Credits: Article and images by Joshua Munchow @ Quill & Pad. See the original article here - https://quillandpad.com/2024/03/03/my-top-5-favorite-watches-with-helical-hairsprings-2/
The hairspring: the devilishly complex yet stunningly simple heart of a mechanical watch.
The hairspring is a notoriously difficult component to manufacture, especially consistently, so only a handful of companies have the capability to make them, and one (Nivarox, owned by the Swatch Group) still accounts for a (slowly shrinking) majority of all hairsprings made every year.
In the last two decades, a few independent brands have started making their own, often by hand, for the relatively small amount of watches they make, but most are still produced industrially in larger quantities.
Interestingly, almost all of the hairsprings made follow nearly the same form factor as well, meaning that the balance assemblies are closely related in design and function. But sometimes, from some manufacturers, the choice to go with something a little different for a particularly special watch entices engineers enough to move up the ladder into the even more complex world of helical hairsprings.
Helical hairsprings, also known as cylindrical hairsprings, are made similarly to the process for making a basic hairspring by hand but with one big difference. To make the basic hairspring, the thin spring wire is inserted into a mandrel (usually four at a time at 90-degree angles to each other) and carefully wound in a flat jig to completely coil the four strands of wire.
The entire jig is then heat treated and tempered to achieve the correct material properties for a hairspring and set the metal in the appropriate shape.
The springs are then separated into the individual springs, all now perfectly spiraled with a gap the width of the other three hairspring thicknesses, providing a consistent tolerance for the entirety of the spiral.
That handy trick isn’t possible with a helical hairspring as it is consistent in diameter along its length, but the spacing between the wire is not the same as a multiple of the wire thickness. For this reason, a custom-formed mandrel needs to be used, allowing only one helical hairspring to be formed at a time.
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Credits: Article and images by Joshua Munchow @ Quill & Pad. See the original article here - https://quillandpad.com/2024/03/03/my-top-5-favorite-watches-with-helical-hairsprings-2/