Introduction

In the world of watch repair, there are not a lot of points in history when new technology comes along that makes timekeeping more accurate and efficient. One important innovation involves the use of jewels, particularly rubies, in watch movements. Let’s explore the journey of jeweled bearings and how they contributed to reducing friction in watches and have made our work easier.

The Role of Ruby Jewels

For over 300 years, the finest watches have harnessed the power of ruby jewels to tackle a significant challenge: friction. These tiny rubies are used on the plates and bridges to reduce friction and ensure smoother movement. First let’s look briefly into their history and the pioneers who shaped this ingenious technique.

Pioneers of Jeweled Bearings

In 1690, Nicolas Fatio de Duillier-Figure 1, a Swiss mathematician, Astronomer and inventor discovered a groundbreaking method for drilling holes in jewels with a diamond drill.  Turned down by French watchmakers, Duillier would later partner with English watchmakers Peter and Jacob Debeaufre and obtained a 14-year patent on the drilling technique. These English watchmakers saw the potential and made a notable contribution by incorporating rubies into their watches, marking an important step forward.

Figure 1

Synthetic Corundum: A Game-Changing Discovery

Fast forward now to 1902, and another remarkable advancement comes into play. Auguste Victor Louis Verneuil, a French chemist discovered the “flame fusion” process, called the Verneuil process, which is an inexpensive method of making artificial corundum, or rubies and sapphires Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present. A rare type of sapphire, padparadscha sapphire, is pink orange. This innovation allowed for the production of high-quality synthetic rubies, further enhancing the use of jewels in watch mechanisms.

Challenges of Traditional Jewel Fitting

In the earlier days of jeweled watches, there were two primary methods for fitting jewels into watch mechanisms. The first involved bezel-setting the jewels in metal chatons-Figure 2, which were then screwed onto plates and bridges. Alternatively, jewels were burnished directly into specific holes on the plates or bridges and are known as Rubbed in Jewels-Figure 3. While effective, these methods presented challenges in adjusting end shake or the space between jewels to control the movement of wheels.

Figure 2
Figure 3

The Rise of Friction-Set Jewels

As watch production scaled up and manufacturing became more precise, new challenges arose. The need to account for tolerances in production and adjust the distance between opposing jewels became apparent. This led to the emergence of friction-set jewels in watches. These jewels were carefully placed to control the amount of end shake for the wheels, ensuring smoother and more accurate movement.

Evolution of Friction Jewels

In today’s world, the majority of watches utilize friction jewels to ensure smooth movement and accurate timekeeping. These friction jewels are secured in place primarily by the force of friction, making them easily adjustable. This innovation has evolved over time to address various challenges that watchmakers face.

Importance of Adjusting Jewels

While friction jewels offer improved performance, they aren’t invincible. Jewels can break due to various factors, and when they need replacement, they must be adjusted correctly to function effectively. Situations such as strong shocks, part replacements, or other actions can also necessitate the adjustment of these jewels to maintain optimal performance.

Precision in Friction Jewels

Achieving the right level of friction is crucial for proper jewel setting. To achieve this, the holes in bridges and plates that hold the friction jewels are meticulously machined to a diameter slightly smaller than that of the jewel itself. The difference in diameter is usually around 0.01 to 0.02 millimeters. This precise measurement ensures that the metal surrounding the jewel provides just the right amount of friction to keep it in place securely without unnecessary movement.

Balancing Friction

Finding the right balance in hole size is key. If the hole is too large, the jewel might move too easily, leading to instability in the power train and escapement. On the other hand, if the hole is too small, there’s a risk of the jewel cracking when it’s pressed into the hole. Achieving the correct diameter ensures that the friction jewel fits snugly and functions optimally within the watch mechanism.

Calibrated Reamers for Perfect Holes

Watch tooling manufacturers like the Seitz company produce sets of reamers-Figure 4, also known as broaches, which are carefully calibrated. These reamers create holes with exact diameters that are slightly undersized and perfectly match standard jewel sizes. This precision ensures a secure fit for the friction jewels within watch movements.

Figure 4

Tools for Adjusting Friction Jewels

Two primary types of tools play essential roles in the installation and adjustment of friction jewels. The first type is a micro metric adjustment tool (Horia)-Figure 5, featuring a threaded knob for fine-tuned positioning of the jewel. The second type is a lever-operated tool (Seitz)-Figure 6, requiring the watchmakers skill to delicately adjust the jewel’s position. Both tools contribute to precise adjustments in watch movements, and both have their advantages and disadvantages.

