If you've ever looked closely at a watch's technical specifications, you've probably noticed a mention of jewels. You might see something like "21-jewel movement" or "17 jewels" listed in the description. But what exactly are these jewels, and why are they important?
Despite sounding luxurious, watch jewels are not about decoration or added value in the way diamonds are. Instead, they're small synthetic rubies or sapphires that play a crucial role inside the movement of a mechanical or automatic watch. In this article, we’ll break down what watch jewels do, where they are used, how they evolved, and how they impact the performance and longevity of a watch.
What Are Watch Jewels?
Watch jewels are tiny pieces of synthetic corundum, usually ruby, that are placed at key pivot points inside a watch movement. They act as bearings for gears and other moving parts, helping to reduce friction and wear.
Because these synthetic jewels are extremely hard and smooth, they provide a low-friction surface that ensures parts can rotate more freely. This helps increase the watch's accuracy and extend the life of its components.
To give you an idea of their hardness, synthetic rubies measure 9 on the Mohs scale-just below diamonds. That’s harder than steel, brass, or even hardened alloys used in watches. This makes them ideal for long-term performance.
Why Use Jewels in Watches?
The primary reasons are:
- Reducing Friction: Metal parts rubbing against each other generate friction and heat. Jewels help to minimize that.
- Increasing Durability: Jewels are harder than metal, so they last longer and protect the movement from wear.
- Improving Accuracy: Less friction means smoother operation, which results in more precise timekeeping.
- Preserving Lubricants: The smooth jewel surfaces help watch oil stay in place and last longer.
Here’s a quirky bit: in older watches, the oil would eventually dry out and leave a green gunk. With jewel bearings, oil stays where it should, making your next service bill a little less painful.
A Brief History of Watch Jewels
The use of jewels in watchmaking dates back to the early 1700s. Nicholas Facio and Peter Debaufre were among the first to experiment with jewels to reduce friction in pocket watches.
In the beginning, natural gemstones were used, often requiring hand-cutting and polishing. This made jeweled watches expensive and rare. But in the early 20th century, Swiss manufacturers began using synthetic rubies, which are chemically identical to natural rubies but much more affordable and consistent in quality.
Synthetic ruby was first created by French chemist Auguste Verneuil in 1902 using a flame-fusion process. This breakthrough made it possible to mass-produce watch jewels with precise tolerances.
By the mid-20th century, virtually all mechanical watches used synthetic jewels, and it became a standard in the industry.
Where Are the Jewels Placed?
Jewels are placed at strategic locations in a movement, mainly where metal parts come into contact and friction is highest. Common jewel positions include:
- Balance Wheel Pivots: The heart of the movement. Jewels reduce friction and allow stable oscillation.
- Escape Wheel and Pallet Fork: These parts are under constant motion and stress.
- Center, Third, and Fourth Wheels: These wheels drive the hands and need stable, low-friction rotation.
Some jewels are also used as capstones or endstones, which help hold lubricants in place and protect the pivots.
Interestingly, even the shock protection system-like Incabloc-uses a pair of cap and hole jewels for the balance staff to reduce damage during impacts.
How Many Jewels Does a Watch Need?
There is no fixed number, but most traditional mechanical watches have between 17 and 23 jewels.
- 17 jewels is considered the standard for a fully jeweled movement, covering all major contact points.
- Additional jewels may be added for complications like automatic winding systems, chronographs, or calendars.
More jewels don’t necessarily mean a better watch. At some point, they provide diminishing returns. In some cases, manufacturers have added jewels purely for marketing.
In technical terms, the minimum number of jewels required for a basic time-only watch is 7, but this would be a bare-bones setup. A "fully jeweled" movement with 17 jewels includes support for the mainspring barrel, gear train, escapement, and balance wheel.
Fun Fact: The Myth of "More Jewels = Better Watch"
In the 1950s and 1960s, some brands started adding excessive jewels (even up to 100 or more) just to attract buyers. These extra jewels were often non-functional. Eventually, watch industry regulations stepped in to prevent misleading advertising.
One particularly infamous model was the "Benrus 100 Jewel" watch. While it did have 100 jewels, most were added in spots where they served no purpose - some were even glued in place!
Types of Watch Jewels
There are a few different types of jewels used in watchmaking:
- Hole Jewels: These are donut-shaped and used for gear axles to pass through.
- Cap Jewels: Flat jewels that sit on top of hole jewels to prevent vertical movement.
- Pallet Jewels: Found on the pallet fork. These interact with the escape wheel.
- Impulse Jewel: Attached to the balance wheel. It receives energy from the pallet fork.
Modern CNC machines can cut these tiny jewels to sub-millimeter tolerances. For reference, the typical hole jewel has a center diameter of around 0.1 to 0.2 mm, and it needs to be absolutely precise for the gear pivots.
Examples of Watch Models and Their Jewels
- Seiko 5 SNK807: This popular entry-level automatic watch has a 21-jewel movement. It covers all the key friction points and is known for its durability.
Seiko 5 SNK807 (21 Jewels) Store Link Ebay Buy on Ebay Amazon Buy on Amazon - Rolex Submariner (Caliber 3235): This high-end dive watch has 31 jewels, which support not just timekeeping but also the date mechanism and automatic rotor.
Rolex Submariner (Caliber 3235) Store Link The Luxury Closet Buy on The Luxury Closet - Hamilton Khaki Field Mechanical: Uses a 17-jewel hand-wound movement. A classic example of a fully jeweled manual watch.
Hamilton Khaki Field Mechanical (17 Jewels) Store Link Ebay Buy on Ebay Amazon Buy on Amazon - Orient Bambino (22 jewels): Elegant automatic dress watch with the in-house F6724 movement. Offers hacking, hand-winding, and excellent jewel integration. A top choice for affordable mechanical timepieces.
Orient Bambino (22 jewels) Store Link Ebay Buy on Ebay Amazon Buy on Amazon
These examples show how jewel count can vary depending on complexity and brand philosophy.
How Jewels Affect Reliability
A watch's reliability depends on how well it handles internal friction and wear. Jewels play a central role in this:
- They reduce wear and tear on pivots and wheels
- They help hold oil in place for longer lubrication life
- They stabilize moving parts, improving accuracy and consistency
Without jewels, watches would require much more frequent servicing and would wear out faster.
Also, jewel placement affects shock resistance. A properly jeweled and protected balance wheel can absorb a surprising amount of abuse - just don't go playing tennis with a vintage dress watch.
Are There Watches Without Jewels?
Yes, but they're usually very low-cost, mass-produced quartz watches. Since these watches have fewer moving parts, they don't need jewels in the same way mechanical watches do.
Some digital watches and electronic timepieces have no jewels at all. But there are exceptions - some high-accuracy quartz movements, like those used in the Seiko 9F series, still include jewels to reduce friction in key areas.
Conclusion
Watch jewels may be small, but they play a big role. They reduce friction, improve accuracy, and make your watch more reliable over time. Whether you're looking at an affordable Seiko or a luxury Rolex, knowing the function of jewels can help you better understand what you’re buying.
And remember: more jewels don’t always mean a better watch. What matters most is how those jewels are used.
If you ever want to impress someone at a party, just mention that your watch uses synthetic corundum pivot bearings and watch their eyes glaze over—or light up, depending on the crowd.
Adding a watch with a solid, well-jewel movement to your collection is a great choice for both beginners and seasoned enthusiasts.