Hacking seconds is a feature that stops a watch’s seconds hand so the time can be set exactly. On a watch with it, pulling out the crown halts the whole movement. It matters to anyone who wants to set the time to the second.
How does hacking seconds work?
In most designs a brake lever presses lightly on the balance wheel so it can no longer swing. Sometimes the lever acts on the hairspring through an intermediate part instead. Because the balance is blocked, the gear train comes to a halt too. A less common design works the other way round. It locks a wheel in the gear train, often one close to the seconds wheel, and so stops the watch.
Does hacking seconds make a watch more accurate?
No. Hacking seconds is a way of setting the watch, not a sign that it keeps good time. It lets the wearer line the seconds hand up exactly. Hacking also matters at the bench. Watchmakers rely on it when they test and adjust movements. Watches from Oris, IWC Schaffhausen and Rolex have the feature.
Where it comes from
Hacking movements became popular in the 20th century, when watches and timekeeping became more precise. Some watches go a step further with zero reset. On these, pulling the crown drops a hammer onto a heart cam, which sends the seconds hand back to zero. A. Lange & Söhne offered this in the Sax-0-Mat in 1997.
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