrasive at the factory level? Would have to be aluminum oxide at least, or diamond.