Figure 5
Figure 6

Variations in Horia Micrometric Jewelling Tool

The Horia Micrometric Jewelling Tool comes in two different versions. One version features pusher and stump sizes of 4mm. The other version has 4mm stumps and 3mm pushers. These tools are designed for specific purposes, and understanding the differences in their sizes will help us choose the right tool for the task.

Attachments: Vital Components

The attachments used with these tools are crucial for successful adjustments. The attachments include a pusher and anvil combination-Figure 7. Careful selection of attachments prevents damage to watch plates and jewels. The pusher design evenly distributes pressure across the jewel’s surface without touching the hole’s walls. Pushers are labeled with sizes in hundredths of a millimeter, slightly undersized to protect the plates.

Figure 7

Selecting the Right Pusher

For instance, a pusher labeled as number 70 suits a 0.70mm jewel diameter. In some cases, sets provide actual dimensions for more accurate choice. Ensuring the pusher is centered on the jewel enables precise adjustments without risking delicate components.

Spring-Loaded Precision

All jewelling sets should come with a special type of pusher known as a spring-loaded pusher-Figure 8. These pushers are designed with a clever feature – a spring-loaded center. This pointed center rod assists in positioning the jewel correctly below the pusher as you lower it into its designated spot. Now, picture this: the stump (the supporting structure under the jewel) should have a hole that’s just big enough for the jewel to fall through smoothly, without getting stuck.

Figure 8

Minding the Placement

When pressing jewels into place, keep in mind that the plate or bridge needs to sit flat. If you’re dealing with a watch plate that has multiple recesses at different levels, you might need to find a slightly smaller stump that fits into a recess. This way, the bridge or plate will sit flat without the stump causing any harm to the plate. Some plates and bridges might need a stump when removing the jewel but will be able to sit directly on the table when pressing in a new jewel.

Horia Tool: A Trusty Companion

In my workshop, I have 2 jewel press’s. The Horia tool is often cited as the preferred tool to use for adjusting end shake. This jewelling tool is the go-to choice for many watchmakers, and for good reason. If you need to make small adjustments to jewels, especially after replacing a worn wheel, the Horia tool can do it, but it has its limits. Its micro adjustment knob corresponds to moving the spindle by approximately 0.02 millimeters, allowing for fairly precise adjustments.  I have the Chinese clone version of the Horia tool and only use it to remove old jewels.

Lever Tool: Seitz Jeweling Press

For tasks involving very fine detail work the Seitz lever tool shines with its unique advantages. A built-in stop becomes a handy feature for measuring the depth of the old jewel.

In a repair shop scenario, this stop becomes quite useful, particularly when dealing with broken jewels. Let’s say you need to replace a damaged jewel. Here’s the method used: lower the pusher against the jewel’s acting surface (the opposite side of the oil sink). Set the stop to that point. Although the stop prevents the pusher from going further, it’s now primed for a smooth transition. To remove the old jewel, you’ll need a different tool. But when it comes to placing the new jewel, a simple push until the lever stops will align it perfectly.

You can’t do this with the Horia tool.

Other Advantages of the Seitz tool

One advantage of the Seitz tool is that the index is marked out in 100 indexes’ instead of 50 indexes’ like the Horia tool allowing for higher precision adjustments in the 1000’s of a millimeter.  

The Seitz press can also be used to remove damaged edges around jewel holes or even enlarge jewel holes to press in a wider jewel if you can’t find the correct center hole size.

Some other repairs that can be accomplished are closing plate holes when the jewel is slightly undersized or loose. You can ream out and burnish holes that have become oval in shape, tighten hour, minute, and seconds hand pipes, set watch hands, tighten cannon pinions and adjust the lever height on the pallet staff.

The Importance of Choosing the Right Tool

As we explore the world of jeweling tools, remember that selecting the right tool for the job is crucial. However, it’s not just about choosing the tool – it’s also about using it with care and precision. Remember: not all jewels are the same and you must use the right pusher for a specific type of jewel. Let’s delve into the various types of jewels available from the Seitz company and how they come into play.

