One of the pieces of information often supplied by watch brands is the number of jewels in a watch. In this article, we will explain what that means, and how it became a part of the standard marketing material.
The jewels in watches are specially shaped rubies which act as bearings to reduce friction and wear in watches (more on that later). While ruby sounds expensive you don’t need to worry about the watchmaker or jeweler stealing the jewels out of your watch. The rubies used in watches are tiny, synthetic, and useless for anything other than bearings in a watch. Replacement jewels cost between $5 and $20.
For 300 years the best watches have had ruby jewels in them to reduce friction. There are several different versions of the history of the use of jewels in watches. At approximately the same time 3 watchmakers developed the use of jeweled bearings in watches. Nicolas Fatio de Duillier patented a method for drilling holes in jewels in 1704 and shortly thereafter, or at about the same time, Peter and Jacob De Beaufre may have made the first watches to incorporate rubies. In 1892 Auguste Verneuil developed a technique for manufacturing synthetic corundum (the mineral composition of rubies and sapphires) and for the last 100 years synthetic corundum has been used almost exclusively.
Ruby (or corundum) is a very hard mineral measuring 9 on the Mohs hardness scale. Only diamonds are harder. This hardness means they will resist wear. Additionally, ruby’s tight crystalline structure means it can be polished to a very smooth surface. This smooth surface when paired with some lubrication and a steel component provides a very low coefficient of friction allowing for a more efficient transfer of energy through the watch. Your watch beats somewhere between 150 and 250 million times per year. All those moving components can really take a beating but the properties of low friction and hardness provided by ruby jewels mean the watch will be able to run with less force and for a longer time period without causing any damage to itself.
Before the use of synthetic ruby, the jewels in watches were cut from natural stones and therefore expensive. Even during the early days of synthetic jewels, the cost of manufacturing and installing jewels in watches was a significant cost in the production of a watch. Ideally nearly every bearing surface would be made from rubies, but in order to keep the cost of watches reasonable, they are installed in the most critical areas. This is why the jewel count became a part of the marketing: the number of jewels was a sign of the quality of the watch.
The modern manual wind wristwatch usually has about 17 Jewels. An automatic watch will have approximately 25 Jewels and complicated watches may have many more. Even some quartz watches have jewels. At the turn of the 20th century, you could buy pocket watches with anywhere from 0 to 25 jewels. Inexpensive “Dollar Watches” usually had no jewels. The most economical jeweled pocket watches had 7 Jewels. A good quality watch had 15 or 17 jewels and high-end watches had between 19 and 23 Jewels. The extra jewels in the watch usually mean that more bearing surfaces are protected from becoming worn and that the total amount of energy lost to friction in the gear train is reduced. The reduction in friction means it easier to deliver a consistent force to the escapement which means better timekeeping.
Wristwatches (and especially automatic wristwatches), had different needs for jewels and before the industry settled on “typical” jewel counts the brands took every opportunity to differentiate themselves using the number of jewels in their watches. For some brands, cost is of no concern, and for others they want you to believe that their watches are better than they really are. In the 1960s the market was flooded with competing watch brands and one way they could distinguish themselves was by producing watches with more jewels. It almost felt like a competition to see who could include the most jewels in a watch. Sometimes the added jewels added to the durability and quality of the movement. Sometimes they served a marketing purpose only. This resulted in lots of 39 Jewel watches, some with 50 or more, and culminated with Waltham’s 100 jewel watch which featured 83 jewels set around the perimeter of the oscillating weight and the NIHS and ISO establishing standards for what could “count” as jewels in a watch. Today U.S. law requires “one or more of the bridges or top plates to show the name of the country of manufacture; the name of the manufacturer or purchaser; and in words, the number of jewels, if any, serving a mechanical purpose as frictional bearings.” So brands can’t advertise non-functional jewels in watches.
I recently worked on a Benrus watch with 39 Jewels. You will see in the photos that the movement is labeled 39 Jewels using a placard which was attached over top of the original label of 17 Jewels and you will find all 22 extra jewels installed in the reversers where they serve no functional purpose (11 in each reverser). At best, 3 jewels from each reverser could be considered “functional.”
So what makes a jewel functional? Let’s disregard the language of the NIHS and ISO standards and just look at where you find jewels in watches today and why.
The balance wheel of the watch is the most critical component of the watch for timekeeping. Balances are fit with a different style of a jewel than most of the other wheels (gears) in the watch. The balance rotates back and forth on an axle known as a balance staff. The pivots of the staff are supported by a system of capped jewels in a shock system. In a capped jewel system the pivot passes through a jewel with a hole and the tip contacts a flat jewel.
