Overwinding of Mechanical Watches [With Facts]

There is a lot of debate about whether mechanical and automatic watches can be overwound or not. While there are some contradicting answers, there are several possibilities when winding watches. You and a lot of others are worried that the watch could break of overwinding (which is why you googled to find out). In general terms, there is some things to be mindful of, but breaking a watch with winding is quite difficult.

  • A mechanical watch can’t be overwound unless a lot of force is used. A mechanism will gradually build tension, hence indicating the watch is wound.
  • It is not possible to overwind an automatic watch. The slip-clutch will decouple the mainspring from the winding mechanism.

The winding of a movement is essential for the function of the watch. No winding = no timekeeping. In my best efforts, I will be trying to help you take care of your mechanical and automatic watch. Hopefully, you won’t break it the watch(es) you own by reading some of the helpful tips in this post.

Can Mechanical Watches be Overwound?

Whether a mechanical watch can be overwound or not is one of the most controversial topics in the watchmaking industry. Watchmakers say that it is impossible to overwind any modern watch because the watch is safeguarded against overwinding.

The typical watchmaker would instead say that the mainspring has snapped, which often has nothing to do with winding. A snapped mainspring could potentially bring along further damage, such as ripped teeth from the barrel or damage to the gears as all the store energy from the mainspring unloaded at once.

Overwinding a mechanical is possible, however highly unlikely. Modern watches builds tension as the mainsprings get wound, which indicates a fully wound watch. Overwinding the watch requires excessive force.

I will try to keep the explanation, however, it can get a little overwhelming to read and understand at first so be warned.

The power system itself consists of the barrel, cover, mainspring, arbor, ratchet wheel, and a click. the ratchet wheel is what is connected to the arbor and the gears that wind the watch. When you wind the watch, the racket wheel turns, which will turn the arbor, and therefore charge the mainspring.

The mainspring, which is attached to the center of the barrel, the arbor, starts to wind. A lot of people now assume the mainspring is unwound in the opposite direction. However, the click will engage at the ratchet wheel. Therefore the energy can be stored from winding but also make the barrel rotate through the mainspring.

The click ensures the ratchet wheel is locked in place and only allowing the ratchet wheel and arbor to rotate in one direction. This means the mainspring will unwind in the same direction.

As the mainspring unwinds friction from the inside wall of the barrel and the end of the mainspring drives the barrel forward. It is in this manner the barrel turns the same direction as the ratchet wheel is wound. The barrel when pushes the gear train, which starts the rest of the movement.

Now that we understand the way the mainspring works, we can also logically understand how it is possible to overwind the mainspring. Since the mainspring is attached to the arbor and is wound by the arbor, the mainspring will compress around the arbor when wound, and cram towards the barrel wall when unwound.

Logically we can overwind the mainspring by using excessive force as the mainspring would snap. The snap could be the mainspring itself. However, it could also be at the connection points.

Can Automatic Watches be Overwound?

Looking at how an automatic watch works, it could seem very likely that the watch would constantly overwind and snap the mainspring. Given the rotor will rotate all the time when the watch is worn, the mainspring is continuously charged, right? Actually no.

  • An automatic watch can’t be overwound due to the slip-clutch, which will engage and disengage as the mainspring becomes fully wound.
  • An automatic watch can’t be overwound from turning the crown nor from rotations of the rotor.

A power reserve on an automatic watch is typically more than 30 hours. Therefore if you wear the watch every day, you should have no reason to wind the watch manually, and the mechanism will protect itself against overwinding.

If the watch is serviced correctly, overwinding will never be a problem. However, to understand why you can’t overwind your automatic watch, I will go into detail to describe the mechanism which is actually quite simple but made from smart engineering.

In a typical mechanical watch, both ends of the mainspring is attached to something in the mainspring barrel. The inner part of the mainspring is connected to an axel (in watchmaking jargon called an arbor), whereas the outer end is connected to the wall or cover of the mainspring barrel.

