What Happens When You Pull the Crown: The Keyless Works Explained

Everything you ever do to a mechanical watch, you do through one small knurled knob on the side of the case. Turn it and the watch winds. Pull it and turn it and the hands move. On the Miyota 82S0, pull it and the seconds hand stops. The crown is the only part of the movement you touch, and behind it is a mechanism most owners never think about, which has to do three different jobs with one input and must never confuse them. Watchmakers call it the keyless works. This is the sixth article in our How It Works series.

Why keyless

For most of watchmaking history, watches were wound and set with a separate key, like a clock. Keys were lost, keyholes let in dust, and a slip of the key scratched the dial. In 1844 a young French watchmaker named Adrien Philippe showed a watch at the Paris Industrial Exposition that could be wound and set by a crown on the pendant alone, took a bronze medal, and patented the system in 1845. That same year Antoine Norbert de Patek, impressed, took him into partnership, and the company became Patek Philippe. Breguet had experimented with keyless winding decades earlier, but Philippe made it practical, and his layout of a stem carrying a sliding pinion, a setting lever and a spring to hold the positions is, in its essentials, still what is inside your watch.

The parts

Turn the 82S0 dial-side up and look at the edge where the crown enters. The winding stem is the steel shaft the crown screws onto. Riding on it is the sliding pinion, sometimes called the clutch or castle wheel, a small toothed sleeve that can move along the stem but must always turn with it, because the stem has a square section where the pinion sits. Next to it is the winding pinion, which turns freely on the stem and meshes with the crown wheel, which in turn drives the ratchet wheel on the barrel arbor. A small sprung pawl called the click lets the ratchet wheel turn one way and holds it against the other, which is the sound and feel of winding.

On the other side, controlling all this, is the setting lever, a flat steel piece with a pin that sits in a groove on the stem, and the yoke, a lever that pushes the sliding pinion along the stem. A spring, the setting lever spring or jumper, has notches that the lever clicks into, which is why the crown snaps into positions rather than sliding freely.

Position one: winding

With the crown pushed in, the yoke holds the sliding pinion against the winding pinion. Their teeth are cut as a ratchet, with sloped faces sometimes called wolf's teeth: turn the crown one way and they lock together, so the stem drives the winding pinion, the crown wheel, the ratchet wheel and the barrel arbor, and the mainspring tightens; turn it the other way and the teeth slip over each other with a faint click. That is the whole winding train: crown to spring in four parts.

Position two: setting

Pull the crown. The pin on the setting lever rides out of one groove on the stem and into another, and as the lever swings it pushes the yoke, which slides the pinion along the stem away from the winding pinion and towards a different gear, the setting wheel. Now turning the crown turns the setting wheel, which turns the minute wheel, which turns the cannon pinion, the small tube that carries the minute hand, and through a twelve-to-one reduction called the motion works, the hour hand as well.

There is a subtlety here that catches everyone the first time they understand it. The cannon pinion sits on the centre-wheel arbor, which is part of the gear train driven by the mainspring. If it were fixed to that arbor, setting the hands would mean forcing the entire gear train, the escapement and the balance backwards. It is not fixed. It is a friction fit, tight enough that the train drives it and the hands move with the time, loose enough that your fingers on the crown can turn it independently while the train stays still. When a watch keeps ticking but the hands lag or stop, the cannon pinion has usually worn loose. Watchmakers tighten it with a tiny crimp.

Hacking

The 82S0 has one more thing in the setting position. When the setting lever swings, a small brake lever moves with it and touches the rim of the balance wheel, stopping it. The watch is now hacked: seconds hand stationary, ready to be set to a time signal. Push the crown in and the brake lifts, the balance restarts, and the seconds hand moves off from where you left it. Hacking does not stop the movement in any deeper sense; the mainspring is still wound and the train is still under tension. It only holds the balance. Early 8215-family movements did not hack; Miyota added it around 2019, and every 82S0 in our kits has it.

Three positions and a date

The 82S0 has no date, so its crown has two positions. Movements with a date usually have three: in for winding, halfway out for a quick-set that advances the date without moving the hands, and fully out for setting the time. Rolex's calibre 3035 of 1977 popularised this by simply cutting another notch in the setting lever spring, which is a good example of how much of watchmaking is a well-placed notch.

Dive watches add a screw-down crown, which threads into a tube on the case to seal it. The idea was patented by two Swiss watchmakers, Paul Perregaux and Georges Perret, in 1925; Hans Wilsdorf of Rolex bought the rights the following year, improved it with a clutch so the crown could be screwed down without winding the movement, and launched it as the Oyster. The story that Rolex invented the waterproof watch from nothing is, as the FHH's own journal puts it, a myth. Rolex bought a good idea and marketed it superbly.

What this means at the bench

You will meet the keyless works in the Calibre Learning Kit at the very start, because to take the movement out of its holder you must first remove the stem. On the 82S0 this means pressing a small release on the setting lever while gently pulling the crown; the lesson shows exactly where. Two rules. Never pull the crown to the setting position and then press the release, or the setting lever may be out of its groove when the stem comes free, which is how setting levers end up bent and stems end up stuck. And when refitting, push the stem home until you feel the lever's pin drop into its groove, then check that the crown clicks between positions and that winding and setting both work before you go further. A stem that has not seated properly can pull out again with the crown in your fingers, which is alarming but rarely serious if you have not forced it.

It is a small mechanism. It is also, once you see the sliding pinion move as you pull the crown, one of the most satisfying to understand, because it is the part of the watch that has been listening to you all along.

Common misunderstandings

Rolex did not invent the screw-down crown; Perregaux and Perret did, and Rolex bought it. Setting the hands does not drive the gear train backwards; the cannon pinion's friction fit decouples them. Hacking does not stop the movement, only the balance. And a crown that turns without winding is usually a slipped sliding pinion or a broken click, not a dead mainspring.

Sources and further reading

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