When watch collectors venture into the realm of high horology, some never really looked beyond aspects like brand recognition, avant-garde-ness or multi-complications of a timepiece. Today, appreciation for hand finishing is still not widely understood by collectors. Granted, high horology does not strictly necessitate hand finishing but the emphasis on craftsmanship has always been a part of traditional watchmaking. Although there are many things a machine can do better than a human (eg. CNC milling), certain finishing work can only be accomplished by a pair of skilled hands. And therein lies the charm of hand finishing – the precious “character” or “emotion” bestowed upon a timepiece through the blood, sweat and tears of an artisan.
As I delved deeper into haute horlogerie, specifically the independent watchmakers, there is something similar that struck me regarding a few interesting individuals’ fundamental approach towards hand finishing and basic chronometry. Perhaps “interesting” is an understatement after all. As a matter of fact, most of them (eg. Philippe Dufour, Kari Voutilainen, Laurent Ferrier, and perhaps Aaron Becsei) are grandmaster watchmakers who produce arguably the most exquisitely hand finished movements on this planet, period. In this article, I would be sharing this common set of, let’s just call it “philosophical modus operandi” (or PMO in short) that I have observed.
Perfectly Polished Convex Bevels
Bevelling (“Anglage” in french), is the process of chamfering the edges of a movement part, especially the bridges. This process was traditionally meant to remove burrs and combat corrosion.
Performed at the highest level, this technique produces clean, consistent, and highly polished convex bevels with no traces of machining marks. A convex bevel (as opposed to a flat bevel) is more difficult and more time consuming to produce, looks more refined and allows light reflection in various kinds of angles.
For delicate or hard to reach areas, the bevelling is meticulously done with a metal hand-file and finished manually with a piece of pegwood (with abrasive paste applied). Otherwise, a bench-style grinding wheel (made of either wood or leather) or a hand-held rotary tool called a “touret” would be used.
Sharp Inward Angles
This is probably the absolute telltale sign that a bevel on a movement is manually hand-finished – sharp inward angles. Because of the tight geometry, no rotary tool is able to properly chamfer and polish a sharp inward bevel without ruining that pointy angle.
Stroke by stroke, the artisan would use a metal hand-file and pegwood to create a beautifully polished inward angle. A high level of patience and dexterity is required to perfect this technique.
Black Polished Components
Black polishing (“Poli Noir” in french), also called mirror polishing, is the highest standard of polishing technique applied on movement parts (typically on steel surfaces).
Interestingly, the finishing only reflects light in a certain angle. At any other angles, the finishing appears black. And hence the name “black” polishing.
This is yet another technique that requires skilled hands and is painfully time consuming. The finishing is done on abrasive surfaces of different grits (eg. emery paper). The artisan polishes the movement part by moving it in a figure-of-eight or a circular motion on the abrasive surface, progressing from coarse to finer grits until a mirror shine is finally achieved. Sounds easy eh? Thing is if the artisan messes up at a grit, he/she would have to go back to the previous grits to start again!
As with all kinds of polishing job, overdoing it will cause substantial shape and material loss, while underplaying it will never get you the desired results.
Use of Overcoil Hairspring
Ever since the very first mechanical watches made, isochronism has always been a challenge in chronometry. Isochronism is the ability to keep accurate time even as the mainspring loses torque while it reaches the tail end of its power delivery. Short of using exotic methods like remontoire or a fusee and chain, a basic way to help in isochronism is via the employment of an overcoil hairspring in the escapement. Named after the inventor, it is often called a Breguet Overcoil.
Besides aiding in isochronism, an overcoil hairspring also improves timekeeping by minimising positional variation with its concentric “breathing” motion. This concentric “breathing” is achieved by shaping the outer terminal curve of the hairspring over and above the main coil before terminating it near the centre of the coil.
Despite its merits, there are some reasons why an overcoil hairspring is not so commonly used. Reasons like the addition of thickness to a movement, susceptibility to snagging, and being laborious to produce (an overcoil is bent by hand and subsequently requires careful adjustments). This is why overcoil hairsprings are only used in the higher end models of mainstream HH brands like Vacheron Constantin, Patek Philippe and A. Lange & Sohne.
Use of Free-sprung Balance
In a mechanical escapement, the balance wheel is typically either index-regulated or free-sprung. Instead of having a regulating index that varies the effective length of the hairspring, the free-sprung balance has a fixed-length hairspring and uses variable-inertia screws or weights for timing adjustments. Picture a spinning figure skater – as she pulls her hands/legs nearer to her body, she spins even faster.
I remembered during one of the PuristS interview with Philippe Dufour, he described, in his own words, the importance of a free-sprung balance:
“I use a freesprung balance. It’s not just for fun; it’s because I think it’s much better in the long term. Because the regulator pins, everybody knows it gives you problems. You make a nice adjustment today, between the flat and the vertical is nice, fifteen days later, you check it, it is different. Why? That’s why I threw away the regulator pins in my watches.” – Philippe Dufour.
Skin in the Game
After babbling so much about the common PMO from the few Independents, I bet you readers must be wondering if I have my “skin in the game”.
