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Watch diagrams

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Accuracy standards compared on a seconds per day scaleA number line from minus 30 to plus 40 seconds a day. METAS Master Chronometer spans 0 to plus 5. COSC chronometer spans minus 4 to plus 6. A good non-certified automatic spans minus 10 to plus 20. An entry level automatic spans minus 20 to plus 40. Quartz sits far off the chart at about half a second a day.How accurate is accurate?Seconds gained or lost per day, drawn to scale-30-20-100+10+20+30+40perfectMETAS Master Chronometer+0 to +5COSC chronometer-4 to +6Good non-certified automatic-10 to +20Entry level automatic, as sold-20 to +40A quartz watch sits far off this chart: roughly 15 seconds a month, about 0.5 seconds a day.
Accuracy bands. Certification buys a narrower window, not a different kind of timekeeping. Any mechanical watch is beaten by a $30 quartz.

Used in Do I need a chronometer?, How accurate is an automatic watch?, What does COSC certified mean?

Common watch beat rates comparedBars for four beat rates: 18,000 vibrations per hour equals 2.5 hertz, 21,600 equals 3 hertz, 28,800 equals 4 hertz and is the modern standard, and 36,000 equals 5 hertz. Hertz equals vibrations per hour divided by 7200.Beat rates, and what they cost youA faster balance resists disturbance better and wears out sooner18,000 vph2.5 HzVintage and slow beat. 5 steps a second.21,600 vph3 HzSeiko NH series and many workhorses. 6 steps a second.28,800 vph4 HzThe modern standard. 8 steps a second.36,000 vph5 HzHigh beat, more oil and wear. 10 steps a second.Hertz = vph รท 7200, because one full oscillation is two vibrations.
Beat rate. It sets how smooth the seconds hand looks, how well the watch shrugs off a knock, and how quickly the oil in the escapement is used up.

Used in Quartz versus mechanical: an honest comparison, Zenith, Miyota 8215

Cutaway of a watch case showing every gasketA side-on cutaway of a wristwatch case. The crystal sits on a gasket at the top, the caseback screws down onto a second gasket at the bottom, and the crown threads onto a tube sealed by a third gasket at the side. The movement sits in the middle, untouched by any of them.Where a watch case actually sealsCutaway through the case, with every gasket marked in brassMovementCrystal gasketCaseback gasketCrown tube sealthe one that fails firstCrystalCasebackThree seals in series. The rating is only as good as the weakest one.
Case seals. A water resistance rating describes the case as a system. One perished gasket, or one crown left unscrewed, and the number on the dial means nothing.

Used in Can I shower with my watch?, Why is there fog under my watch crystal?, Water resistance ratings, decoded

The energy chain inside a mechanical watch Energy flows left to right through five stages: the mainspring stores it, the gear train carries and divides it, the escapement releases it in equal packets, the balance wheel sets the size of each packet, and the motion works turns the result into hands. The keyless works sits below and connects to two of them, feeding the mainspring when you wind and the motion works when you set the hands. STORES CARRIES RELEASES REGULATES DISPLAYS Mainspring in the barrel Gear train four wheels, jeweled Escapement fork and escape wheel Balance wheel and hairspring Motion works the hands WINDS SETS Keyless works Crown pushed in: the crown winds the mainspring. Crown pulled out: the crown sets the hands.
The energy chain. Every part of a mechanical movement sits somewhere on this line, and every common fault can be located on it. Diagram: Timeless Ticks.

Used in How a mechanical watch works

The layout of a three register chronographA chronograph dial with a tachymeter scale on the bezel, subdials counting elapsed minutes and hours plus running seconds, a central brass chronograph seconds hand, and two pushers beside the crown: start and stop above, reset below.Reading a chronograph without the manualTwo pushers, three counters, one scale on the bezel6070809010012015020030040030minutes elapsed12hours elapsed60running secondsStart and stop pusherReset pusheronly when the chronograph is stoppedTachymeter bezelunits per hour from a timed lapBrass handthe chronograph seconds, still until you start itRunning secondsthe small counter that proves the watch is alive
Chronograph layout. The central sweep hand belongs to the stopwatch, not to the time. The small counter that never stops is the one telling you the watch is running.

Used in What is a chronograph actually for?, Chronographs: how they work and how to use one, Watch complications explained

The anatomy of a watch dialA watch dial with its parts named: the bezel around the outside, a chapter ring of minute marks, applied hour markers, a date window at three o'clock, a subdial at six o'clock, and hour, minute and seconds hands from the center.Every part of a dial has a nameReading a specification gets easier once the vocabulary is fixedsub31Bezelthe ring holding the crystalChapter ringthe minute track around the edgeApplied markersor printed, or lume filledDate windowquickset or not, that is the questionSubdialrunning seconds, or a chrono counterHandshour, minute, and a sweep seconds
Dial anatomy. Specification sheets assume you know these words. This is all of them on one dial.

Used in Dials, hands and legibility, Field watch vs pilot watch, The hands do not line up with the markers

The four case measurements that decide fitA top view of a watch case marking diameter across the case, lug to lug down the length including the lugs, and lug width across the gap where the strap fits. A side view marks case thickness including the crystal, above a curved line representing the wrist.The four numbers that decide whether a watch fitsDiameter is the one everybody quotes and the least useful of the fourDiameterLug to lugmust sit inside the flatof your wristLug widththe strap size to buySide viewThicknessincluding the crystalWristIf the lugs overhang the flat of your wrist, no diameter saves the fit.
Case dimensions. Lug to lug and thickness decide comfort. Diameter decides how the watch looks, which is why it is the number every brand prints and every buyer overreads.

