Chronosect

Dr. N.

The stones are a simple and ingenious solution to the friction problem. In mechanical watches, the rotating parts are inevitably subject to the resistance of the material on which they are hinged. A first solution to the problem can be the use of polished metals to increase their surface hardness and lubrication. But they are palliative: a watch cannot always be lubricated in every area subject to friction, both because it would require continuous revisions, and because too much lubricant attracts dust and it can itself cause dirt if it deteriorates with age.

One possible solution is to use ball bearings. But they are bulky and heavy: it is certainly unthinkable to use them in the smallest gear trains. They are good for the winding rotor, certainly not for the balance wheel.

For their lightness, hardness and - today - inexpensiveness, semiprecious stones represent the ideal choice in the hinges of watch wheels. In this article, we will see how the precious stones are made so much appreciated in the making of mechanical watches, i rubies.

We can see, in this Rolex Daytona Zenith movement, the presence of 31 rubies

Rubies in watchmaking

Traditionally, stones are called “rubies” in watchmaking, due to their color and chemical composition. In reality, it is not natural rubies, but aluminum oxide worked with a complex process to make synthetic rubies. Watchmakers prefer to refer to these stones as "synthetic corundum". A curiosity: the term "corundum" comes from the Sanskrit "kuruvinda", which means "ruby".

Whether you prefer to call it corundum or ruby, the anti-friction red stone is an indispensable component of a mechanical movement: thanks to it, our beloved watches can function while minimizing friction, the number one enemy of every timepiece.

The rubies are clearly visible in this hand-wound chronograph

How are synthetic rubies made?

From bauxite, a naturally occurring mineral, alumina, an aluminum oxide, is obtained. This is baked in the oven at 1200 ° C, to pulverize it. Chromium oxide powder is added to the alumina powder, which gives the finished stone its characteristic reddish color.

A flame at over 2000 ° C melts this mixture of powders, which is then made to solidify on a refractory support containing crystallization germs. These serve to orientate the crystallization of the material in a certain way.

After cooling for several hours, it will finally be possible to harvest the fruit of so much work: corundum, or ruby, synthetic.

How many rubies are there in a watch?

I hand-wound mechanical movements simpler ones usually settle for 17 rubies. We go above 20 for an automatic and we go to grow for watches with a greater number of internal components: the complicated ones, of course, will require a higher number of jewels to reduce internal friction, as they contain more components that rotate.

A Rolex 3235, the heart of the Submariner, with several clearly visible rubies

How to take care of the rubies in my watch?

Watchmaking rubies are not particularly expensive, as we have seen: they are made with industrial synthesis processes. They are to be considered as other parts of the movement. Being harder than the metal that insists on them, they do not need maintenance: they will not wear out.

However, it is important that the watch is serviced by capable and competent watchmakers, to avoid the mistake of lubricating the components that rest on the rubies too much or with too fluid liquids: a balance wheel, for example, needs very little very dense grease, because it rotates very quickly and it is necessary to prevent the grease from dripping and dirtying the parts more sensitive than the barbell itself, like the spiral spring.

We therefore advise you to rely on Chronosect to find a trusted watchmaker that it intervenes correctly in servicing your watch.