How Mechanical watch movements work

Mechanical watches do not use batteries. They rely on physical components and stored energy: [1, 2]

The 4 main components which you will find in every mechanical watch are:

Mainspring: A coiled metal spring stores energy when wound. In hand-wound watches, you turn the crown. In automatic watches, a weighted metal rotor spins from the natural movement of your arm to wind the spring. [1, 2, 3, 4, 5]. This is the power source.        The mainspring will be found inside the barrel. The mainspring is wound up tightly inside the barrel of the watch. Sometimes you can have more than one barrel. They can be stacked. The barrel controls the release of energy from the main spring. It avoids fluctuations as the mainspring unwinds so it doesn't loose torque. This often why you will have more than two barrels sometimes stacked next to each other.
Gear Train: A series of small gears (wheels and pinions) takes the stored energy from the mainspring and passes it forward. [1, 2]. These interact with the watch's motion works (secondary wheels that control the various function of the watch such as the hour, minute, second hands, any complications such as the date, chronograph, etc). Often these gears ae hidden under the bridges.
Escapement: This mechanism acts like a gatekeeper. It releases the mainspring's energy in tiny, exact, and steady pulses rather than letting it spin out all at once. [1, 2, 3, 4]. There are different types of escapements. A traditional one is a Swiss Lever escapement. This is a wheel and a pallet fork.
Balance Wheel: This wheel spins back and forth (oscillates) at a fixed speed with the help of a tiny hairspring, controlling how fast the watch ticks. Sometimes called the oscillator. In the watch world people talk about Hz or vibrations/hr. What they are referring to is the speed at which the balance wheel oscillates. Lots of Swiss watches are 4Hz (28,800 vibrations/hr). This is what creates the tick sounds.

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Tying this all together

The balance wheel gets its energy from the mainspring, though indirectly. The mainspring acts as the primary power source for the entire mechanical watch, passing its stored energy through the gear train and the escapement before it reaches the balance wheel

The balance wheel acts as the timekeeping heart of a mechanical watch, regulating the raw power that flows from the mainspring through the gear train and into the escapement. It swings back and forth at a fixed frequency to meter out energy in tiny, exact intervals. [1, 2, 3, 4]

Mainspring & Gear Train

• Mainspring: Stored inside a barrel, the coiled mainspring holds the mechanical energy of the watch and tries to unwind all at once.
• Gear Train: A series of interlocking brass wheels (center, third, fourth, and escape wheels) acts as a transmission, speeding up and transferring the mainspring's raw torque toward the escapement. [1, 2, 3, 4]

The Escapement Bridge

• Escape Wheel: The final wheel of the gear train, which receives the unregulated force of the mainspring.
• Pallet Fork: A jewelled lever that catches and locks the teeth of the escape wheel, preventing the mainspring from spinning out of control. [1, 2, 3]

Interaction with the Balance Wheel

• Impulse Exchange: As the balance wheel oscillates, its tiny impulse pin strikes the pallet fork. [1, 2, 3]
• Lock and Unlock: This strike pivots the pallet fork, momentarily unlocking a tooth of the escape wheel. [1, 2]
• Power Return: The escape wheel gives a small push to the pallet fork, which in turn delivers a fresh pulse of energy back to the balance wheel via its hairspring, keeping it swinging. [1, 2, 3, 4, 5]
• Time Regulation: Each complete swing (beat) allows the gear train to advance by a fixed, uniform step, turning the watch hands at a steady, accurate speed

The Relationship Between Power and Regulation

• Power Source: The mainspring provides the actual physical energy that keeps the watch running.
• Regulating Organ: The balance wheel and its attached hairspring act as the heartbeat or metronome, controlling how fast that energy is released rather than generating it. [1, 2, 3, 4]

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Extras

Rotors 

These wind the watch mainspring automatically as you move.

Jewels

Usually red or pink.

They help reduce friction at key pivot points in the watch movement.

You will see them even on the pallet fork

Lubicants

These also reduce friction.

Some of these lubricants can break down over time.

Its the reason why servicing the watch is important

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Jewels in a watch are small, hard gemstones used as low-friction bearings inside a mechanical watch movement to support moving parts. [1, 2]

What They Are Made Of

Synthetic materials: Most modern watch jewels are made from lab-grown synthetic rubies or sapphires (crystalline aluminium oxide) rather than mined gemstones. [1, 2, 3]
History: Nicolas Fatio de Duillier and the Debaufres patented jewel bearings in 1704, originally using natural stones like diamonds, rubies, and sapphires before synthetic options became common in 1902. [1]

What They Do

Reduce friction: They sit between metal pivots, gear axles, and levers to keep metal-on-metal rubbing to a minimum.
Prevent wear and tear: Because synthetic ruby is extremely hard and smooth, it stops the metal pivots from wearing down quickly, which helps the watch keep accurate time and extends its lifespan.
Hold oil: Their smooth surface helps retain tiny drops of watchmaker's oil right where it is needed. [1, 2]

Common Types of Jewels

Hole jewels: Ring-shaped stones with a central hole that act as sleeves for rotating gear axles.
Cap jewels (Capstones): Flat, un-drilled stones placed on top of hole jewels to limit end-shake (vertical movement) on the balance staff and improve shock resistance.
Pallet jewels: Rectangular stones mounted on the ends of the pallet fork to lock and release the escape wheel.
Roller jewels (Impulse jewels): Small pins on a roller table that receive the impulse from the escape wheel. [1, 2]

What Jewel Counts Mean

17 jewels: The standard count for a basic, fully jeweled manual-wind mechanical watch (covering all critical friction points from the center wheel to the balance). [1, 2]
21+ jewels: Found in automatic (self-winding) watches or movements with extra functions like a date or calendar. [1, 2]
30+ to 200+ jewels: Used in complex movements like chronographs, perpetual calendars, or ultra-thin watches that require extra support components. [1, 2]
Marketing myth: More jewels do not automatically mean a better watch. Extra jewels beyond what the mechanics require are sometimes added purely for aesthetic or marketing reasons. Quartz watches generally do not use jewels because they lack the high-friction gear trains of mechanical watches

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