The importance of the hairspring


Two types of spring

Typically, most watches contain two types of spring, the mainspring and the hairspring. In this feature, the focal point is the hairspring, however, in the interests of completeness, this article begins with explaining the difference between the two.



The mainspring sits within a spring barrel, effectively the fuel tank of the watch. A Zeitwinkel timepiece features an automatic movement where the mainspring is automatically tensioned, energised with the natural motion of the wearer’s wrist. In addition, the mainspring can be tensioned by manually rotating the crown.

The mainspring is designed to store sufficient energy to allow the watch to run autonomously for up to 72 hours. The energy stored within the barrel is transferred via the gear train to the escapement and regulating organ. The forces at play are significant and therefore must be carefully managed to ensure the watch runs precisely and reliably.




Unlike the mainspring, the hairspring is a more delicate soul. It is not subjected to the same extremes of force. The combination of the balance wheel and hairspring form what is commonly referred to as the ‘regulating organ’. It is this double act that precisely manages the impulse and unlocking sequence that ultimately controls the ‘flow of time’. The behaviour of the hairspring is critical to precise timekeeping.

Manufacturing hairsprings is very complicated. In this feature, the complexity of producing hairsprings is explained in detail.



Making hairsprings

All companies making hairsprings are tight-lipped when it comes to the specific composition of the alloy they use. However, the make-up of the metal must have certain characteristics. For example, the alloy must not be liable to corrosion nor must its behaviour be influenced by temperature.

The alloy is usually supplied on reels in a wire-like format and then passed over a number of rollers and through a series of dies. The objective of this process is to gradually reduce the thickness of the wire. This process is never rushed and usually takes place over a number of days. It is imperative that the thickness of the resultant wire should be uniform. Ultimately, it will measure just a few microns in diameter and be made to infinitesimal tolerances, 100 nanometers (0.0001mm) in magnitude. If the cross section of the wire fluctuates, the balance can never be effectively regulated and the watch will never deliver precision.

Once the alloy wire is the correct thickness it is cut into ‘blades’ and coiled prior to being cooked in a specialist oven. After the hairspring is made, it is paired with a balance wheel to form balance. It is subsequently poised and then regulated. The hairspring forms the heart of any fine timepiece and, as any romantic will attest, the value of this organ is almost priceless.


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