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How a Watch Works
The fact you’re visiting our website, reading this article suggests you either know a little bit about watches already, or are at least aware that they are not powered by magic, and would like to find out exactly what makes them tick. There are plenty of informative articles all over the internet naming the basic components of a watch movement, but far fewer explaining what they actually do and how they impact a watch’s function overall. What we hope to do with this run-through is provide a starting point for those discovering to the finer details of horology for the first time, and to open a discussion with our readers so that everyone, old or new to the craft, can benefit from an open exchange of information.
To make things easier to visualize, we're going to walk through the major components of a watch movement in the order they are engaged, starting with your first interaction with the watch: Winding it!
While the crown is not (entirely) internal, it is one external component on every watch that directly engages with the inner workings. This is because it is attached to the winding stem. The stem is a long, multi-faceted stalk that plays an integral role in the function of the keyless work. Its threaded tip is screwed into the crown, while its main body engages with the winding and sliding pinions that are responsible for shifting between the winding position and the hand-setting positions.
The Keyless Work
The keyless work's name comes from the fact it replaces the need for a key to wind and set the watch. In the early days of watchmaking, all watches were wound with a key, and the hands were set with the same external tool. The invention of the keyless work is to thank for the ease of use we enjoy today. It has many components, some involved in winding the watch (which will we address here), and others that are responsible for setting the hands (which we will explore in a future article).
When in the winding position (the first crown position), the winding pinion engages vertically with the crown wheel, which sits flat against the barrel bridge. The crown wheel engages with the ratchet wheel and steps up the gearing from the rotations you make of the crown to deliver more efficient charging of the mainspring, which is what supplies the watch with power.
The ratchet wheel is large and often very visible when viewing a movement through a see-through caseback. It sits on top of the barrel, which contains the mainspring, and is screwed into the barrel arbor (a post running through the middle of the barrel). As the ratchet wheel turns, so too does the barrel arbor, which is hooked onto the end of the mainspring, resulting in the mainspring becoming tightly coiled around it.
The mainspring in its barrel effectively acts as a rechargeable mechanical battery. All of the power inside a mechanical watch originates in the mainspring. When the watch is “fully wound” the mainspring is coiled around the barrel arbor as tightly as it can be. The power is generated by the mainspring’s attempt to uncoil. Thanks to the escapement, which sits on the other side of the gear train, the mainspring is unable to unwind itself in one go (the escapement acts like a braking system, switching the power released from the mainspring on and off several times per second). The time it takes for a mainspring to fully unwind (or at least to the point at which it stops powering the watch due to a critical reduction in torque) is known as the power reserve. Traditionally, wristwatches did not have a hugely significant power reserve requiring them to be wound every day to continue functioning at an optimal level. Some modern watches have incredibly power reserves of several days, weeks, and in some very special cases, months.
The gear train is probably the first thing one thinks of when imagining the workings of a watch. It is the series of wheels that run through the center of the timepiece, converting the power from the mainspring (as regulated by the escapement) into increments of time. The gear train is commonly comprised of three or four brass wheels, which tend to stand out from the rest of the movement because of their golden color. In a watch with three, centrally-mounted hands, the wheel in the middle of the watch is attached to the seconds hand on the dial side and is thus geared to rotate once per minute. A different hand configuration would affect the way these wheels are geared, as does the operating frequency of the escapement.
The escapement is the regulating organ of a mechanical watch. These components, working in constant harmony, govern the watch’s heartbeat and ensure that the mainspring's power is correctly distributed to the gear train so the correct impulse is delivered to the hands so that they might tell the time.
The first component of the escapement is the escape wheel. It engages directly with the gear train. In fact, it very much looks like it is part of it, but it is distinguishable by its oddly shaped teeth (which looked like little riding boots). These “boots” kick into the Pallet Fork, which is a T-shaped component that sits between the escape wheel and the balance wheel. It is this component which effectively acts as a brake, jamming into the escape wheel teeth, preventing the gear train from advancing. The impact between the jeweled tips of the pallet fork and escape wheel teeth is what causes the famous ticking sound of a watch.
Were it not for the balance wheel and the hairspring, the pallet fork would jam into the teeth of the escape wheel and remain there, forever blocking the movement. However, the balance wheel vibrates back and forth at a set rate, moving the pallet fork in and out of engagement with the escape wheel as it passes by. The most common rates in the industry today are 28,800 vibrations per hour or 21,600vph. A faster operating frequency is more commonly found in automatic sports watches as it is more effective at surviving heavy shocks.
The pallet fork actually kicks the balance wheel on its way once it has, itself, been moved by the balance wheel so that the escape wheel may advance one tooth (or tick). This slight impulse helps keep the balance swinging at a healthy amplitude and aids in the overall function of the watch.
Please feel free to ask questions, or share your experiences of collecting and/or working on/with watches in the comments section below, and feel free to request technical topics you'd like to see covered or aspects of existing topics you’d like to see further explained.
