Watch Movements: A Comprehensive Guide and FAQ

Watch movements, like the engines in cars, are the mechanisms that make the whole thing run, and if you're new to the world of avid watch enthusiasm, there's more to learn about them, and how they work, than you think. In this comprehensive guide to watch movements, we will attempt to answer every question that you might have about movements — their different types, their important parts, who makes them, and even a bit of history and trivia. 

What is a Mechanical Movement?

A mechanical movement, the oldest type of movement in horology, uses a coiled metal spring, called a mainspring, that releases energy as it uncoils through a series of gears to drive a weighted, oscillating wheel called a balance wheel. The balance wheel’s oscillations are linked to an escapement, which periodically releases the gear train to move the hands forward to record the passing of hours, minutes, and seconds. Originally, the mainspring needed to be wound periodically by hand, first by a key, then by a winding crown attached via a stem to the movement. Later, a type of movement was developed that could be wound “automatically,” through the motions of the wearer’s wrist.

What is the difference between a mechanical movement and an automatic movement?

It isn’t really a question of difference: the latter is simply a specific type of the former, à la a Cognac and a brandy. The two main types of mechanical movements are manually wound (or “hand-winding”), in which the user needs to periodically wind the watch via the crown to keep it working; and automatic (or “self-winding”), in which the mainspring is wound by a rotor (or “oscillating weight”), usually a rounded semicircular mass that swings with the natural motions of the wearer’s wrist. Continually wearing this type of watch will “automatically” wind it. Conversely, if the watch remains motionless for too long — say, in a safe or on a nightstand — its mainspring will run down and the watch will need to be wound and set again to start timekeeping anew.

Are there different types of automatic movements?

By definition, all automatic movements use a moving weight connected to a gear train to wind the mainspring via the motions of the wearer’s wrist, so — aside from any additional complications incorporated into a given movement — there is very little difference mechanically in how they function. There are, however, different types of rotors. The most popular is a center-mounted, semicircular mass that somewhat resembles a hatchet blade, can swing in either one direction or both, and covers about half of the back side of the movement when it’s at rest.

Some watches opt for a micro-rotor (above), a smaller version of the traditional semicircular rotor that does the same job but is recessed into the movement rather than mounted above it, allowing for the overall mechanism to be thinner. Piaget, which is known for ultra-thin watches, was one of the pioneers of this type of rotor, which is also used by brands such as Patek Philippe and Parmigiani Fleurier.

Another, rarer type of rotor is a peripheral rotor (above), which is designed to swing around the edges, or periphery, of the movement, the advantage being that the rotor doesn’t obscure the mechanical beauty of the components behind it as a traditional rotor does. Carl F. Bucherer was the first watchmaker to make a peripherally wound automatic caliber part of its regular lineup, and some other companies such as Cartier, Breguet, and Vacheron Constantin have also adopted it in some movements.

What was the first automatic movement?

The first successful example of an automatic winding system is attributed to Abraham-Louis Perrelet (above), the founder of the modern Perrelet watch brand, in 1777.  Shortly thereafter, a French inventor named Hubert Harton improved upon Perrelet’s design, and his version was subsequently refined by Abraham-Louis Breguet, who made the first self-winding watches that were sold to the public around 1780. These Breguet “Perpetuelle” pocket watches (below) fell out of favor around 1800, however, due to their inconsistent reliability (remember, pocket watches weren’t worn on the wrist and couldn’t benefit from a constant flow of dynamic wrist motions to wind the rotor). When wristwatches began supplanting pocket watches during World War I, automatic movements made a comeback: British watchmaker John Harwood filed the first patent for a self-winding wristwatch in 1923 and the style has been around ever since.

What is a power reserve?

A watch’s power reserve (sometimes more formally called its running autonomy) is the amount of time its fully wound watch movement will continue to run, and tell time accurately, before it stops. Here again, an automotive analogy is apt: think of the mainspring barrel as a fuel tank. When it runs out of fuel — i.e., when the torsioned mainspring has fully stopped uncoiling, depriving energy from the gear train that drives the hands — the watch stops. The longer the power reserve, essentially, the longer you don’t have to worry about winding the watch. Some watches incorporate a visual indicator for the power reserve on their dials, as demonstrated on the Grand Seiko dial pictured below (or even on the backside of the movement if it’s visible behind an exhibition caseback). In reality, such a power reserve display is much more useful on a manually wound watch, as its power will run down regardless of how long and how often you wear it; as stated above, an automatic watch will stay perpetually wound unless it goes unworn for a period of time that exceeds the power reserve. (This, incidentally, is why Rolex uses the term “Perpetual” in the name of all of its watches with automatic movements.) Quartz movements and other types of electronic mechanisms, incidentally, don’t measure their reliability in power reserves but in battery life.

