Hello, and welcome! I’m here to share with you some invaluable advice that could make all the difference in your watch repair journey. As a beginner, one of the biggest mistakes you can make is to rush into fixing a vintage watch movement without first understanding how things operate and look.

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Understanding Watch Tolerances

Hello, and welcome! I’m here to share with you some invaluable advice that could make all the difference in your watch repair journey. As a beginner, one of the biggest mistakes you can make is to rush into fixing a vintage watch movement without first understanding how things operate and look.

Let me explain, having a basic understanding of the workings of a watch is crucial to success. You simply cannot fix something if you don’t know what it’s supposed to look like. In other words, if you don’t know what the tolerances should look like, how will you know if they are not right or correct?

Watch parts are incredibly precise, and the tolerances between them are minuscule. Since it’s not possible to physically measure them, you need to learn how to look at the parts and develop a keen eye or develop muscle memory of what 2 hundredths of a millimeter looks like. For example, when looking at a wheel, you must be able to detect if there’s too much end shake or side shake in it. End shake is simply the amount the wheel moves up and down in its jewel hole and side shake is how much the pivots move side to side in the jewel hole.

Repairing vintage watches can be even more challenging. You never know if the parts inside the watch are correct for that particular movement, and you have no idea how many people have attempted to fix it before you and done something incorrectly but don’t worry, I’m here to help you develop the skills and knowledge necessary to tackle any watch repair project.

Inspecting a Watch Movement

Today, we’re going to start with our new St36 watch movement. We’ll learn about the tolerances that parts should have and develop a feel for them. This way, when you’re finally ready to repair a vintage watch, you’ll know what to look for and how to go about it. Remember, taking the time to learn the fundamentals is critical to success. So, are you ready to begin your watch repair journey? Let’s get started!

If you’re servicing a vintage watch, the inspection process is crucial, and it all begins with disassembling the movement. But before we dive into the nitty-gritty, we need to establish what’s right and what’s wrong. Unfortunately, tolerances between watch parts are so precise that they cannot be physically measured. Therefore, your point of reference will be visual, except for the dial side with the keyless works and motion works, where touch and feel come into play.

Checking Tolerances in the Keyless Works and Motion Works

To start, let’s get a feel for how much resistance there is between the stem and the mainspring as we wind the watch. When you pull the stem out to the second position, pay attention to how the yoke jumper and the setting lever interact with each other. These two pieces should interact seamlessly. Now pull the stem out to the hand winding position and feel for the friction between the cannon pinion and the extended arbor. You need to get a sense of how much resistance the cannon pinion requires to turn the hands.

The keyless works
The keyless works

Now, let’s move on to disassembling the movement. Begin by holding the click back and gently letting the crown slip through your fingers until all the power has been released from the mainspring. Then, we can remove the arrow wheel, the setting lever jumper, the yoke spring, and the yoke.

As we move on to the minute wheel, the most important thing to get used to seeing is the shape of the teeth. The more you study the shape of the teeth, the easier it will be to identify a tooth that’s gone bad or even a pinion leaf.

Studying the Teeth and Pinion of a Minute Wheel
Studying the Teeth and Pinion of a Minute Wheel

Moving on, we can remove the crown, the ratchet wheel, and the click spring and move on to the balance wheel.

Watch Inspection and Maintenance Tips

Checking Wheel End Shake, Impulse Jewel, and Pallet Fork

To check the end shake on wheels, an old oiler is the best tool to use. For the balance wheel, focus on the length of the pivot and how polished it should look. The bottom of the pivot should not be mushroomed out, but have a slightly rounded tip.

Balance Wheel Pivot and Impulse Jewel
Balance Wheel Pivot and Impulse Jewel

When looking at the impulse jewel, it should be straight up and down with clean, crisp edges and no chips. The hairspring’s coils should be evenly spaced, and the terminal curve going between the regulator pins should be nice and even.

Evenly Spaced Hairspring Coils
Evenly Spaced Hairspring Coils

Finally, when looking at the pallet fork, get a sense of what the end shake should look like by gently lifting the arm up and down with your tweezers. By developing a keen eye and feel for the tolerances, you’ll be on your way to becoming a watch repair pro.

Checking Pallet Fork End Shake
Checking Pallet Fork End Shake

 Mainspring Barrel and Train of Wheels

One of the most challenging areas of watch repair is the mainspring barrel. Mainspring barrels in vintage watches are notoriously over-lubricated, which attracts dirt and grime that gets in between the pivot and arbor holes in the bridge and plate. Over time, the pivot holes can become egg-shaped, causing the mainspring barrel to drag on either the main plate or the underside of the barrel bridge. Despite the lack of wear marks on the bridge or main plate, the mainspring barrel still needs to be running true in the arbor holes for maximum amplitude. So, having a visual reference on how much end shake a mainspring barrel needs is crucial.

Checking the End Shake on Mainspring Barrel
Checking the End Shake on Mainspring Barrel

As we delve deeper into the subject of amplitude, you’ll realize its importance to the timekeeping of the watch. The train of wheels is another area that requires precision, and looking at the end shake through a microscope requires consistent inspection methods. Your visual reference may be through a 10x or 15x  loop, so you must train your eye to differentiate between wheels that move more than others.

Checking the end shake of the third wheel pivot using an oiler or a probe can clearly show how much it’s moving up and down in the pivots.

Checking End Shake on Third Wheel
Checking End Shake on Third Wheel

But how do these jewels get out of place? Installing hands on a cannon pinion with too much pressure can move the jewels, or someone may have replaced the jewel without adjusting it properly. As a watchmaker, it’s your job to identify problems and fix them, but before you know what’s wrong, you need to know what’s right.

Bonus Tip for Determining Watch Jewel Condition

Determining the correct condition of a watch jewel is one of the easier things to do. It’s either broken or it’s not, and you need to be able to look at it clearly. The easiest way to do that is by laying the bridge on a couple of pieces of peg wood and shining a flashlight under it to illuminate the jewel from the underside. Any cracks or chips in the jewel will be visible right away.

Illuminated Jewel
Illuminated Jewel

In conclusion, by taking a careful and methodical approach to watch repair, you can become an expert in no time. Don’t be afraid to ask questions and seek guidance, and most importantly, practice, practice, practice.