Watch parts glossary
What the case, crown, lugs, spring bars, bracelet, clasp and movement are, plus quartz, mechanical and automatic movements explained in plain British English. To see each part on a real watch you can turn in 3D, play Lesson 1.
Outside
- Case
- The metal body that holds the movement, dial and crystal and protects them. Look for dents, deep scratches and edges rounded by polishing.
- Case back
- The cover underneath the case. It may screw down, snap on or be held by screws, and often carries the reference, calibre and case number. Opening it lets dust in, so in the school it stays closed.
- Bezel
- The ring round the crystal. On a dress watch it is usually fixed; on many divers' watches it turns, so it can time something. Older books use 'bezel' for the ring that holds the crystal.
- Crystal
- The clear cover over the dial. Acrylic is common on vintage watches and can be polished; mineral glass and sapphire are harder. Fog under the crystal means moisture got in: stop wearing the watch and have it looked at.
- Dial
- The face you read the time from, with its markers (indices or numerals) and any windows. Never scrape old luminous paint: some vintage luminous dials can be hazardous.
- Hands
- The hour, minute and seconds hands. They should be straight and clear of each other, of the dial and of the crystal.
- Day and date window
- An opening in the dial showing the day and date discs. A date that sits off centre in its window is worth noting.
- Crown
- The knurled button at the side, usually at 3 o'clock, that winds a mechanical watch and sets the time and date. Check its type before you operate it.
- Screw-down crown
- A crown that screws onto a threaded tube to seal the opening against dust and water. It must be unscrewed before winding or setting, and never forced.
- Lugs
- The horns on the case that hold the strap or bracelet, joined by spring bars. Look for wear, cracks or bending.
Bracelet and strap
- Spring bar
- A small sprung pin between the lugs that holds the strap or bracelet. Both ends must sit in their holes; a pin that sticks out means the strap could come loose.
- Bracelet
- A metal band made of links joined by pins or screws. Links can be added or removed to fit a wrist.
- Strap
- A band of leather, fabric or rubber, fixed to the lugs with spring bars and closed with a buckle or a clasp.
- Clasp
- The fastening on a bracelet. A folding (fold-over) clasp has blades that fold flat under a cover; some have a safety catch. Check that it locks firmly.
Movement
- Movement
- The mechanism inside the case that keeps time and drives the hands. Watchmakers also call it the calibre.
- Calibre
- A maker's name or number for a particular movement design, for example Seiko calibre 2906. It is often engraved on the case back or the movement.
- Quartz movement
- A battery-powered movement that counts the vibrations of a small quartz crystal, usually 32,768 a second, and moves the seconds hand in steps.
- Mechanical (hand-wound) movement
- A movement powered by a coiled mainspring that you wind with the crown. A balance wheel swinging to and fro lets the energy out in even steps.
- Automatic (self-winding) movement
- A mechanical movement with a rotor that winds the mainspring as you move your wrist. Many can also be wound by hand.
- Rotor
- The half-moon weight in an automatic movement that turns with wrist movement to wind the mainspring. Seeing one through a case back is a clue to self-winding, not proof by itself.
- Mainspring
- The coiled spring that stores the energy of a mechanical watch.
- Balance wheel
- The wheel that swings back and forth at a steady rate and governs how fast a mechanical watch runs. Many vintage watches beat 5 times a second; Seiko's Hi-Beat calibres beat 8 times a second (28,800 beats an hour).
- Jewels
- Tiny synthetic rubies used as bearings in a mechanical movement to reduce friction and wear. '17 jewels' on a dial counts them.
- Stop-seconds (hacking)
- A feature that stops the seconds hand when the crown is pulled out to set the time, so a watch can be set to the second. It is not a fault.
- Keyless works
- The parts that let the crown wind and set a watch. Before them, watches were wound and set with a separate key.
At the bench
- Loupe
- A small magnifier held close to the eye to see scratches, marks and small parts. It never touches the watch.
- Movement holder
- A fixture that holds a movement by its edge so both hands are free and the parts are not handled.
- Water resistance
- How well a case keeps water out, which only a pressure test can confirm. Words on a case back describe what the watch was built for when new, not its state today.