This is going to be a whole lot easier if you’re wearing a watch…
Watch cases come in many shapes and sizes. They have many functions, too. Some are designed to withstand humungous pressures inflicted by the weight of oceans bearing down upon them, while others are built to hold up under the weight of judgemental dinner party stares. Whatever your watch’s case has been designed for, there are several things it will have in common with all others. Those components are what we’re going to explore here in this article. Please feel free to get in touch with us in the comments section below the article with any queries or additional information about your personal experience with less than normal watch case designs.
And while there will always be exceptions to every rule (that's pretty much the only constant in our industry) the following elements are likely to be sitting on your wrist right now, just waiting for their definition to pop up here.
Okay. Yes, this is basic, but the watch case is the thing that contains the movement/caliber, which is responsible for keeping the time. The case is essential for protecting your watch’s delicate internals from the world.
The case middle is the main body of the watch. Internally, the movement will likely be attached to this piece. The crown tube screws into the case middle, while the lugs emanate from it. The caseback is attached to its underside, while the bezel sits atop it. It is the foundation of everything and its silhouette can be the difference between becoming an icon and being forgotten.
The crystal or “glass” is the transparent bit of material through which the dial is viewed. Most luxury watches use sapphire crystal coated with an anti-reflective layer to reduce glare and improve legibility. Some brands use mineral crystal. This is quite often used for display case backs on lower-end brands, but it is never ideal. It can be chipped and cracked and is vastly inferior to sapphire.
Another alternative is perspex or hesalite crystals. These plastic options may sound flimsy, but they actually have some advantages. Aside from being much cheaper to produce, they bend light differently, giving a warmer view of the watch face. They can also be refinished by a trained hand, so even though they do pick up scuffs and scratches all hope is not lost when they do.
There are many different types of bezel. Some are completely static and simply frame the dial. Many, however, serve some function. They can be engraved with scales that can be used along with seconds hands or chronograph functions to perform several "useful" calculations on the fly.
The most common type of functional bezel, though, is the unidirectional rotating timing bezel used by divers to accurately track the length of their dive to ensure they do not stay submerged for too long and run out of oxygen. These bezels are often fully lumed so they can be read in low light conditions underwater, and when used in conjunction with a luminous minute hand can keep divers safe while they go about their business.
The crown is one of the most noticeable and well-known external features of a watch. Crowns are used to wind the watch and set the time, so they are the component with which most wearers will have the most to do. Crowns are also very important for the water-resistance of a watch and many feature single, double, or even triple gaskets as well as the ability to be screwed down to create a hermetic seal. Crowns are also ripe for branding, and many companies will "sign" the crown with their logo. This makes the preservation of crowns on vintage watches (which were often subjected to quite a battering) very important for value retention.
The caseback is the main access point to the movement for watchmakers. The vast majority of watches are "back-loading," with the movement and dial being inserted from the back. A few front-loading cases exist, but they are increasingly rare (which is a good thing, because many of them are a nightmare to service). Casebacks can be attached in several ways. The three most common types of caseback are snap-on backs, threaded casebacks, and screwed/screw-in casebacks. There can be a great deal of confusion between screwed/screw-in case backs and threaded casebacks as the former term could be said to accurately describe either a case attached with screws or one that is itself threaded and screwed into the case middle.
Generally, dive watches tend to have threaded casebacks as these are seen to be more water-resistant. There are, however, some dive watches that use a special type of case know as a "compressor." Compressor casebacks are spring-loaded snap-on backs that give a little under external pressure, compressing the components of the watch case and making it more water resistant the deeper it goes. These are often typified by two crowns (one at 2 o’clock and one at 4 o'clock), but dual crowns are not essential for the same technology to be implemented.
The lugs (or horns) are the protrusions from the main body of the watch that are used to attach the strap to the watch. In most watches, there are four visible lugs. Some unusually shaped cases do away with lugs entirely. In these cases, straps are sometimes attached to a notch in the side or underside of the case.
Some watches, like the Clerc Hydroscaph or IWC Da Vinci, have articulated lugs to enable to snugger fit to the wrist. Some brands, like Mortiz Grossmann in Germany or Tudor in Switzerland, have experimented in using their lugs for additional functions. The Moritz Grossmann Tefnut Twist watch features a winding system built into the 6 o’clock lug. Meanwhile, the recognizable Tudor Black Bay P01 uses hinged lugs to lock a rotating bezel in place.
Spring bars are not the only way of attaching a strap to a watch case, but they are by far the most common. They are simple tubes of metal with spring-loaded tips that can be compressed to about 4mm shorter than their fully-extended length. It is always best to get a professional to change a strap for you, but if you have the correct tools at home it is possible to perform the change a strap yourself with a little patience and practice.
Rather than spring bars, some watches use screw bars. These are much easier to fit and remove, but especial care must be taken to use the correct screwdriver head as using the wrong size or shape blade can burr the screw head, destroying its appearance (and, ultimately, use).