Used in How do I measure my wrist for a watch?, Is a 40mm watch too small?, What is lug-to-lug distance and why does it matter?

How a Swiss lever escapement worksThree linked parts drawn side by side: a toothed escape wheel driven by the gear train, a pallet fork with two jeweled pallets that alternately lock and release the wheel, and a balance wheel with a spiral hairspring whose impulse pin nudges the fork at each swing.The Swiss lever escapementLock, release, impulse, repeat: eight times a second at 28,800 vphEscape wheelpushed by the gear trainPallet forkthe pallets lock and releaseBalancethe oscillator that sets the rateImpulse pin
The escapement. It has to do two contradictory jobs at once: hold the gear train still, and push the balance hard enough to keep it swinging.

Used in How long does a mechanical watch last?, Escapements: the hardest problem in watchmaking, How a mechanical watch works

How a GMT watch shows two time zones at onceA dial with a 24 hour scale around the outside and normal 12 hour markers inside. The ordinary hour and minute hands show local time. A brass 24 hour hand points at the outer scale to show a second time zone, turning once a day rather than twice.How a GMT hand reads a second time zoneOne extra hand, one turn a day024681012141618202224 hour scaleon the bezel or a printed ringBrass GMT handone turn a day, not twoHome timeread the GMT hand against the 24 hour scaleLocal timeread the ordinary hands as usualCaller vs travelerwhich hand jumps decides which you own
The 24 hour hand. Because it turns once a day, the outer scale can distinguish morning from evening, which a 12 hour dial cannot.

Used in How do I set a GMT watch?, What is a GMT watch for?, GMT and world time watches

Watch crystal materials compared on the Mohs hardness scaleHorizontal bars: acrylic at about Mohs 2.5, mineral glass at about 5.5, hardened mineral glass at about 7, sapphire at 9 and diamond at 10 for reference. Sapphire is highlighted.Crystal hardness on the Mohs scaleHardness resists scratches. It does not resist impact.AcrylicMohs 2.5Scratches from a fingernail's cousin. Polishes out with a cloth.Mineral glassMohs 5.5Shrugs off keys. Chips and shatters under a hard knock.Hardened mineralMohs 7Chemically strengthened glass, sold under brand names.SapphireMohs 9Only diamond and a few abrasives scratch it. Can crack.DiamondMohs 10Reference point only.
Hardness is not toughness. Sapphire resists scratching and acrylic resists shattering. Choosing between them is choosing which failure you would rather have.

Used in Is sapphire crystal worth it?, Sapphire, mineral and acrylic crystals, Sapphire vs mineral vs acrylic crystal

How power flows through a mechanical watchA left to right chain: crown or rotor, mainspring barrel, gear train, escapement, balance and hairspring, with a branch down to the motion works that drive the hands. A dashed line runs back from the balance to the gear train, showing that the balance controls the rate at which the train is allowed to turn.Crown or rotorenergy inMainspring barrelstores itGear trainsteps it downEscapementreleases itBalance wheeltimes itMotion workshands moveWhere the energy in a mechanical watch goesOne wound spring, five jobs, in this orderFeedback: the balance sets the pace of the train
Power flow. Everything a mechanical watch does is one spring unwinding, held back by an oscillator that only lets it go one beat at a time.

Used in What is an automatic watch?, How a mechanical watch works, Servicing and caring for a mechanical watch

Power reserve compared across common movementsBars showing hours of running from a full wind: about 38 hours for older ETA and Sellita movements, 41 for the Seiko NH35, 42 for the Miyota 9 series, 70 for modern long reserve calibers and 120 for multi barrel designs. A marker at 60 hours shows the threshold for a watch taken off Friday night and still running on Monday.Power reserve, and what it means on a Monday morningHours of running from a full wind, with the weekend test markedoff the wrist Friday night, still running Monday38 hoursOlder ETA and Sellita workhorses41 hoursSeiko NH35 and its relatives41 hoursMiyota 9 series70 hoursModern long reserve movements120 hoursMulti barrel and five day calibers
Power reserve. Anything under about 60 hours means a watch left off over a weekend will be stopped when you pick it up.

Used in How often should I wind my automatic watch?, Why does my automatic watch stop overnight?, Automatic versus manual winding

Water resistance ratings and what each one allowsFive stacked bars, growing left to right. 30 meters: rain and hand washing only. 50 meters: survives accidental immersion. 100 meters: swimming and snorkeling. 200 meters: repeated swimming and jumping in. 300 meters or a DIVER'S marking: scuba diving.What each water resistance rating really allowsThe marking is a static pressure test on a new watch, not a depth limit3 bar / 30 mRain, hand washing, a spilled drinkNo swimming5 bar / 50 mSurvives accidental immersionBrief, shallow swimming at most10 bar / 100 mSwimming and snorkelingThe first genuinely wet rating20 bar / 200 mRepeated swimming, jumping inUsually a screw-down crown30 bar+ or DIVER'SScuba, if it carries the ISO 6425 markEvery watch tested, not a sample
The ladder. Treat the printed figure as roughly three to four times the depth you should actually take the watch to, and treat anything under 10 bar as not for swimming.

Used in Can I swim with a 50m water resistant watch?, Can I wear a mechanical watch every day?, Is 100m water resistance enough for swimming?

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