12 Hidden Watch Features Most Owners Never Use

Your Watch Can Do More Than Tell Time

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Pick up almost any watch with more than three hands and you will find features that most owners have never touched. A rotating bezel, a strange set of numbers around the dial, a tiny valve on the case side or a second hour hand may look like decoration, but each started as a tool. Many were designed for divers, pilots, racers and travelers, and they still work today. Learning what they do turns a watch from a status object into an instrument. It also helps you take care of it, since some features, like screw-down crowns, need to be used correctly to maintain water resistance. The twelve below come from watch glossaries, parts guides and explainers of complications. They are general descriptions, and details vary by brand, model and movement, so the manual for your own watch is the final word. Some functions require specific procedures, and using them the wrong way can damage the movement. A few apply only to mechanical watches, while others are found on quartz models as well. If your watch has an unfamiliar scale, hand or button, there is probably a purpose behind it, and discovering it can be one of the quiet pleasures of owning a good watch.

Crown Positions: Winding, Date and Time

The crown, the knob on the side of the case, is the control center of a mechanical watch, and pulling it out to different positions changes its function. On many automatic watches, the crown in position one, pushed in, is for winding the movement by hand, position two sets the date and position three sets the time, according to a parts guide. On a watch with a day-date complication, there can be extra steps. Some crowns have multiple positions and click gently at each stop. Turning the crown in position one winds the mainspring, which gives a watch with a stalled movement a quick start. When you set the time, avoid changing the date in the evening hours around midnight, typically between about nine at night and three in the morning, because the date mechanism is engaged and can be damaged. Always push the crown fully back in after setting. Layouts vary, and some brands use different arrangements, so check the manual. Learning the positions takes a minute and prevents the common mistake of forcing the crown the wrong way. It is the first hidden feature worth knowing.

The Screw-Down Crown

On dive watches and many sport models, the crown screws into the case like a tiny bottle cap. A screw-down crown seals the case against water, and it must be unscrewed before you use it and tightened again afterward to maintain water resistance, as watch guides explain. The mistake many owners make is forgetting to screw it back in, which leaves the watch vulnerable to water. Others try to pull it without unscrewing it, which can damage the stem. To use the crown, turn it counterclockwise until it pops free, then wind or set the watch as usual. When finished, press the crown against the case and turn it clockwise until it is snug, without overtightening. Never operate the crown underwater. The gasket inside the crown wears over time and should be checked during service. Water resistance ratings assume that all crowns and pushers are fully closed. If your watch has a crown that does not seem to do anything, check whether it is a screw-down type. A moment of attention is all it takes to keep the protection intact.

The Rotating Dive Bezel

The ring around the dial of a dive watch rotates for a reason. A diver uses the bezel to track elapsed time underwater by aligning the zero marker with the minute hand at the start of a dive. The elapsed time is then read from the bezel, in minutes, as the minute hand moves around. The bezel is made to turn only in one direction, counterclockwise, so that if it is knocked accidentally, it can only show a shorter elapsed time than the real one, which is safer for tracking air supply. On land, the same function works for timing anything, from cooking to parking meters to the time left in a meeting. Align the zero with the minute hand when you start, and you can read the time that has passed at a glance. Some bezels have a sixty-minute scale, while others have a 24-hour scale for a second time zone. The ratchet action should click firmly. It is one of the most useful features on a watch and the one most people use as decoration.

The Tachymeter Scale

Many chronographs have a scale of numbers printed around the edge of the dial or the bezel, and it is called a tachymeter. It lets you measure speed over a known distance. To use it, start the chronograph when you pass a mile marker, then stop it when you pass the next one. The number that the second hand points to on the tachymeter scale is your speed in miles per hour, or in kilometers per hour if you used kilometer markers. The scale works for any known distance, a sprint or a lap on a track. It is based on the calculation that sixty minutes divided by the time taken gives the speed. The scale only works for times shorter than a minute, so it cannot measure very slow speeds. It was made popular by racing watches, and today it is mostly a design element. Some owners believe it measures the distance based on speed, which reverses the real relationship. Try it on a long highway with mile markers, as a passenger, and see how accurately your watch matches the speedometer.

The GMT Hand and the Second Time Zone

A GMT watch has an extra hour hand that makes one full rotation in twenty-four hours, twice as slowly as the normal hour hand. Reading it against a 24-hour scale on the dial or the bezel, you can tell the time in a second time zone. Travelers use it to keep track of home time, and pilots and military personnel use it for Greenwich Mean Time or Coordinated Universal Time. A rotating 24-hour bezel allows a third zone to be tracked. Because the hand moves in a day cycle, it also helps you tell day from night in the other zone. Many modern GMT watches let you jump the local hour hand forward or back without stopping the watch, which makes adjusting to a new time zone quick. To set it, you pull the crown to the appropriate position and move the hands as the manual describes. The function came from the aviation industry in the 1950s, when long-distance air travel created a need for it. It remains one of the most practical complications for people who travel or work with people in other zones.

The Power Reserve Indicator

Mechanical watches store energy in a coiled mainspring, and a power reserve indicator shows how much remains. It usually appears as a small sub-dial or a window with a hand pointing from full to empty, sometimes marked in hours. A typical mechanical watch holds between roughly thirty-eight and eighty hours of power, depending on the movement, according to watch guides. The indicator tells you when the watch will need winding and prevents the surprise of finding it stopped. For an automatic watch, wearing it for a day or two usually keeps it wound, but if you rotate between several watches, the power reserve shows when it is time to give one some attention. Wind a stalled watch by turning the crown until the indicator shows a healthy reserve. Do not force the crown once the mainspring is full. Some indicators are on the back of the watch, visible through a display case. The feature is rare on simple watches and common on high-end models. For owners, it is a way to see the watch's energy at a glance, and a reminder that a mechanical watch is a small machine that runs on stored power.