I’m glad to say I actually dipped my skin into the game. Well, sort of, but it is neither Independent nor Swiss. The timepiece that I have is the A. Lange & Sohne 1815 Chronograph (Ref. 402.032) in pink gold. It may not be from a low production independent watchmaker (sorry to disappoint you Indie fans!), but what the L951.5 movement entails is the same PMO exhibited in the timepieces from the independent watchmakers discussed above.
I have since declared this my “exit” watch, but let’s leave this story for another day. In the meantime, like many WIS-es, I still dream of owning a grail piece from Philippe Dufour. Will I get there? Only time will tell.
Editor’s Note: James Tan posts on his own Instagram account as @Dufourism, and joins Deployant as a contributor with this maiden article. Dufourism. A captivating moniker to those in-the-know. Needless to say, James is a big fan of Dufour. Not the Rolex CEO, but the grandmaster watchmaker Philippe Dufour. Despite his refined taste for hand finished timepieces, he started out humbly like many other watch collectors with a Seiko 5 back in 2007. During his “me time”, he enjoys reading watch blogs as well as meeting and chatting with fellow watch lovers over a cup of coffee. Outside of watches, he is also a sartorial footwear enthusiast who digs dress shoes such as Edward Green, Vass and Crockett & Jones.
Yes, Galileo did discover that pendulums show approximately the same period for swings of differing lengths, (Huygens later recognized that it required the pendulum’s pivot to vary along a cycloid curve to achieve true isochronicity).
I can understand your point about varying side forces on the balance staff. I wonder if the overcoil has been measured for its improvement of isochronicity. That would be interesting. Thanks again!
Incidentally, in the same PuristS interview (http://www.thepurists.com/watch/features/interviews/dufour/) mentioned in my article, Philippe Dufour was asked about the importance of the overcoil hairspring. This was his reply:
“It’s a must, I mean if you want to make something accurate. It’s very simple to understand. You see on a projector for example a flat movement and you see how the hairspring goes one side and it’s stacked to the other end. The hairspring with a Breguet overcoil is breathing like a heart, expanding on every side. And it brings you of course a better result.” – Philippe Dufour.
I’m pretty sure Dufour didn’t exactly understood the physics behind an overcoil. He stuck to it because it worked for him in his many years of watchmaking.
I fully understand your frustration on the omission of Romain Gauthier (or anyone’s favourite watchmaker, for that matter) in my article. Truly, there is no need to “laugh” at the omission. First of all, my article is not intended to be a “Top 5 Best Watchmaker\Finisher in the World” or anything of that sort. In case you missed the point of my article, it is to share my observation on the common traits of a few traditional high-end watchmakers’ approach to hand finishing and basic chronometry.
Secondly, I’m sure you realised that Gauthier’s omission in my article is due to the non-use of an overcoil hairspring, which I’m certain is why you brought out the point on overcoils. I do agree that overcoils are not a product of haute horlogerie, but they do symbolize traditional watchmaking in one way or another. Again, my point in the article is not to say that overcoils are haute horlogerie, but rather to highlight their staunch use by that particular few watchmakers.
I don’t really believe that silicon is more isochronous than an overcoil hairspring.
The fact is, a flat spring (silicon or not) is easier to manufacture than an overcoil and requires less adjustment. Today, modern timepieces have mainsprings that produces more constant torque, have longer power reserve to give a longer “flat” torque curve, have automatic winding systems which kind of acts like a remontoire. It is all these that made overcoils “irrelevant”. And yet, overcoils are still being used today, although not as extensively as the past based on reasons provided above. So I guess, there is still a hint of practicality in their use, with Rolex as a fine example (yes 1 million of them as you’ve mentioned).
Having said that, I have no doubts at all that Romain Gauthier does fantastic hand finishing. The finishing on his Logical One is among the best in my opinion.
Nothing on Romain Gauthier, the best hand-finished movements out there? Laughable omission. Also, overcoils are not a product of haute horlogerie; Rolex uses them in 1 million watches per annum.
Also, silicon has largely made an overcoil irrelevant (just like the tourbillon) because the isochronism is so insignificant, as it is much more inert than traditional materials.
My understanding is that an overcoil hairspring helps in reducing positional variation, not isochronism. If it could do the latter, I’d love to know by what mechanism. Thanks.
Hi Aaron Abeloff,
I’m not sure if I can explain it well enough, but I’ll give it a try.
Galileo first discovered isochronism centuries ago when he was observing the swinging of a chandelier at the Cathedral of Pisa. He found that no matter how small the swing is, the time it took for each swing to complete was exactly the same. This is isochronism as displayed by an ideal oscillator (in this case, the chandelier). However, the “perfect oscillator” is not possible on a wristwatch due to factors like positional variance and fluctuating frictions on the balance pivot as the hairspring expands and contracts.
People keep saying that the “concentric” breathing of an overcoil helps in isochronism. But how?
As we know, a hairspring is anchored by two points in a balance wheel (one at the collet and one at the stud carrier). In a flat hairspring, the lateral thrust created by the uneven “breathing” motion generates a lot of varying friction on the balance pivot. Whereas in an overcoil hairspring, the “breathing” is much more concentric, making the lateral thrust on the balance pivot much less. And this in turn makes the oscillation more isochronous.