Noob question I know but Its not common knowledge to me. Also are they ruby's ?

 

They are synthetic rubies or sapphires, and are used as bearings due to their hardness and long-wearing properties.

 

@gatorcpa had a great series of posts on TZ? Or was it somewhere else on watchmaking 101 which explained it really well. I will hunt for it

Edit: it was watchtalkinfo

 

It was @ulackfocus
http://www.watchtalkforums.info/forums/content.php?r=494-Horology-101-understanding-your-watch

 

Yep, that was me - a watch dummy writing a watches for dummies archive.

Here are the direct links to the two parts about jewels:

http://www.watchtalkforums.info/forums/thread14382.html

http://www.watchtalkforums.info/forums/thread14627.html

Not to be confused with this Jewel:



..... who can be quite a cutie when she's all gussied up:

 

^ ^ ^

Schwing.

 

I like both kinds

 

Cool writeup Dennis. A very belated thanks!

 

Most jewels in a watch are a form of plain bearing - https://en.wikipedia.org/wiki/Plain_bearing

Plain bearings can be made of many materials, and the material used in most watch jewels is corundum (aluminum oxide). Corundum can be different colours depending on what impurities are in them - this is the only difference between a ruby and a sapphire for example - they are both corundum. Natural stones were used at one point, so they were actual mined rubies, but jewels in modern watches are man made versions.

If you really want to dig deeper than most to learn about how man made jewels are produced, then take an hour and 12 minutes and watch this:

Of course things would have changed since the 40's, but it gives you some basics of jewels as well as how they are produced.

Man made jewels have fewer inclusions, so are better quality for bearings than natural stones. Man made jewels go back a long way - on a recent trip to the German watchmaking town of Glashütte, I took this photo of jewels made at the old watchmaking school there - these items are on display in the Glashütte watchmaking museum:



You can see various shades and colours in these jewels - red, pink, blue, yellow, green, and some nearly colourless. Although most jewels you see are red, it's not uncommon still to see various colours of jewels in watches - here is a blue jewel in a Zenith pocket watch:



It was the only blue jewel in the movement actually, which was a bit odd. Here is a pallet fork from a vintage Rolex, and the jewels on the fork are colourless:



Jewels provide a hard wearing surface for the steel pivot to ride on in most cases. The surface wears well, reduces friction, but they can be brittle:



This jewel is in place in an assembled watch, and the pivot of the jewel can be seen:



The jewel is harder that the pivot going through it, so when something wears, it will be the pivot on the wheel usually:







In contrast here is a bushing in a watch made of brass - it serves the same purpose as the jewel, but in this case the bushing wears instead of the pivot that goes through it:



Although jewels are very hard, they can show wear, although not as dramatic as what you see on the pivots:



Here you can see wear on the pallet jewels of this watch from the escape wheel teeth:



They can come in different shapes and sizes for different applications. Jewels can be stepped, have straight holes, or olive holes, and some use cap stones to limit the axial travel of the pivot, so balance jewels have these as well as train jewels in some higher grade watches.

Some vintage high grade American pocket watches use diamond cap jewels, but those are not terribly common.

Hope this helps. If you have any other questions, just ask.

Cheers, Al

 

Why they make your watch look pretty, that's what they do