Montres KF Spirograph Sport Review

by May 3, 2020Limited Edition, Montres KF


Montres KF is a relatively young brand, however is already pushing horological boundaries.

Founded in 2016, they manufacture only 20 pieces per year – all calibers are designed and built in house.  Their newest release is the Spirograph Sport; a tourbillon which although clearly has chronometry at it’s heart, also shouts “I’m different” with it’s modern looks.

Various technical accomplishments have been achieved with the release of this watch; amongst them is a balance-stop function – this enables the wearer to stop the tourbillon carriage and its balance-wheel at any time, in order to view the inner workings of the caliber.

The man behind the brand, Karsten Fräßdorf, explains the concept behind the piece in more detail below:

As I am an absolute fan of the Chronometry, the Tourbillon function is for me one of the greatest! Thanks to this complication, you can constantly see and admire visually the escapement beside the opportunity to get closer to a very precious time for a mechanical watch.

Even better, on the Spirograph Sport, I have added a stop function mechanism that allows the wearer to stop the balance at any time. This collection is the result of several patents on the escapement itself as well as on the stop balance mechanism which are both completely new. Not to mention that all my KF calibers are fully developed, conceived and assembled in my workshop of La Chaux-de-Fonds, Switzerland. 

To conclude, my Tourbillon is not only a playful function that you can observe at any time but also a useful complication as you can stop the Tourbillon when needed to settle the time. On the top of it, all my watches are shock resistant up to 5,000 G. Therefore, we call them « daily complications ». 

All these criteria (precision, useful functions and resistance) are deeply linked into all my conceptions and are the roots of my work.

Montres KF Spirograph Sport

Montres KF Spirograph Sport

Face & case

The stainless steel case is 45mm and has both polished and brushed edges, which seems to accentuate the different angles of the case. 

Look closely at the bezel and you will see it is quite wide – it doesn’t cause any aesthetic issues, just something I noticed.  Inside the bezel, the sapphire crystal covers a blue dial with a white honeycomb pattern that is slightly 3D and raised from the surface.   The honeycomb decoration is a apparently a representation of the coat-of-arms of La Chaux-de-Fonds, where the watch is produced.  The words Karsten Fräßdorf can be seen in black text between 10 and 2 o’clock, with La Chaux-de-Fonds in slightly smaller font below.

Circling the edge of the dial and sitting slightly higher than the face, is a white area which features the minute markers – every 5 minutes is highlighted with an area elongated inwards, with luminova markers.  The end of these oblong markers appear to be connected by a piece of darker blue wire, however this is actually on the face itself, circling the large numbers.

The numbers are oversized and white, with an application of luminova and a very thin dark border.  The number 5, 6 and 7 are however missing.  The giant aperture showing off the 60 second tourbillon centre piece, gobbles up everything between the pivot point of the hands and the bezel, including the numbers 5, 6 and 7.  The bridge sits horizontally across the centre, also appearing quite oversized, but is only a skeletonised frame, so as not to obscure the tourbillon. 

The tourbillon is larger than usual – Karsten Fräßdorf has performed a little bit of horological wizardry to engineer certain adaptations which stabilise the tourbillon for both shock absorption and accuracy of timekeeping.  If you are interested in the technicalities, please read the Other Stuff section further down the page. 

The hands are quite wide, in stainless steel and spear shaped.  They have luminova in the centres of the spears.

From the side, the lugs are quite short and rather than being the traditional curved shape, they have a right angle from the case, followed by a bulbous curve. 

The crown is large with a deep knurle, which makes for easy use.  At the end of the crown, the brand’s KF logo can be clearly seen in black.

Turn the watch over and the drama continues through the sapphire crystal back.  The main plate also features the embossed 3D honeycomb pattern and the tourbillon aperture (and 2nd skeletonised bridge) is the same size as on the front, with the addition of a second opening above; not quite as big, but allowing more of the movement to be seen. 

One thing that stands out particularly is the symmetry, which is unusual to be seen on a case back, but is clearly by well conceived design.

The frame of the case back is fairly narrow, with multiple engraving around it, including the brand and model.

Montres KF Spirograph Sport Case Back

Montres KF Spirograph Sport Case Back


Manufactured in-house, the Calibre 440 is a hand wound movement, featuring a one-minute tourbillon with internal geared wheel and traditional sea chronometer inertia balance, which also has a double curved free-spring hairspring.

With 34 jewels and beating at 18,000 vph, the Spirgraph Sport actually has a 70 hour power reserve barrel with special Geneva centring system, however the power reserve has been reduced to 44 hours, by means of the “Maltese cross” stopwork mechanism, which guarantees a more stable driving force and improves accuracy, 

Additional features are the escapement wheel and anchor arbor with Incafix® cap jewels and a 5000 G shock-protected movement, with special protecting devices for the dial, main plate and winding stem.

