A. Lange & Söhne - Balancing Spring Production
WORLDTEMPUS - 19 July 2010
One of the reasons why so few companies make balance springs is that it is one of the most difficult components to master. Know-how and strict manufacturing practices must be applied. At A. Lange & Söhne, the process was devised and mastered by Lutz Großmann and Reiner Kocarek using a Nivarox Invar alloy sourced from a German supplier as a wire with a diameter of 0.5 mm as the basis. If the completed balance spring—which will measure about one-hundredth of the diameter of a human hair—is off by even one-thousandth of a millimeter, it could throw the watch's rate off by something like half an hour.
Kocarek explains, "The greatest problem surrounding the manufacture of balance springs is the incredible precision needed to achieve them."
Rolling, flattening, baking
The material is first drawn through a series of diamond dies to stretch them until the prescribed diameter of five-hundredths of a millimeter is achieved. The wire is then rolled—thereby flattening it—at a rate of ten meters per minute. "This is the hardest part of the whole process," Kocarek adds. The springs must be rolled within a tolerance of 100 nanometers.
Großmann chose the Breguet-style terminal curve for Lange's springs, which sees the terminal curve bent upward and then diagonally across the body of the bent hairspring, allowing it to concentrically "breathe." Then the springs are heated over night to harden them.
Finally, it is the way that the hairspring and balance wheel interact with each other—known as "pairing" to a watchmaker—that in the end defines whether it all works to equal a precise watch rate. Großmann therefore devised a machine that can measure the paired components in several positions before they are added to a movement: a laser that can scan the balance at work, counting the oscillations, measuring the amplitudes, and transmitting the data to a computer. This process "classifies" the springs, with A. Lange & Söhne now maintaining 20 different classifications.
Where it is used
A. Lange & Söhne's balance spring department is capable of making 1,000 springs per day. However, it doesn't—preferring to make only the amount actually needed. At the moment, only springs are made here that are used in A. Lange & Söhne's own calibers and in some by other Richemont group brands, such as Jaeger-LeCoultre. Both of these brands also use Nivarox balance springs where it makes better sense to do so. Eleven complicated Lange & Söhne watches are currently outfitted with the in-house balance spring.
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