This system provides the same benefits as any other jewel, mainly reducing friction and wear, but it also provides an extra advantage of being able to equalize the effects of friction between horizontal and vertical positions. That is to say when the watch face is vertical the balance wheel is exposed to the same amount of friction as when the watch face is horizontal. This helps the watch keep better time. These are 4 of the jewels you would find in a 7 jewel pocket watch and in every modern watch. As an added bonus the cap jewel system can be fit into a shock protection system, but the cap jewel itself doesn’t provide any of that protection.
The escapement is the mechanism which delivers energy to the balance and keeps it oscillating so the watch will run. The Swiss lever escapement, used in most modern watches is a beautiful mechanism but it has some downsides, namely friction. This is why the co-axial escapement is considered to be a superior design because it eliminates the sliding friction of the escapement. There are 3 essential jewels in the escapement.
They are a roller jewel which is attached to the roller on the balance and two pallet stones that receive the impulse from the escape wheel. The roller jewel is the part that receives the impulse from the pallet fork. It is made from ruby to keep it from developing a flat spot due to the repeated impacts (at least 432,000 per day.) The pallet “stones” (that’s what watchmaker’s call the rectangular stones in the pallet fork) have a special geometry which uses sliding motion to convert the rotational energy of the escape wheel into a back and forth motion which is used to propel the balance wheel when the opposite end of the fork (the notch) strikes the roller jewel. These are the other 3 jewels in a 7 jewel pocket watch. In the photo of the escapement, you will notice that the pivot of the pallet fork arbor is also supported in jewels. These would be brass bushings in a 7 jewel watch but are usually jewels in all modern watches.
The gear train
The jewels in the gear train all share similar properties. The bottom of the jewel is flat. It has a hole drilled in it and the top has an oil sink (or little bowl) to hold the lubrication. Occasionally the train wheels will have capped jewels like the balance but usually they just have one jewel on each side, like the one pictured on the pallet fork. Two jewels for each of the wheels in the train (escape wheel, fourth wheel, third wheel, and center wheel) will bring the count to 17. A manual wind watch is considered “fully jeweled” if it has jewels all the way through to the center wheel.
A high-grade pocket watch with 23 jewels would have capped jewels on the escape wheel and jewels for the barrel arbor and barrel contributing 6 additional jewels.
The automatic winding mechanism often takes more abuse than the escapement so jewels are really important, however, some brands have released watches without any jeweled bearings in the automatic mechanism. This is far less common today than it was 25 or 30 years ago. The typical modern automatic watch has 17 jewels in the base movement and additional jewels in the automatic mechanism. The location and total count depends on the design. If the automatic mechanism has an oscillating weight with an axle, like many Rolex calibers, then the axle is usually supported by two jewels. If the mechanism uses ball bearings no jewels are necessary for the oscillating weight. The typical winding train in the automatic mechanism consists of 2 reversers and a driving wheel each of which will have 2 or more jewels. In the case of the Rolex automatic winding mechanism pictured (caliber 2235) the driving wheel actually utilizes 3 jewels bringing the total number of jewels in the automatic module to 9.
The base movement for the Rolex 2235 actually has 22 jewels and the total movement has 31. The base movement has capped escape wheel pivots, 2 jewels for the barrel, and a 3rd jewel to support the sweep seconds pinion. Add those to the 9 in the automatic device and you have 31 jewels. Interestingly enough there are also 4 more jewels in the date mechanism which don’t seem to be counted, probably because they don’t meet the strict rules of the NIHS for “functional jewels.”
In a chronograph mechanism, you might find jewels for some of the extra wheels needed to provide that complication. Occasionally you find a minute wheel post that is made from ruby if the manufacturer was afraid that a brass or steel post might not last. The more complications you add, the more jewels you will need. The Patek Philippe 6301P: Grande and Petite Sonnerie with minute repeater and dead seconds has 95 jewels! Every last one of them is there to help reduce friction (very important in a watch like that) and to make sure the components will last so you can hand the watch down to the next generation.
Today there are very few watches on the market that don’t have enough jewels. As a watchmaker, I rarely see a component in a modern watch that is unnecessarily worn, simply because the manufacturer chose not to use a jewel where they could have, however, I do see this in old pocket watches all the time. So, today, jewels aren’t so much a measure of quality as they were in days of old, but they are still really important. We do see some material innovation which is replacing jewels. The most notable being the use of ball bearings in automatic watches in place of an axle with jewels and silicon pallet forks which don’t need any jewels at all because the silicon has a “self-lubricating” characteristic which provides a very low coefficient of friction even without lubrication. So, with only a few exceptions: In order for your watch to keep running day after day without wearing out, it needs jeweled bearings. They reduce friction and prolong the life of your watch.