When discussing the craftsmanship behind fine mechanical watches, one term often mentioned is "watch jewels." Despite their name, these tiny synthetic gemstones are not just decorative but serve a crucial functional role in ensuring the smooth operation of a timepiece. Understanding watch jewels can help collectors and enthusiasts appreciate the intricacy of mechanical movements and the evolution of horology.
The History of Watch Jewels
The use of jewels in watches dates back to the late 17th century. In 1704, Swiss watchmaker Nicolas Fatio de Duillier, along with two partners, first introduced the concept of using gemstones to reduce friction in watch movements. Initially, natural gemstones like diamonds, sapphires, rubies, and garnets were used due to their hardness and durability. However, these materials were costly and difficult to work with, reserved for elite pocket watches.
The 19th-century Industrial Revolution changed everything. As mass production demanded durable, precise movements, Swiss brands like Patek Philippe and Vacheron Constantin began integrating synthetic rubies (developed via the Verneuil process in 1902) into their calibers. Synthetic rubies provided the same durability and low friction properties as natural gemstones but were significantly more affordable and easier to produce in large quantities. By the 1920s, even affordable wristwatches boasted 7-15 jewels, transforming them from luxuries into reliable tools. Today, nearly all watch jewels are made from synthetic corundum (ruby or sapphire) due to their exceptional hardness and wear resistance.
The Purpose of Watch Jewels
In a mechanical watch movement, jewels serve several essential purposes:
1. Reducing Friction
Mechanical watches contain numerous moving parts, and friction between these components can cause wear and reduce accuracy over time. Watch jewels, made from synthetic ruby or sapphire, provide a smooth, low-friction surface for these parts to rotate against, ensuring consistent performance.
2. Increasing Durability
By reducing metal-to-metal contact, jewels help minimize wear and tear, significantly extending the lifespan of a watch movement. This is particularly important for high-precision components like the escapement, balance wheel, and gears.
3. Enhancing Accuracy
Friction and uneven wear can cause variations in timekeeping. By stabilizing critical moving parts, jewels contribute to the watch’s precision, helping it maintain accurate time over extended periods.
4. Providing Shock Resistance
Some jewels are used in conjunction with shock-absorbing mechanisms to protect delicate parts, such as the balance wheel pivots, from sudden impacts. The most famous of these systems is the Incabloc shock protection, which incorporates a sprung jewel setting that absorbs shocks and prevents damage.
Types of Watch Jewels
Different types of jewels serve specific functions within a watch movement. Below are the most common types:
1. Hole Jewels
Hole jewels are the most commonly used type, typically found at the pivot points of gears and wheels. These small, disc-shaped jewels have a precisely drilled hole through which an axle passes. The jewel provides a smooth bearing surface, reducing friction and allowing the axle to rotate freely.
2. Cap Jewels
Cap jewels work in conjunction with hole jewels to enhance precision and reduce end-shake (axial movement). Positioned above the hole jewel, cap jewels create a smoother pivot surface for high-speed components like the balance wheel, improving stability and accuracy.
3. Pallet Jewels
Pallet jewels are rectangular or triangular jewels mounted on the pallet fork of the escapement. These jewels interact with the escape wheel, ensuring controlled energy transfer from the mainspring to the balance wheel. By reducing friction at this crucial point, pallet jewels play a key role in the efficient operation of a mechanical movement.
4. Roller Jewels
The roller jewel, also known as an impulse jewel, is a small, cylindrical ruby attached to the roller table of the balance wheel. It interacts with the pallet fork, transferring energy to keep the balance wheel oscillating consistently.
5. Endstone Jewels
Endstone jewels are similar to cap jewels but are primarily used in high-end watches to minimize friction in the escapement. These jewels are often seen in tourbillon movements, where precision and efficiency are paramount.
How Many Jewels Does a Watch Need?
The number of jewels in a watch movement varies depending on its complexity. Below are some common jewel counts and their significance:
7 Jewels: Found in basic, entry-level mechanical watches, covering only essential pivot points.
15-17 Jewels: Considered a "fully jeweled" movement, covering all key friction points in a standard manual or automatic movement.
21-23 Jewels: Common in high-quality movements, with additional jewels in the gear train to further reduce friction and improve longevity.
25-30+ Jewels: Typically found in advanced complications such as chronographs, perpetual calendars, and tourbillons, where extra jewels optimize performance and durability.
Are More Jewels Always Better?
While a higher jewel count can indicate a more sophisticated movement, it is not necessarily an indicator of superior quality. Some manufacturers add "extra" jewels that serve little functional purpose to inflate the perceived value of a watch. In reality, a well-engineered 17- to 23-jewel movement can perform just as well as one with 30 or more jewels, depending on the design and craftsmanship.