Mainspring-of-a-watch (Credits: Hustvedt)

In an automatic watch, the inner end is attached to the arbor, while the outer end is able to spin or slip freely in the barrel. In the picture above, the right side is the inner end of the mainspring, which is attached to the arbor, whereas the y-shaped end is the outer end. The outer end forming the y-shape is called a bridle.

The mainspring is put into the movement to provide a force, or scientifically, torque. Therefore, a freely slipping end is not sufficient as the torque would deplete at the same rate it was wound. Having the bridle on the mainspring enables tension to be built before it starts slipping.

The bridle is not enough to build the tension required for the mainspring to function correctly. Therefore, watchmakers lubricate the wall of the barrel wall with grease that creates friction. While this sounds controversial as the rest of the watch is lubricated to reduce friction, it is true.

The grease will help to control the amount of slippage. Modern watches have small indentations to the barrel wall, where additional tension is put on the sides of the outer end of the mainspring.

The indentation helps the mainspring from slipping too far. If the maintenance of the watch is neglected, the wear on the wall can cause additional slippage of the mainspring. Further slippage means the watch will deplete faster, and the power reserve will be must shorter than expected.

The Difference Between Mechanical and Automatic Watches

Winding watches is essential for making it keep time. However, there are differences in when and how to wind, depending on the type of watch. Therefore, understanding the main difference between mechanical and automatic watches are essential to avoid damages.

Both mechanical and automatic watches are mechanical. The name automatic comes from the automatic winding when worn on the wrist. Both automatic and mechanical are made of metal components and is powered solely from the power stored on the mainspring. None of the watches are powered by a battery. They are driven only by their mechanical complications, known as movements.

The main difference between a mechanical and automatic watch is the rotor winding mechanism added to the automatic watch. The automatic watch has a rotor which charges the mainspring when worn on the wrist. It charges through the movement on the wrist, due to the weight balance from the rotor. The rotor is rotating when worn on the wrist due to gravity. The rotor complication is what should solely charge an automatic watch when worn daily.

Mechanical and automatic watches are both powered by a mainspring. Therefore, the mainspring needs power. To power the mainspring, the watch has to be wound:

  • A mechanical watch is wound by turning the crown in a forward direction. When a mechanical watch is fully wound, you will feel the tension beginning to build up. When you start to feel this tension, the watch is fully wound, and forcing it further can damage the watch.
  • An automatic watch is wound by wearing it on the wrist. A rotor is attached to a winding mechanism that charges the watch as the watch rotates. If an automatic watch has entirely stopped, it can be beneficial to turn the crown in a forward direction to get the watch started.

Watches powered by batteries are known as quartz watches and should not be wound. There are kinetic quartz watches that look like automatic watches because they feature a rotor as well. The rotor is what makes the kinetic energy and stores the power in a battery. These watches are not mechanical, they are mostly electronic and must not be wound. Quartz watches are easily identified by their one tick per second on the second hand. In contrast, mechanical and automatic watches have a sweeping hand, beating between 3 to 6 times per second, typically.

What is a Power Reserve?

The mainspring is what charges the movement (or watch) to actually function. Mechanical and automatic watches are build to deplete energy from the mainspring regardless of complications (chronograph, moon phase, GMT, etc.). The power reserve is what people refer to when talking about the duration of a fully wound watch. For example, if you see an ad for a watch with a power reserve of 30 hours, the mainspring can power the watch for 30 hours without winding.

The power reserve the period the watch can keep ticking without being wound. A power reserve of 30 hours, meaning the watch can run 30 consecutive hours before stopping. A power reserve is essentially the mainspring, which wound when turning the crown or rotating the rotor on an automatic watch.

The mainspring will deplete quickly when using complications such as chronograph, which will require frequent winding if used often. Moon phase, GMT, and alike complications is calculated into the power reserve. This is because the chronograph is not a constant ongoing function like the moon phase and the GMT functions.

The mainspring is coiled around an axle, which in watchmaking jargon is called an arbor. The cylinder which the mainspring is stored in looks like a part of the gears when you are looking at the movement of a watch. When looking through a transparent case back, the mainspring barrel will look like one of the biggest gears visible. Inside the mainspring barrel is the mainspring (obviously). However, there is a cover on top, which prevents the mainspring from being out of place. The cover is also why you can’t see the actual mainspring.