Montres KF Spirograph Sport Crown

Montres KF Spirograph Sport Crown


The strap on the watch reviewed was dark, matt blue and made from alligator leather with matching coloured stitching.  Interestingly, rather than just a standard leather lining, the lining was also in blue alligator, but in the round softer scales.

Bear in mind this watch can be designed and configured to the purchaser’s configuration, so I expect any strap material would be possible.

Karsten Fräßdorf’s name can be clearly seen, engraved across the stainless steel buckle, which secures with a butterfly clasp.

Montres KF Spirograph Sport Strap & Buckle

Montres KF Spirograph Sport Strap & Buckle

Other stuff

We’re going all nerd now, so skip to the next section if you don’t like learning!

Although watchmaking has been part of his life for almost four decades, this whole idea began a few years ago for Karsten Fräßdorf, with the construction of the first rim-free balance-wheel.

Thermal coefficient (the expansion of certain components during temperature changes) is a major challenge for watchmakers, especially
when it impacts the main components of a watch – a temperature increase of a few degrees can cause the balance-wheel to expand outwards, which could potentially cause a loss of several seconds.  

“Self-compensating” balance-wheels have been used for the last few decades to substantially reduce this expansion-related phenomena, however this new construction makes it possible to take a step forward by creating a balance-wheel which is capable of providing compensation described as “auxiliary”.  This compensation, further reduces the impact linked to the thermal coefficient which can not be resolved by a traditional self-compensating balance-wheel.  This new balance-wheel is more resistant to shocks, as it is made from a non-magnetic steel, which can withstand an inertia of 85 gr/mm2 and has a hardness of up to 600 Vickers (roughly 4 x that of 316L stainless steel).  

How it works, is that the balance-wheel plate forms one arbor crossing through the centre of the balance-wheel, which allows the material to extend in the event of a temperature increase. This extension is contained
by a second arbor, which remains static – this means that when when the material expands, the force is redirected to the fixed arms.  Each arm is attached to the static arbor by a screwed pivot point, which enables the balance-wheel to move inwards.  The static arms can then accommodate and therefor influence the effective mass, allowing the watchmaker to work on the inertia related to the thermal coefficient.  This is called the “auxiliary compensation” principle. 

Opposite the static arms, two auxiliary classification weights adjust the variable weight of the balance-wheel – these compensate for the weight of the screws placed on the two static arms, so that the balance-wheel is neither too heavy nor too light. 

A third arbor, which sits perpendicular to the first, enables fine adjustments, as well as classification of the balance-wheel at 18,000 vibrations per hour.

The unique setup of these components allows manipulation of the thermal coefficient.  Usually set at the time of the balance-wheel being paired with its hairspring, in this case the balance-spring always takes control, allowing for no alterations or transformations – the balance-wheel is therefor left to deal with any naturally occurring fluctuations of time (including those induced by changes in temperature).

The balance-spring, which should ideally be in unison with the balance wheel, is also susceptible magnetic fields in our daily lives – the balance spring is made from a “Straumann” alloy, capable of withstanding magnetic fields up to 1,000 Gauss and is also equipped with both an external “Phillips” curve and an internal “Grossman” curve.  This new balance-and-spring assembly enables fine and sophisticated adjustment of the regulating organ, which means the watchmaker timer shapes the heart of the watch by reading and interpreting the most sensitive components.

Montres KF Spirograph Sport on the Wrist

Montres KF Spirograph Sport on the Wrist

Our verdict

The modern design and honeycomb pattern give the Spirograph Sport a very distinctive look, not to mention the massive tourbillon on show.  The back is just as impressive to look at too.

In Karsten Fräßdorf’s own admission, he describes the watch as “madness, mid-way between high-flying technicality and waking dreams”, which resonates with my eccentric side – I really do like it and the Spirograph Sport is my type of watch.

There is also something special about the fact everything from the colour of the dial, hands and Arabic numerals applied to the face are also left up to the purchaser’s choice, so no two pieces will likely ever be the same.

Branded a sports watch, it certainly does look more sporty than most tourbillon watches out there, but I do think it could be just as well worn with more dressy attire.  At just shy of 14mm, it is quite deep, but the smooth edges will likely mean fitting beneath cuffs should be fairly painless.

The Spirograph Sport is available in a limited edition of just 10 pieces, with a price tag of 95,000 CHF.  It is a pity, but you will likely only see one of these if you buy one, or happen to be mingling in the right places at the right time!

I am genuinely intrigued to find out what is coming next from Montres KF.