Jewels act like the roller bearings or bushings of a watch's internals which are used to combat friction. Friction not only reduces the lifespan of the parts rubbing against each other, it affects accuracy as well. Since jewels were intended to be used on high wear points it made sense that the harder & smoother the material that they are made of, the better the reduction of friction. In 1704 the Swiss astronomer and optician Nicolas Fatio de Duillier patented a way of drilling rubies so they could be used in watch movements. The French company De Beaufré used his technique to manufacture the first watch that incorprated rubies into its mechanism. De Beaufré pocket watch from 1720: These gems were chosen because they consist of one of the hardest elements known to man and can be polished to an extremely sleek finish. They are also not adversely affected by temperature changes which would make other materials expand or contract and therefore alter tolerances. An added bonus to hardness is a longer lifespan. Both rubies and sapphires are the same element: corundum (crystalline aluminum oxide / Al2O3). Originally they were only naturally occurring and had to be mined, then cut with a diamond powder-coated lathe. Jewels also varied in quality. Lower to mid priced movements even used "seconds" - gems that would not pass visual inspection in regular jewelry because they had too many flaws. High end movements have top tier quality jewels mounted in "chatons" (gold cups) that are secured to the metal baseplate of the movement and then burnished. Lower level movement makers simply drilled the hole and attached the jewel directly to the metal. 1966 Longines caliber 370 with jewels in chatons: Interestingly enough, it's the impurities that give rubies and sapphires their color. The higher the content of other elements, the deeper the color. Chromium makes rubies red, and vanadium will give them a purple hue. Titanium and iron give sapphire a blue tint - the higher the iron content, the more yellowish green the color. Pure corundum is clear. In 1892 Auguste Verneuil discovered a process to manufacture synthetic gemstones. He published a paper on the making of synthetic rubies in 1902 which noted that the imitation substance surpassed it's naturally occurring counterpart for industrial uses. Besides being less expensive, the man-made version was practically free from defects and was of a greater purity. Before rubies could be synthesized, only the most costly watches had more than 7 jewels. After that time, it became a marketing game of who had the most since the general public was not aware of the lower price of synthetic gems. Waltham once made a 100 jewel watch! 83 of the rubies were totally useless; the other 17 were in standard functional positions. rotor of the 100j Waltham: photo by Paul Delury There were no regulations on jewels until 1965 when the NIHS (Normes de l'Industrie Horlogie Suisse) stepped in to police the advertising. In 1974 they ruled that all jewels should be rubies. Up until this standard was enacted there were many different grades of materials used (even glass!). The NIHS also defined what functioning and non-functioning jewels are in ISO 1112. The former is a "jewel which serves to stabilize friction and to reduce the wear rate of contacting surfaces of the components of a timekeeping instrument". Of course the latter is any jewel not used for this purpose. As with most laws there are loopholes. Some manufacturers add jewels where they do have a tiny function but are practically useless and don't improve accuracy, reduce much friction or add to the life expectancy of the unit.
Random trivia: nobody knows who invented the flame fusion process for producing synthetic rubies, because the inventor used the process to scam ruby buyers in Geneva and was never caught. cite
Exactly the kind of contribution post I (we) love to see! A friend and I were just discussing moderation and contribution. If your post contributes nothing, don't post it! If you start no shit, there'll be no shit! If you can focus on content and not on trolls measuring their jollies, this forum is indeed a jewel (man-made)!! I'm making almost every sentence a new paragraph to avoid the grammar police. Good post, Dennis!
But then n00bs would never get a high enough post count to sell watches. Hey now, starting shit is fun sometimes!
Thanks! Mechanical Watches for Dummies written by a Watch Dummy. A grasp of how & why helps understand the hobby better.
If you really want to see details of how jewels are made (or at least were in the 1940's) then there's no better than this video... https://archive.org/details/JewelBearings Long and very detailed, but will take you through all the steps in making watch jewels. I doubt things have changed much in terms of techniques today.
Nice post Dennis. Does a chaton have any function besides decoration? Always wondered this. Theory one: the gold is softer metal and cradles the brittle gem or deforms easily to receive the gem. Theory two. The chaton serves as an inert barrier to prevent to ruby reacting with the alloy of the plate. This doesn’t make sense because we see movements without chatons.
Yes. Both theories are bogus. The real reason is for easier replacement of jewels and better centering. The centering is pretty obvious but for the easier replacement of jewels, if you have ever replaced a bezel set jewel (a.k.a. "rubbed in jewel") you will immediately see the benefit of the chaton.
For someone that isn’t a watchmaker (me) I would need more experience to understand your statement or more explanation, which would be appreciated if you care to elaborate. Edit: the ease of replacement makes sense especially with the screwed in type.
There are three common methods for attaching plate jewels to a movement main plate of bridge. The most commonly used system now is friction fitted, where the jewel is pressed into the hole in the plate or bridge with a slight interference fit. Then there's the chaton, where often the chaton will have screws that hold the chaton in the plate or bridge - sometimes the chaton can be friction fit into the plate. The third is bezel set, and as the name suggests is like setting a cabochon stone of some kind in jewelry by holding it in place using a bezel rather than a claw style setting. The bezel is typically created by drilling a hole in the plate, and then forming a bezel from the material around that hole. A cutting tool is used to cut a portion of the plate and fold it back. The jewel is then set into the recess created, and the metal that was folded back is now burnished over the jewel to hold it in place. This is what a bezel set jewel looks like: If you look closely, you can see that the material of the actual plate has been formed over the edge of the jewel to hold it in place. If you are replacing a cracked jewel like this one, you press the jewel out from the opposite side of the bezel, and this fold the bezel back - there are special tools used to clean up the space or make the gap under the bezel bigger. Then the new jewel is set in place, and a special burnishing tool is used to form the bezel back down on the jewel to hold it firmly. One key problem with this is that these jewels are very different in terms of shape than modern jewels, and they haven't been made in 50+ years, so finding jewels of this type that have the right thickness, inside and outside diameters, is increasingly difficult. Sometimes steps have to be taken to thin out a jewel, or reduce it's diameter. The jewel in cross section is shaped more like a football (US) than a friction fitted jewel is. Thick in the middle and then thinner at the outer diameter. These are very common in vintage pocket watches, and collectors of those watches don't want friction fitted jewels installed typically, and they even want the jewels to match in colour. Back when these were made the colouring varied a lot, so some are nearly colourless, some with just a slight shade of pink, and then all the way to ruby red. It's one main reason why I no longer take in pocket watches like this for servicing - the jewels are just too difficult to find. If I take one in it's usually under the condition that if I open it up and find cracked or broken jewels, I refuse the service. But cracked jewels are so common that it seems 90% of the time there will be damaged jewels... The second difficulty of this sort of installation is that you are actually forming and burnishing a part of the movement plate in this case, so if the material work hardens, something breaks off, you are pretty much screwed. There's a reason this system was abandoned a very long time ago. Cheers, Al
The horology 101 series should be put in the stickies section. As UncleBuck has said these type of post are what make the forum a wonderful resource and interesting place to come to. Thank you for taking the time to post this series.