Mainspring barrel
Mainspring barrel

Some watches have power reserve indicators. A power reserve indicator is a method to display the remaining power. A power reserve indicator is very helpful to mechanical watches where the watch isn’t winding by itself. The power reserve indicator will display the remaining energy stored in the mainspring.

Generally, the power reserve indicators are reserved for luxury watches, whereas owners of “cheaper” models have to eyeball the remaining energy. Having an automatic watch removes this problem.

Automatic Watch Stops Overnight

There are cases where an automatic watch stops overnight. Needless to say, it is not a good sign if the watch stops overnight. It is not normal to have a fully wound automatic watch stop overnight. The watch might be damaged or not properly wound. Wind the watch 50-60 times to make sure it is fully wound, then see how long it runs before stopping. If it stops at the rated power reserve, the rotor might be broken.

Having an automatic watch stop overnight can happen for several reasons. However, it is generally not a good sign to see a watch that can last +30 hours to stop in less than 8 hours.

Reasons an automatic watch stops overnight:

  • The watch is not properly wound at bedtime.
  • Throughout the day, there is not enough wrist movement to charge the power reserve.
  • The rotor is damaged. It has decoupled from the gears that charge the power reserve. A shock has pushed it out of place and gotten it stuck against the case back or wall of the case.

Before running to the watchmaker to get a full stripdown of the watch you can be an investigation at home first. No matter what the power reserve says you need to wind the watch until you are certain it is fully wound.

A watch is usually wound after 30-40 turns of the crown. Therefore, turning the crown 50-60 times ensures the watch is wound to its full (if working correctly). Remember an automatic watch as a slip-clutch, which will make the mainspring slip. Therefore you won’t damage the watch.

If the power reserve is rated for 30 hours, and the watch stops after 30 hours, there is most likely something wrong with the rotor or mechanism connected to the rotor. On vintage watches, it is seen that a bulge on the case back has caused the rotor to get stuck on the bulge.

How to Wind a Mechanical Watch

Winding a watch is quite a simple task. Winding a mechanical watch can only be done in one way – turning the crown of the watch. It is just essential that force is not used to wind the watch. To make sure the watch has the torque needed to function properly you can make it a habit to wind the watch the same time every day.

Winding a mechanical watch:

  1. Remove the watch from your wrist. Attempting to wind the watch will put unnecessary stress on the internal components as your index finger will lift the watch by the crown – don’t do that!
  2. If the watch has a screw-down crown, unscrew the crown to its first position.
  3. Turn the crown clockwise, or forward, 20 to 40 times or until you feel resistance.

Winding the watch is necessary to make the clockwork go, and fortunately, it is easy also if you have never owned a mechanical watch before.

How Often Should You Wind a Mechanical Watch?

There is really no interval at which the watch should be wound. However, you obviously want to wind the watch before the power reserve is depleted. When a power reserve has 30 hours, the best thing to do is to wind the watch within the outer ends of the power reserve so the mainspring gets worn evenly so to speak.

A general rule of thumb is that a mechanical watch is most accurate when wound more than 30% of its total power reserve. Theoretically meaning you wound wind the watch every 21 hours with a 30-hour power reserve.

Another rule of thumb is to avoid winding the watch as much as possible. The force you contribute to the small gears and springs can be quite significant. While the watches are made to be wound, it is better to wind it smartly to avoid any unnecessary wear.

If you keep winding the watch every 5 minutes you expose the whole movement to a lot of unnecessary force. If the watch features a screw-down crown the threading can get worn, and all the gaskets in between will also get excessive wear.

Jonas Henriksen

AllInWatches is founded by Jonas, who has a great interest in mechanical watches. All aspects of manual and automatic (mechanical) watches is a big interest and have been a passion since 2015, where the first automatic watch was purchased. Seeing the transparent case back and discovering the heritage of watchmaking piqued an interest in horology.

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