Why are there jewels in mechanical watches?

Mechanical watches always have the number of jewels they contain written on the calibre. Why are jewels important to mechanical watches and how do they enhance their accuracy? Find out now !

Mechanical watches are made out of metal components. Those components need to move and slide between each other to deliver the main spring’s energy to the watch and eventually to give time! The gearwheels and pivots are therefore submitted to different frictions that wear out components. To prevent components to damage themselves AND to reduce frictions on each other, jewels were selected and particularly rubies.

Jewels in mechanical watches

Rubies indeed have two main characteristics extremely useful for watchmakers as 1) they can be made on demand with the shape/size needed and 2) they are hard enough to last decades.
Thanks to those properties, jewels (we will call rubies like this) are used to separate moving metal parts from other. Jewels become the joint between them and provide excellent sliding functions.

Jewel’s properties are helping watchmakers to respond to their fundamental goal of reducing frictions. By using jewels, calibres become more reliable and accurate. And as you know it, getting the most precise watch has always been the grail of watchmakers. Nowadays, jewels are used in almost all mechanical watches and nothing better has been found to replace them. Watchmakers now try to ameliorate metal components such as the balance spring and anchor escapement to reduce the risks of friction and magnetism… BTW, if you haven’t measured your watch accuracy on Toolwatch.io yet, you should do it by now 😉 Knowing the accuracy is fundamental to better understand our timepieces.

The @montblanc Rieussec chronograph houses a well looking calibre! How do you like the finishing?! #calibre #decorations

A photo posted by Toolwatch ⌚️ (@toolwatchapp) on

To go further in the details: usually there are 4 types of jewels (a. hole, b. hole and cap, c. pallet and d. roller jewels) which correspond to 4 different components (escapement and balance functions, gear trains, center wheels, escapements and balance functions). You will find illustrations of each of them below:


You might wonder what is the yellow spot referring to on the two first illustrations. It is actually oil! To better enhance rubies’ function, oil is used within the jewels. Oil drops are helping the rotation of pivots to reduce frictions. This is also the reason why regularly servicing your watch is important for your calibre. Oil can dry if you don’t use your watch for a while! Recurrent measures of your accuracy will help you determine if your calibre is still working properly or not.

One last thing! Did you know that the more the watch has jewels, the more expensive it is?
This sentence is usually used for marketing purpose. However you should be aware that while the jewels don’t create the value, it still means that the watch might have more functions and therefore might be more expensive.


See you soon for a next article to share our love for mechanical watches ! Do not hesitate to tell us in the comments which article you would like us to write about !