How long is a watch’s power reserve? What is the longest? 

Generally, most mechanical watch movements these days offer power reserves between 40-50 hours, though of course many watchmakers take pride in developing movements that store power far longer than the industry average. All of Panerai’s in-house movements, for example, have a power reserve of at least three days, or 72 hours, with some of them even storing 10 days’ worth of reserve. For its first in-house movement, Oris shot for the stars, power-reserve-wise, with its Caliber 110 and its offshoots amassing 10 days’ worth of power when fully wound. IWC makes the automatic Caliber 52010, which packs 192 hours, or eight days, of power reserve. Parmigiani Fleurier makes an eight-day manually winding movement for its Kalpa Hebdomadaire watch, whose name (French for “weekly”) indicates that it only needs winding once per week. At the highest level in this category are A. Lange & Söhne’s Lange 31, which holds, as it name implies, a full 31 days of power reserve, and the current record holder, Hublot’s MP05 La Ferrari, whose supercar-engine-inspired movement can run for an astonishing 50 days without a rewind.

What is a quartz movement?

As I explain much more thoroughly in this article, a quartz movement is one that eschews a mainspring barrel in favor of a small battery whose electrical charge passes via an integrated circuit into an oscillating crystal made of quartz, cut into the shape of a tuning fork. The crystal vibrates at a head-spinning rate of 32,768 times per second — much faster than the 3 or 4 times per second offered by most mechanical oscillators — to drive the hands at an incredibly precise rate, making for a watch that is accurate to -/+ 5 seconds per month; mechanical movements, in comparison, are considered accurate if they can achieve a few seconds of deviation per day. The Japanese are credited with being the pioneers of quartz technology in watchmaking, and the first watch with a quartz movement was the Seiko Astron, equipped with the groundbreaking Caliber 35A, launched in 1969. The benefits of quartz to the watch industry were several: quartz watches could be mass-manufactured easily and inexpensively and they were much more accurate than mechanically driven watches. 

If you’re approaching this from a very basic level, think of it this way: If your watch occasionally needs a battery change, it has a quartz movement. If it hasn’t needed one yet but you paid $200 or less for it, it probably has a quartz movement (though there are a few notable exceptions to this rule, as you’ll find here. 

Is Seiko’s Spring Drive movement a quartz or a mechanical movement?

The Seiko Spring Drive, first rolled out in 1999, is sort of a hybrid, essentially combining the high torque of a traditional mechanical watch with the high precision of a quartz one. In a Spring Drive caliber, energy is generated by a mainspring that is wound manually via the crown or automatically via the motions of the wrist. The rotor or “glide wheel” in a Spring Drive movement rotates very fast, generating a slight electrical current that is transferred to a quartz oscillator vibrating at 32,768 Hz, which is then transmitted to an integrated circuit (IC) that compares the reference signal from the oscillator with the speed of the glide wheel and regulates the latter with a magnetic brake. This electromagnetically regulated rate is transferred to the gear train to move the watch’s hands with utmost precision. Spring Drive movements are exclusive to Seiko, and are found in both Seiko and Grand Seiko watches. 

Don't some movements get their energy from sunlight?

Some watch brands use quartz movements whose rechargeable batteries draw power from solar cells activated by external light sources — not only from the sun’s rays, despite the catch-all term "solar powered" that is usually attached to them. The most famous and successful of these types is the Eco-Drive technology developed by Japanese watchmaker Citizen in 1976. That year saw the release of the first commercially available, light-powered analog watch, the Citizen Crystron Solar Cell. The technology was new and the battery life for those early models was low, so Citizen continued upgrading, releasing a watch in 1986 that could run on a single charge of light for eight days and another in 1995 that ran for six months on a single charge. The first Citizen Eco-Drive watches, powered by the Caliber 7878, were launched in 1996, equipped with the groundbreaking technology that is still at the heart of the Eco-Drive movements today: light passes through a translucent dial with a solar cell mounted directly underneath it, which supplies power to the lithium ion battery of the movement below. If being environmentally conscious is important to your watch purchasing decisions, it’s worth pointing out that solar-powered movements like Eco-Drive are “greener” than traditional quartz because they drastically reduce the number of dead batteries in landfills. (You can learn more about solar timekeeping technology here.)

What are the most important parts of a watch movement and how do they work?

The mainplate is the flat, usually disk-shaped, metal plate on which the rest of the movement parts are built. Traditionally made of brass, but occasionally of other materials like German silver or even gold, the mainplate is the foundation on which the movement is built, attached via screws to the bridges that hold the wheels, gears, and other components.

