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.

There are different techniques for performing this task, including using an inscribed cylinder where the wire rides in a precise groove and where a different material wire of specific thickness is inserted and wound beside the hairspring wire to provide the proper spacing as it ascends a cylinder.

Others see an assembly of specially formed disks (according to a patent from 1948 on behalf of Hamilton Watch Co.) that are stacked on an arbor with the hairspring wire to provide consistent and repeatable spacing.

Once the wire is held in position securely the process is the same as the standard spiral, heat treatment, and tempering for the appropriate material properties.

If done successfully, the helical hairspring has chronometric advantages over the flat spiral due to its ability to expand and contract perfectly concentrically and evenly. With a mounting position that keeps the helical spiral centered around the axis of rotation, this promotes isochronism, resulting in a very accurate and consistent rate.

This is why marine chronometers often sported helical hairsprings; the extreme accuracy was crucial for safety at sea. Historically, that is likely to be the largest application of the helical hairspring as now it is a rare novelty for high-end or high-tech movements.

These oscillators are seen so rarely that if you only know five watches with helical hairsprings you know a significant portion of the modern watches using them.

Out of all the “traditional” styles of hairsprings, the helical hairspring is my favorite since it adds so much three-dimensionality to the watch. And 2019 was a pretty good year for the helical hairspring as it was featured in multiple watches, reminding the WIS that we shouldn’t forget one of the pinnacles of historical watchmaking.

Taking that into consideration, here are my top five modern wristwatches sporting a helical hairspring in the hopes that brands will start incorporating them in the same way that nearly every brand that has created its own tourbillon model.

Take a look and see what you think of my favorites. Perhaps you have some different watches that get you excited about the elusive helical hairspring?

No. 5: Bovet Amadeo Fleurier Tourbillon Braveheart

Released in 2015, the Bovet Amadeo Fleurier Tourbillon Braveheart is a magnificent creation that highlights a lot of the ingenuity and finesse typical of Bovet. Its dual-sided tourbillon displays the running seconds on both sides, with a direction change for the rear to make sure it’s running forward.

It has a time display on both sides as well, with one side utilizing a retrograde minute function while the other has a window into the miniature differential mechanism for the keyless works. It also has a massive 22 days’ worth of power reserve and a sweeping indication to display this information.

After all this the highlight still is the helical hairspring, which appears shorter than many others you may see, yet still has eight spirals for a compact yet super functional result. Adding this type of hairspring to a tourbillon is a step to making it perform better than a regular oscillator.

It is polished instead of being blued (a common appearance for helical hairsprings) and almost sneaks by you if you aren’t paying attention. At number five on my list, the Bovet Amadeo Fleurier Tourbillon Braveheart is an incredible opener for a collection like this.

Further reading: The Bovet Amadeo Fleurier BraveHeart: Two Brave Hearts Are Better Than One.

Quick Facts Bovet Amadeo Fleurier Braveheart
Case: 45.2 x 16.2 mm, white gold, red gold, and platinum
Movement: manually wound Caliber 17BM02AI22J
Functions: hours, minutes (retrograde), double co-axial seconds; power reserve indication
Limited: 30 pieces in white gold or red gold; 20 pieces in platinum
Price: $557,700 (red gold); $632,500 / $646,600 (red gold with various degrees of diamond setting); $569,200 (white gold); $1,161,500 (platinum with diamond setting); all prices listed here do not include applicable sales tax

No. 4: Alchemists Cu29

One of my favorite pieces from 2019 – which also was one of my biggest cringes – was the Alchemists Cu29. This was a brilliant watch with unique architecture, incredible finishing, and a style that clearly stands out among competitors.

Its reliance on a marketing angle about the purported health benefits of its case metal did rub me the wrong way, but barring that issue I love this watch.

And any unique architecture deserves a unique oscillator, and this delivered. It has a blued helical hairspring with nine spirals, clearly on display thanks to a massively domed crystal. The stance of the balance, seemingly suspended over the dial, adds to the visual feast and makes this an awesomazing example of a helical hairspring done right.

Further reading: Alchemists Cu29: A Great Watch Overshadowed By Woo?

Quick Facts Alchemists Cu29
Case: 44 x 15.4 mm, patented Cuprum 479, a copper, silver, and gold alloy
Movement: manually wound Caliber 003 with suspended balance on a cylindrical hairspring, 3 Hz/21,600 vph frequency
Functions: hours, minutes, seconds; power reserve, function selector
Price: CHF 198,000

No. 3: Jaeger-LeCoultre Gyrotourbillon 2

I don’t think it’s possible to talk about helical hairsprings without talking about Jaeger-LeCoultre. This brand practically revived the practice of uniquely shaped hairsprings by launching multiple watches with helical hairsprings and one with a spherical (talk about a mind-bender of a spring).

The Jaeger-LeCoultre Gyrotourbillon 2 is easily on my list of top 20 watches of all time, especially considering it is in the iconic Reverso format.

The double-axis Gyrotourbillon is not only a feat of engineering, but also features at its heart a beautiful helical hairspring. Watching the assembly tumbling over and over is mesmerizing, and seeing the hypnotic breathing of the hairspring lets you know this watch is going to be accurate.

