This page contains an overview of the major parts of a watch, as well as an explanation of how watches operate. Many complicated parts must all work in tandem in order to not only tell time, but perform a myriad of other functions. These could include a chronograph, altimeter, alarm, day/date calendar, moon phase, and slide rule bezel. Below are descriptions of the major internal and external parts and their functions.
The crystal is the cover over the watch face. Three types of crystals are commonly found in watches. Acrylic crystal is an inexpensive plastic that allows shallow scratches to be buffed out. Mineral crystal is composed of several elements that are heat-treated to create an unusual hardness that aids in resisting scratches. Sapphire crystal is the most expensive and durable, approximately three times harder than mineral crystals, and 20 times harder than acrylic crystals.
The bezel is the surface ring on a watch that surrounds and holds the crystal in place. A rotating ratchet bezel moves in some sport watches as part of the timing device. If rotating bezels are bi-directional (able to move clockwise or counter clockwise), they can assist in calculations for elapsed times.
The crown (often referred to as the winding crown or winder) is the nodule extending from the watch case that is used to set the time, date, etc. Most pull out to set the time. Many water-resistant watches have crowns that screw down for a better water-tight seal.
- Push/pull crown commonly usually found on most dress (non-water) watches.
- Screw-down crown commonly found on dive watches, a screw-down crown aids water-resistance by sealing the crown to the case of the watch. A seal is achieved when the case locks with the crown’s internal threads and gaskets fastening the crown into its place. In order to adjust the date and/or time on a watch with a screw-down crown, you must first unscrew the crown before you can gently pull it out to its first or second click stop position. To do this, simply rotate the crown counterclockwise until it springs open. When you have finished setting the watch, the crown must then be pushed in and screwed back in tightly. Not doing so will cancel the water-resistance of the watch. Overall, this process should not require a lot of effort or force.
The dial is the watch face that contains the numerals, indices, or surface design. While these parts are usually applied, some may be printed on. Sub-dials are smaller dials set into the main face of the watch. These can be used for added functions, such as elapsed times and dates.
The watch case is the metal housing that contains the internal parts of a watch. Stainless steel is the most typical metal used, but titanium, gold, silver and platinum are also used. Less expensive watches are usually made of brass that has been plated with gold or silver.
There are many methods for sealing down a case back. The primary methods for better water-resistance are screw-in and screw-down. Both serve the same general function, but there are subtle differences.
- Screw-in case back is recognizable by the notches along the outer edge. The entire case back is screw into place using a specialized tool that catches each of these notches. Despite its seemingly simple design, it is a very effective means of achieving up to 5ATM water resistance.
- Screw-down case back, like the name suggests, is fastened to the case using at least 4 separate screws. This method provides up to 10ATMs water resistance.
A bracelet is the flexible metal band consisting of assembled links, usually in the same style as the watch case. Detachable links are used to change the length of the bracelet. Bracelets can be made of stainless steel, sterling silver, gold, or a combination. A strap is simply a watchband made of leather, plastic, rubber or fabric.
The movement of a watch refers to the mechanics that power the ticking of the timepiece, and there are two main choices when it comes to analog watches (watches with hour hands and are not digital), quartz or automatic. What you choose really comes down to what you’re looking for in a watch. There are many ways to look at what’s attractive about both types of watches, but one way to look at it is the quartz watch as more practical and the automatic watch as more emotional.
- Quartz. The majority of watches made today utilize the vibrations of a tiny quartz crystal to maintain timing, with the power coming from a battery that needs to be replaced every 2 to 3 years. Watches with quartz movements are more accurate, losing about a minute of accuracy over a year, and they can have either analog or digital displays, or both.
Quartz watches work with a series of electronic components, all fitting together in a tiny space. Rather than a wound spring, a quartz watch relies on a battery for its energy. The battery sends electrical energy to a rotor to produce an electrical current. The current passes through a magnetic coil to a quartz crystal, which vibrates at a very high frequency (32,768 times a second), providing highly accurate timekeeping. These impulses are passed through a stepping motor that turns the electrical energy into the mechanical energy needed to turn the gear train. The gear train turns the motion work, which actually moves the hands on the watch dial.
- Automatic watches are made up of about 130 or more parts that work together to tell time. Automatic movements mark the passage of time by a series of gear mechanisms, and are wound by the movement of your wrist as you wear it. The gear train then transmits the power to the escapement, which distributes the impulses, turning the balance wheel. The balance wheel is the time regulating organ of a mechanical watch, which vibrates on a spiral hairspring. Lengthening or shortening the balance spring makes the balance wheel go faster or slower to advance or retard the watch. The travel of the balance wheel from one extreme to the other and back again is called oscillation.
Also referred to as self-winding, watches with automatic movements utilize kinetic energy, the swinging of your arm, to provide energy to an oscillating rotor to keep the watch ticking. They’re considered more satisfying to watch collectors (horologists) because of the engineering artistry that goes into the hundreds of parts that make up the movement. If you do not wear an automatic watch consistently (for about 8 to 12 hours a day), you can keep the watch powered with a watch winder (a great gift for collectors). You should refer to your owner’s manual for recommended service intervals.