The mainspring is the spiral, torsioned spring made of metal ribbon that serves as the main power source of a clock or watch. Winding the mainspring builds up energy by tightening its coils around its arbor; as the spring untightens, it drives the movement’s wheels via the gear train. Usually 20-30cm in length, the mainspring is contained within a toothed mainspring barrel to prevent it from unwinding. (An additional mainspring barrel can be added to increase the movement’s power reserve). The barrel bridge that hosts this assembly is the second largest part of the movement.

The crown is the wheel on the outside of the watch, connected to a stem, that winds the movement in a manually winding watch and also sets the time.

The gear train or wheel train is the interconnected system of gears that transmits the energy from the mainspring to the escapement. 

The escapement is the brakelike device that regulates the energy transmitted by the gear train, releasing it in controlled impulses to the balance wheel.

The balance wheel is the weighted wheel that rotates back and forth, regulated by the escapement, whose oscillations, or beats, drive the hands forward. It is mounted on a balance spring, or hairspring, the spiral spring that controls its frequency and thus the rate of the watch. This assembly is mounted on a balance bridge.

Jewels, or jewel bearings, are tiny, durable pieces of synthetic ruby or sapphire that are set into drilled holes at specific areas of the movement that are particularly susceptible to stress — like the escapement, the balance, and the gear train — in order to reduce friction. A high jewel count doesn’t necessarily mean the watch is more valuable, but it does speak to the movement’s reliability.

The rotor, found only in an automatic movement, is the weighted semicircular mass that winds the mainspring, whose 360º rotations are activated by the motions of a watch wearer’s wrist. Rotors (or “oscillating weights”) are traditionally made of heavy metals like gold, tungsten, or platinum.

An ébauche is an incomplete “movement kit,” composed of  plates, bridges, wheels and barrels but minus essential elements like the escapement, hands, and mainspring that are supplied separately. Watchmakers that do not build the entirety of their movements in-house order ébauches from outside suppliers and use them as "base movements."

What does “manufacture” mean when applied to a watch movement?

In the strictest definition of the term, a manufacture movement is one that has been designed and produced entirely in-house by the company that makes the watch; this would include the design and production of all of the movement parts, from the mainplate and rotor down to the hairspring and screws. The term has become rather murky, and very much marketing driven, in this age of competitive luxury-watch prestige. Very few watchmakers would qualify as a true manufacture under these criteria mostly because very few of them have the capacity to produce their own hairsprings; among these few are Rolex, Patek Philippe, and A. Lange & Söhne. Even Berner’s Dictionnaire Professionale Illustrée d’Horlogerie, regarded as the watch industry’s Bible, defines manufacture as “a factory in which watches are manufactured almost completely [emphasis mine], as distinct from an atelier de terminage, which is concerned only with assembling, timing, fitting the hands and casing.”

Under this slightly broader definition, many more watch brands can qualify as manufactures, whether they make all or most of their movements in-house, like Jaeger-LeCoultre (above), Vacheron Constantin, and Zenith; or use both in-house movements as well as outsourced movements (often with in-house-made modules to add complications) in their watches; watchmakers like Breitling, TAG Heuer, and Oris are among the examples. The loosest definition of the term “manufacture” involves a movement that is designed in-house and contracted out to an outside supplier which then builds it exclusively for the contracting company, to that firm’s specifications. The more proper term for this type of movement is “proprietary,” a term that can be fairly applied to movements like Longines’ Caliber L888.4, made for the brand by ETA; Tudor’s Caliber MT5813, developed in a collaboration with Breitling; and Raymond Weil’s Caliber RW 1212, made in partnership with Sellita. 

If a watch company doesn’t make its own movements, where does it get them?

There are several firms that specialize in making watch movements and that supply them to a large number of client firms within the watch industry. Probably the most well known and prolific of them is ETA, which is owned by the Swatch Group, the Swiss conglomerate that also owns a number of watch brands, including Omega, Breguet, and Longines, as well as Swatch itself. Watchmakers inside and outside the Swatch Group use ETA movements (mechanical and quartz); many also refine, customize, and rename them for branding purposes: Breitling’s Caliber 13 and IWC’s Caliber 79350 are among many chronograph calibers based on the popular ETA 7750. Another Swiss supplier of movements is Sellita, which in recent times has broadened its customer base while ETA has reduced its sales to companies outside its parent group. Oris, Bell & Ross, and Frederique Constant are on the roster of brands that regularly use Sellita calibers. La Joux-Perret is a Swiss company, now owned by Japan’s Citizen Group, that specializes in complicated movements and modules, supplying them to brands including Carl F. Bucherer, Baume & Mercier, and two that the firm owns, Arnold & Son and Angelus. Vaucher, which is technically under the corporate umbrella of Parmigiani Fleurier, is another high-end movement purveyor (pictured above) whose other customers include Hermès and Richard Mille. Japan’s Miyota, another Citizen-owned company, provides mechanical and quartz movement for Swiss as well as Japanese watch brands, generally on the more affordable end of the spectrum such as Bulova and Timex.