The watch may be considered an icon of modern haute horlogerie, and given the inclusion of the rare hairspring (which wasn’t included in the Gyrotourbillon 1 of 2004) it was a fantastic evolution for the Gyrotourbillon concept.

Further reading: Beautiful Contrasts: Jaeger-LeCoultre Reverso Gyrotourbillon 2.

Quick Facts Jaeger-LeCoultre Gyrotourbillon 2
Case: 36 x 55 x 15.8 mm, platinum or pink gold
Movement: manually wound Jaeger-LeCoultre Caliber 174 with double-axis tourbillon and cylindrical balance spring
Functions: hours, minutes, seconds; 24-hour indication, power reserve
Limitation: 75 in platinum and 75 in pink gold
Price: €266,000

No. 2: MB&F Legacy Machine Thunderdome

The newest bad boy on the block, the MB&F Thunderdome came out swinging for the title of most audacious triple-axis tourbillon.

As it is the fastest triple-axis tourbillon in the world with the only spherical balance in existence (as far as I know in a wristwatch), all suspended over the dial with a giant dome for easy viewing, the Thunderdome is strong contender for one of the coolest watches ever from the brand (and that is saying a whole heck of a lot).

Of course, with all the cool details it contains, it is the helical hairspring that has brought us here today. Inside the spherical balance is a large polished helical hairspring beating at a relatively normal 3 Hz (21,600 vph), and thanks to the use of a Potter escapement the rotational speed of the tourbillon is impressive to say the least.

The mechanism is awesome regardless of what the watch looks like, but when combined with the Legacy Machine’s good looks, it is hard to not rank this watch as one of the best helical hairspring examples ever!

Further reading: MB&F Legacy Machine Thunderdome: The World’s Fastest Triple-Axis Tourbillon – You Can’t Miss It! (Plus Videos).

Quick Facts MB&F LM Thunderdome
Case: 44 x 22.2 mm, platinum or tantalum
Movement: manually wound Thunderdome caliber with TriAx triple-axis tourbillon revolving at 8, 12 and 20 seconds; triple spring barrels, 45-hour power reserve, 3 Hz/21,600 vph frequency, 413 components
Functions: hours, minutes; power reserve
Limitation: 33 pieces in platinum with light blue guilloche dial; 10 pieces in tantalum for The Hour Glass, 5 with aventurine dial and 5 with dark blue guilloche dial
Price: CHF 270,000

N0. 1: Jaeger-LeCoultre Duomètre Sphérotourbillon

And yet I will always come back to one of my favorite all-time watches: the Jaeger-LeCoultre Duomètre Sphérotourbillon.

While it is less visually impressive (when dealing with groups of the most impressive mechanics ever) than the Thunderdome, the spinning top-style of the Sphérotourbillon has always captured my heart. Of the complete JLC collection, the Duomètre styling is at the top of my favorites list for the brand.

At the center of the Sphérotourbillon is what looks like a towering helical hairspring thanks to the tourbillon cage design. The tourbillon rotates and rolls on an angle of 15 degrees within an opening in the movement to highlight the mechanism.

When you combine this awesome implementation of the helical hairspring with the fact that the Duomètre Sphérotourbillon also features a second time zone, flyback seconds, dual power reserve displays, and very cool inset date ring, this piece enters into a realm of horological awesomeness and functionality that most others on this list lack entirely.

All of these watches are fantastic, and I would have a truly hard time choosing if I was told I could only have one, but when it comes to design, practicality, and engineering, the Jaeger-LeCoultre Duomètre Sphérotourbillon stands apart from the crowd!

So what did you think of my favorites? Would you agree these are some of the best manifestations of the helical hairspring or did I miss one? Share your thoughts on your favorite watch with a helical hairspring in the comments below.

Further reading: Precession Obsession: Jaeger-LeCoultre Duomètre Sphérotourbillon Moon.

Quick Facts Jaeger-LeCoultre Duomètre Sphérotourbillon Moon
Case: 42 x 14.3 mm, platinum
Movement: manually wound Caliber 389 with dual-wing architecture and bi-axial tourbillon inclined 20 degrees
Functions: hours, minutes, flyback seconds; moon phase, 24-hour display, dual power reserve indications
Limitation: 75 pieces
Price: €225,000

* This article was first published on February 2, 2020 at My Top 5 Favorite Watches With Helical Hairsprings.

You may also enjoy:

Bovet Amadeo Fleurier BraveHeart: Two Brave Hearts Are Better Than One

Alchemists Cu29: A Great Watch Overshadowed By Woo?

Beautiful Contrasts: Jaeger-LeCoultre Reverso Gyrotourbillon 2

MB&F Legacy Machine Thunderdome: The World’s Fastest Triple-Axis Tourbillon – You Can’t Miss It! (Plus Videos)

Precession Obsession: Jaeger-LeCoultre Duomètre Sphérotourbillon Moon

The Top-Secret World Of Bovet Hairsprings (Video)

Hairsprings: Origins, Progress, And (Dare I Say) Exciting Future