Watchmaker’s Bench: What Makes It Tick? (Part 3) – Keyless Works and the Hand Setting Mechanism

The keyless works get its name from the fact that one does not need a key to wind or set a watch. Before the introduction of the keyless works, however, this was exactly how it was done. As we all know, the vast majority of watches today are wound and set via the crown/winding stem, and when we wind the watch or pull the crown out to set the time, we are engaging the keyless works.

In the final part of our series, What Makes It Tick?, we will look at each aspect of the keyless works and the hand setting mechanism in detail. For Part 1 of our series, which focused on the wheel train, click here, and for Part 2, which focused on the escapement, click here.

Winding Mechanism – Stem, Winding, and Sliding Pinion

The crown of a watch is connected to what’s known as a winding stem. This is a shaft that the crown threads into, and it’s the interface between the inside and the outside of a watch. The winding stem is made up of many different surfaces, all integral to its many functional purposes. We have clylindrical pivots, a square section, cut outs for posts to engage, and a threaded section for where the crown attaches.

Next, let us look at the winding pinion and sliding pinion. The winding and sliding pinions slide on to the winding stem. These two small wheels engage each other to ensure that the mainspring can be wound. The winding pinion is seated on a cylindrical section of the winding stem, and the sliding pinion is seated on the square. The winding pinion can rotate freely but the sliding pinion is fixed. The two pinions engage each other via teeth that act as a clutch. When the crown is wound anti-clockwise, the winding pinion can spin freely, and it does not engage any gears. But when it is wound clockwise, the sliding pinion engages with the teeth of the winding pinion so that it can then interact with the wheels that wind the mainspring.

Ratchet and Crown Wheels

The winding pinion has teeth on its outer surface that engage with the crown wheel. The crown wheel then interacts with the ratchet wheel. The ratchet wheel sits on top of the barrel (on the movement side) and is affixed via a screw. The crown wheel sits next to the ratchet wheel and acts as an intermediary between the winding pinion and ratchet wheel.

The mainspring coiled inside the barrel is connected to a small metal arbor via a hook. The ratchet wheel and screw are connected to the barrel arbor, so the mainspring gets wound when the ratchet wheel is turned.

Fun fact: you can directly wind the mainspring by turning that screw with a screwdriver.

Setting the Hands

When the crown is pulled away from the case to the time-setting position, a whole different series of wheels and pinions are engaged. In this position, turning the crown no longer winds the watch, but instead moves the hands so one can set the time.

Sliding Pinion Intermediate and Minute Wheels

With the winding pinion disengaged from the sliding pinion the watch will not wind. The sliding pinion slides forward and engages with another small pinion. That small pinion then engages with yet another pinion, and that pinion then engages with the minute wheel. The minute wheel features a large, toothed base and it has a small pinion mounted concentrically. The toothed base engages the cannon pinion and the small mounted pinion engages the hour wheel.

Cannon Pinion and Hour Wheel

The cannon pinion is what the minute hand of the watch is directly connected to and the hour wheel is what the hour hand is directly connected to. The cannon pinion is like a sleeve, and that sleeve slides onto the shaft of the great wheel of the watch and is held in place by friction. This friction needs to be very precisely set. If the friction is insufficient, the hands could flop around the dial after a knock or simply from gravity. If the friction is too great, however, then time-setting would be difficult. It would cause the wheels in the gear train to be forced forward, which would effectively increase the amplitude and cause the watch to run extremely fast whilst being set. This could cause serious damage to the movement. Ultimately, if the friction is set just so the cannon pinion will slide smoothly around the shaft of the great wheel, the watch will keep time as normal, and it won’t interfere with hacking.

The great wheel, which I wrote about in the previous installment of this series, rotates once every hour, and as a result, the minute hand turns once every hour. The hour wheel then sits loosely on top of the cannon pinion and is geared to rotate once every 12 hours.

With the hands properly set, the crown can then be pushed back into the winding position, which will disengage its ability to set the time. This will allow the gear train to take over the advancement of the hands. And that’s how that all works.

In concluding this series, we have examined how a simple mechanical watch functions. We haven’t delved into any complications such the automatic work, the calendar, or a chronograph—which are all more complex in nature— but you’re now equipped with a deeper understanding of how a mechanical timekeeper operates.

Featured image via ATG Vintage Watches