What is a skeleton movement?

A skeletonized (or “openworked”) movement is a mechanical movement in which many of the components’ non-essential areas have been stripped away, leaving only the “bare bones” of the original mechanism and thus allowing for a deep view into the inner workings when the movement is mounted behind a clear dial. Most skeletonized movements start out as standard ones but some are built from the ground up to be skeletonized, as in Roger Dubuis’ Excalibur Spider Skeleton models. 

What types of decorations are found on movements?

A portion of every watch’s price comes from its movement, and the level of decoration on the movement determines how expensive that movement is to make. As with many aspects of high watchmaking, even many of the decorative techniques have practical origins: historically, textured surfaces applied to movement parts like the bridges and plates prevented dust inside the case from clogging up the works and slowing down the watch. In these modern days, when cases are much more dust-proof as well as waterproof, and with many cases now using clear sapphire panes in their backs to showcase the movement, these traditional techniques, some of them still largely hand-applied, are now mostly ornamental, adding value to the overall timepiece and spotlighting the artisanal skills of its maker.

The most commonly seen decoration is côtes de Genève, (Geneva waves, also known as Geneva stripes, above), a series of parallel or semicircular lines abraded into the surfaces of large movement parts (bridges, plates, etc.); as the name would imply, Swiss watchmakers in Geneva were the first to use the technique, which would also be adopted by German watchmakers and named Glashütte waves, or Glashütte stripes, in honor of that country’s main watchmaking town. 

Perlage (“pearling,” also called circular graining, above) is another common embellishment found on movement parts; it’s basically a textured pattern of overlapping small circles produced with a rotating abrasive  tool. “Anglage” (below), or chamfering, involves filing the edges of parts to sharp, clean right angles and then polishing these symmetrical, sloping edges to a high shine.

Another once-utilitarian element that adds aesthetic appeal are blued screws (below). Because screws needed to be hardened more than the movement parts they hold together, they were heated at higher temperatures in the tempering process, rendering them a bright shade of blue. Most high-end watchmakers still use this traditional “thermal” technique rather than achieving the bluing through a chemical process. 

The rotors of automatic movements are often a canvas for various types of decoration, including engraving of brand names (as below) or other motifs, or even intricate guilloché patterns like the ones used on dials.

What is a chronometer movement, and is it more accurate?

Originally, the term “chronometer” (not to be confused with a chronograph, which is a timekeeper with a stopwatch mechanism) was simply used to describe any instrument designed to measure time with exceptional accuracy. Today, within the watch world, a watch that purports to be a chronometer is generally one that meets strict criteria for accuracy as determined by a testing agency. Foremost among these agencies is Switzerland’s COSC (Contrôle Officiel Suisse des Chronomètres), a non-profit testing institute to which many luxury watch manufacturers submit their timepieces for certification as a chronometer. To receive the badge of honor that is a COSC chronometer certification, a mechanical movement must undergo a 15-day regimen of tests in several different positions and achieve, among other criteria, a daily average precision of -4/+6 seconds. (COSC also tests quartz movements using different criteria.) Only about 3% of Swiss watch production carries a COSC chronometer certificate.

Some watch companies have established other criteria for chronometric excellence that are even stricter than COSC’s. Omega’s “Master Chronometer” certification (seen below), for example, combines a COSC certification for the movement with an additional series of tests for the final watch conducted by the Swiss Institute of Metrology (METAS). The daily rate variation for Master Chronometer certification is 0/+5 seconds (a range of five seconds’ deviation compared to COSC’s 10 seconds). Most notable among the eight criteria of the METAS tests are a magnetic resistance to 15,000 gauss, a standard that very few watches can meet. Some brands have even developed their own in-house certification and testing regimens with higher chronometric accuracy standards than COSC’s: Patek Philippe applies its own Patek Philippe Seal to watches whose calibers achieve a daily rate of -3/+2 seconds, for example, and Grand Seiko awards its “Special Standard” label to mechanical movements that achieve a variation of +2/-4 seconds per day. Rolex, and only Rolex, uses a designation called “Superlative Chronometer,” which applies to watches tested by both COSC and Rolex’s own in-house team to achieve a +/-2 seconds daily rate. 

Are there other questions you have about watch movements that you'd like us to address in subsequent updates to this article? Let us know in the comments section.