The Helium Escape Valve

Some professional dive watches have a small button or valve on the side of the case, usually at the two or ten o'clock position. It is a helium escape valve, a one-way purge valve that opens when pressure becomes too great inside the case. The valve was designed for saturation divers, who live for days in pressurized chambers filled with a helium mixture. Helium atoms are small enough to seep into a watch case through the seals, and if the diver ascends quickly, the pressure inside the case can push the crystal off. The valve releases the helium safely. For the vast majority of owners, it has no practical use, since a recreational diver does not breathe helium mixes, and a valve may be a point of potential leakage. Some watches have an automatic valve that opens by itself, while others use a manual crown that you unscrew. Manufacturers include it as a mark of tool-watch heritage and capability. If you see one, you are looking at equipment for a very specialized job, and a reminder that dive watches were engineered for conditions most of us never meet.

Chronograph Sub-Dials

The small circles on a chronograph dial are sub-dials, and they do more than fill space. Depending on the model, one may show running seconds, another a thirty-minute counter and a third a twelve-hour totalizer for the chronograph. When you press the top pusher, the central seconds hand begins timing, and the sub-dials count minutes and hours. Pressing again stops the timing, and the bottom pusher resets it to zero. On some watches, a sub-dial shows the power reserve, the date or a second time zone instead. The layout is varied, and two-register and three-register designs are common. To use the chronograph, be sure the crown is pushed in, and note that timing for long stretches can drain a quartz battery or the mainspring faster. You can time anything: a cooking task, a lap or a phone call. A chronograph with a tachymeter lets you time and compute speed. The sub-dials are small, so legibility depends on the design. Experimenting with the pushers is a good way to learn how your watch works, and it is the feature that gives chronographs their appeal.

Super-LumiNova and How the Glow Works

The glowing hands and markers on many watches use Super-LumiNova, a photoluminescent material that charges from a light source and glows in the dark. A few minutes under a bright lamp or sunlight is enough to produce a glow that fades over several hours. The color of the glow ranges from blue to turquoise to green, depending on the formulation, and in daylight the paint appears cream or white. The material replaced radium, a dangerous radioactive substance used in early luminous dials, and it is safe and non-radioactive. The brightness depends on the thickness of the application and the type, with some brands using thick layers for longer-lasting glow. The glow does not last all night, so a watch worn in a dark room will gradually dim. To get the best effect, charge the watch before going to bed or before a dive. Some watches also have lume on the bezel pip, the small dot at the zero marker, which makes timing easier in the dark. It is one of the most visible pieces of watch technology, and one that you can recharge in seconds.

Tritium Gas Tubes

A few watches, including some from Ball and Luminox, use tritium gas tubes for lighting. Tiny glass tubes coated with a phosphor contain tritium, a radioactive isotope of hydrogen that emits low-energy particles. The particles excite the phosphor, which produces a continuous glow without needing to be charged by an external light. The tubes can glow for years, with brightness falling gradually as the tritium decays, which has a half-life of about twelve years. Tritium emits low-energy beta radiation that cannot pass through glass, and the amount in a watch is tiny, so it is considered safe to wear. Tubes are sealed and should not be broken. Some watches combine tritium with other lume. The advantage is reliable visibility in the dark, which is why military and expedition watches use the technology. The disadvantage is cost and the slow decline in brightness over a decade or more. If you see a watch with small tubes on the hands and hour markers that glow all night without a light source, you are looking at tritium. It is a rare example of everyday gear that quietly runs on atomic energy.

The Slide Rule Bezel

Some pilot watches carry a rotating bezel with a logarithmic scale that works as a circular slide rule. By lining up numbers on the bezel and the dial, the wearer can perform calculations: speed, distance, fuel consumption, unit conversions and time-and-distance problems. The Breitling Navitimer made the design famous, and it was used by pilots before electronic calculators and flight computers. The scale looks intimidating, but it follows a simple principle in which multiplication is done by adding lengths on a logarithmic scale. Instructions are provided by manufacturers, and learning to use it takes practice. A pilot might calculate how long a flight will take at a given speed or how much fuel is needed. Few people use it for real navigation today, as digital instruments are more accurate and easier. But some owners enjoy using it for everyday calculations, like converting miles to kilometers or tipping. Step-by-step instructions vary by model, so a dedicated guide or the brand's manual is the best place to learn. The slide rule bezel is a charming reminder that watches once served as analog computers.

Lugs, Spring Bars and Quick-Release Straps

The lugs are the horns that stick out from the case to hold the strap, and the distance between them sets the strap width you need. Straps are attached with spring bars, small spring-loaded rods that fit into holes in the lugs, or with screw pins on some watches. A quick-release spring bar has a tiny lever that lets you change straps in seconds without tools, and many modern watches and straps include them. Changing a strap is a simple way to change the character of a watch, from a leather band for dress to a rubber one for the beach or a nylon one for a trip. Measuring the lug width in millimeters before you buy is the key step. Be careful when removing spring bars, because they can fly off and scratch the case. Use the right tool and work over a soft surface. Check that the spring bars are secure after installing. A watch with drilled lugs, which have holes through them, is easier to work on. The feature is easy to overlook, but it is the one that lets you personalize a watch for any occasion.

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