Different Types of Jewels

Figure 9

The Seitz company offers five basic types of jewels, each with its unique characteristics-Figure 9. For instance, end stone or cap jewels are available in various diameters. However, experienced watchmakers know that these cap jewels might not always have the same thickness. While they can be a temporary solution, it’s advisable to use genuine jewels from the manufacturer whenever possible.

Balance Jewels

First, we have domed balance jewels with olive holes-Figure 9a. These jewels are specifically designed for watches without shock systems like Incabloc or Kif. They require a concave pusher to install these jewels because a flat pusher will break the jewel.  

  Now, when it comes to watches with shock systems like Incabloc or Kif, it’s best to opt for genuine components available from parts supply houses.

 Incabloc has developed a unique set of pushers and tailored for adjusting and replacing their shock jewel assemblies-Figure 10. Here’s a tip: when working with these components, make sure to apply pressure only on the outer part. Avoid pressing on the delicate inner parts to prevent any damage.

Figure 10

Oh, and one last thing to remember – traditional pushers might not be the best fit for Incabloc components. Their surface area is a tad too large and could potentially cause damage. It’s all about choosing the right tools for the task at hand.

Understanding Train Jewels

Now, let’s talk about train jewels. There are three types to choose from: flat jewels-Figure 9c with cylindrical holes, flat jewels with olive holes-figure 9b, and center wheel jewels-figure 9d. Center wheel jewels are specially designed to accommodate larger hole sizes and have unique oil sink shapes. Flat jewels with cylindrical holes are quite versatile and come in a wide range of sizes. On the other hand, for higher-end watches, flat jewels with olive holes might be more suitable due to their rounded shape, which affects the pivot’s contact with the jewel. These jewels all use flat pushers.

Replacement Considerations

When replacing cracked or broken jewels, it’s essential to stick with the same type. This consistency helps avoid issues with amplitude after completing the service. Remember, watchmaking is all about precision and understanding the nuances of different components.

Decoding the Jewel Hole Size

Once you’ve figured out the type of jewel you need and its outside diameter, the next puzzle piece is the size of the hole in the jewel. Now, here’s the smart approach: when replacing a cracked jewel, you’ll often want to work off the pivot. If the crack isn’t too severe and you have a pivot gauge handy, use it to measure the hole size before removing the damaged jewel.

Pivot Size: A Key Consideration

Now, imagine this scenario: the cracked jewel needs replacing, and you’re on the hunt for a new one. When ordering a replacement, it’s a wise move to match the hole size with the original. But wait, there’s more to it! Particularly in the case of older watches that have seen the hands of multiple watchmakers, or watches that have faced significant wear, it’s essential to check the pivot size too.

Measuring for Accuracy

If you’re replacing the component entirely, measure the new one before you proceed. On the other hand, if you’re planning to file and burnish (smooth out) the pivot to remove damage, make sure to complete that step before taking pivot measurements. Keep in mind that the size of the jewel hole should be slightly larger than the pivot itself.

The Art of Tilt: A General Rule

As you navigate this process, remember this rule of thumb: once placed in the jewel, the arbor (the part that rotates) should be able to tilt a bit, but not more than 5 degrees away from vertical. It’s all about achieving the right balance between movement and stability within the jewel.

Jewel hole sizes are given as actual dimensions, making things easier for watchmakers like you. Let’s say you have a pivot that measures 0.26mm in diameter. In that case, aiming for the next size up in jewel hole (0.28mm) is a sensible move. And if your pivot is slightly smaller than 0.26mm, you might find that a jewel with a 0.26mm hole is just the right fit. Here is a chart Showing the sizes available. Figure 11.

Figure 11

A Symphony of Science and Craftsmanship

As aspiring watchmakers, you’ve learned that every choice you make, from selecting the appropriate tool to measuring with precision, contributes to watch movements accuracy . Whether it’s the size of a jewel hole or the careful consideration of pivot dimensions, your dedication to detail ensures the accuracy and longevity of these mechanical marvels.

As you continue your horological journey, remember that watchmaking is a harmonious blend of science and craftsmanship. The world of tiny measurements and intricate components holds the key to timekeeping excellence. With every tick and tock, you’re participating in a timeless tradition that keeps the art of watchmaking alive and thriving.

Stay curious, keep learning, and let your passion for precision guide you as you embark on creating and maintaining timepieces that are not just instruments of time, but also testaments to your dedication and skill.

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