- Chronograph enables you to use your watch as a stopwatch to time specific events as well as multiple laps. To start timing, you’ll press one of the pushers on the side of the watch case. Depending on the watch, you may press that pusher or a second one to stop the timing. Chronographs have two or three smaller subdials (also called totalizers or registers) placed on the dial face that display the seconds, minutes, and hours. Quartz chronographs can measure events down to 1/10 of a second, while their automatic counterparts can get as accurate as 1/5 of a second. In addition to timing your exercise, chronographs can be paired with a tachymeter scale (placed around the outside of the dial or on the rim of the bezel) to determine the average speed covered over a specified distance.
Note: Don’t confuse the term “chronometer” with a chronograph. Where a chronograph is part of a watch’s mechanics, a chronometer is a timepiece that’s been certified by the Controle Officiel Suisse des Chronometres (or COSC, the official Swiss chronometer inspection body) as being highly accurate. Only three percent of watches produced in Switzerland are chronometer-certified. To achieve this highly coveted certification, the movements are subjected to numerous tests over a period of 15 consecutive days and nights, in five positions and at three different temperatures. And a chronometer may or may not be a chronograph.
- Calendar. A small window showing the date, typically placed on the dial at 3 o’clock. You’ll also find some date watches that include the day of the week in a separate window. Most calendars count out to 31, requiring you to manually reset the date on those months that don’t have 31 days.
Some date watches have smarter calendar complications. An annual calendar can run for a full year without resetting until you get to March (as February’s 28 or 29 days throws it off). But you won’t have to worry about resetting the date for a long time with a perpetual calendar watch, programmed to automatically adjust for the varying lengths of months as well as leap years to the year 2100.
- Dual Time Zone and World Time If you do a lot of traveling, a dual time zone watch (also called a GMT watch) can be handy as it will show you the current time where you are as well as the time in a second time zone. This is done either via an extra hand, twin subdials, or a 24-hour scale placed on the dial. If you need to keep track of business time on several continents, a world time watch typically displays 24 city names placed on the dial or bezel to represent each individual time zone. You can read the hour in a particular time zone by looking at the scale set next to the city that the hour hand is pointing to.
Whether you’re a scuba diver or just a frequent dishwasher at home, you’ll want to pay attention to the water-resistance of your watch. Water-resistance ratings are listed in certain depths, typically in meters, but the numerical depth shouldn’t be taken literally. The depth rating actually represents the results of tests performed in a lab’s pressure chamber, and not real-world sea depths.
A watch marked as water-resistant without a depth indication is designed to withstand accidental splashes of water only. Do not submerge such a watch. Higher levels of water-resistance are indicated by increasingly higher acceptable depths, usually indicated in meters.
A watch with a back that screws onto the case provides a higher degree of water-resistance. Some crowns with a winding stem actually screw into the case to further increase water-resistance.
We do not recommend swimming or diving with your watch unless it has a screw-down crown (also known as ‘screw-lock’ or ‘screw-in’ crown) and is water-resistant to at least 100 meters.
Note: Water-resistance is sometimes listed using the abbreviation ATM, which stands for “atmosphere” and 1 ATM represents 10 meters. In Europe, “bar” is often used instead of ATM.
Below are typical water-resistance ratings and their corresponding parameters for real world usage.
- 30 meters (100 feet) / 3 ATM – Can withstand rain and splashes of water, such as car washing and showering, but it shouldn’t be worn swimming
- 50 meters (165 feet) / 5 ATM – Suitable for swimming, as well as higher altitude sports, such as skiing and parachuting
- 100 meters (330 feet) / 10 ATM – Suitable for snorkeling, as well as swimming
- 200 meters (660 feet) / 20 ATM – Suitable for recreational scuba diving
- 300 meters (990 feet) / 30 ATM – For use when scuba diving to a depth of 30 meters for up to 2 hours
- 500 meters (1650 feet) / 50 ATM – For use when scuba diving to a depth of 50 meters for up to 2 hours
Watches are typically measured in millimeters (mm), which might not be familiar to those of us without a lot of metric system experience. For a comparison, a United States quarter measures 24.26mm in diameter (0.96 inches), comparable to an average-sized woman’s watch. A larger-sized chronograph watch for men measuring 42mm in diameter is about the size of a regulation golf ball (1.68 inches).
Any given watch typically has three measurements:
- case diameter – an approximate watch measurement from one end of the watch to the other that does not include the crown
- case thickness – the thickness of the watch, measured from the highest point of the crystal to the base of the watch case
- band width – measures the distance between the case lugs. Therefore, band width may not necessarily be the exact width of the watch band, as a bracelet or strap can have tapering widths.
The latching mechanism that closes to secure the watch band to your wrist.