Review: Audemars Piguet Royal Oak Openworked

In recent articles, we've explored some of the most amazing complications watchmaking has to offer, the most intricate and complex pieces of handmade micro engineering ever seen. This Royal Oak by Audemars Piguet, however, is not one of those watches. It doesn't have a tourbillon, a calendar or a minute repeater. It doesn't even have a date window. What it does have, however, is a movement that showcases one of the most impressive feats of watchmaking ever achieved.

It would be wonderful to tell you how this watch utilises a technique passed down through generations of watchmaking to make it more accurate, or more complex, or more practical, but that simply isn't true. What's happened here is that Audemars Piguet has taken a standard calibre 3120, and cut some bits out. Why? No reason, really, other than that it looks nice.

Clockmakers have been showing off their handiwork through the medium of skeletonisation—or 'openworking'—for centuries, right back to clockmaker André Charles Caron. As watchmaker to Louis XV from 1720 to 1760, it was all very well and good him telling the King that his work was worthy of the crown—better simply to show it. And so, he did, by cutting great big holes in the dial so the inner workings could be seen ticking away.

Audemars Piguet has been skeletonising watches since 1930

As an idea, it caught on, and the very best clock and watchmakers have skeletonised their crowning achievements ever since. It's a bold move, leaving nothing left to the imagination, nothing to hide behind, and gives a brand like Audemars Piguet the opportunity to show just how well made its movements really are. It's a practice Audemars Piguet has been executing since the 1930s, and it's keeping the tradition very much alive to this day.

What exactly does skeletonisation entail? Well, there's a great deal to keep on top of when it comes to putting a movement on such an extreme diet, because of course the plates and bridges getting trimmed serve a structural purpose. As well as sandwiching the wheels and pinions that transfer power across the watch, they also hold the jewels that keep friction against moving parts to a minimum. Then there's the setting lever, the balance, the mainspring barrel. Figuring out what's needed and what's not is tricky.

But it's not enough to simply hack away the areas that have been identified as superfluous to the operation of the movement. As the only purpose of this mechanical surgery is to make the watch look more appealing, leaving dirty great uneven holes all over the place would simply make the whole exercise moot. This may be Swiss, but it isn't cheese.

So, care and attention are taken to extract a design from the metal, to give pleasing uniformity and sense to the thin strips left behind. Wheels are exposed and framed to reveal the mechanical execution of the movement, treading a fine line between elegant intricacy and a squiggly mess. A decision needs to be made for every line, every angle, balancing the desire for beauty and the need for functionality. It's a chance for a watchmaker to really let their hair down.

It takes weeks of work to convert a calibre 3120 to a 3129

And it doesn't stop there. Skeletonised movements can be found in watches at a tenth of the price of this £60,000 flagship thanks to computer aided machining, and the results aren't half bad. But there's a tell, a pretty major one, that's revealed by the inadequacies of CNC machining. Take a look at any skeleton watch cheaper than this Royal Oak and something will become readily apparent once you know to look for it: all the inside angles are rounded off.

This is because the single-axis machines used to shape bridges and plates are limited by the diameter of the spinning bit used for the cutting. It's just not possible for milling machines like this to cut a sharp inside corner like you see here in this Royal Oak. The only way to do it is by hand. So, all the final shaping of this movement—christened 3129 following the skeletonisation procedure—is done with hand files of different shapes, sizes and angles once the rough shape is machined out.

And there are hundreds of angles to hand file here, hundreds. The process doesn't take hours, or even days—it takes weeks. I can only hope the artisans doing the work have a good series of podcasts to listen to or something, because hand-shaping this movement with tiny needle files seems like the very definition of tedious. One wrong move and it's in the bin.

But they're not out of the woods yet. The movement at this stage has its basic shape, but that's not good enough to withstand the scrutiny of the most discerning customer. The movement must be finished. Finishing here means to provide a final surface treatment for aesthetic reasons, although the motivations behind these finishes do have origins in practical logic.

Each angle is hand filed and polished to create the skeletonised look

The polished, chamfered edge, for example, is done by hand using files to shape the edge and graded applications of diamond paste to achieve the polished finish. A chamfer tool in a milling machine can replicate this shape to a degree, and some manufacturers use this as a first stage before final polishing, but those tricky inside edges here rule that technique out yet again.

The final result not only looks nice, it also removes the sharp edges of the movement, preventing small fragments of metal from breaking off and contaminating the moving parts, while the polished finish better resists oxidisation.

Then there's the graining, straight and circular. You won't be surprised at this point to find out that, for the Royal Oak, a machine has no part to play in this process. It's a finish that provides a pleasing contrast against the polished chamfers—all while providing channels to catch fine motes of metal worn away by the operation of the movement.

Straight graining may be a simpler process than many of the others used here—providing a nice, straight line can be achieved—but the circular graining mainly hidden within the nooks and crannies is applied circle by circle, continuing underneath the bridge and along the plate where it can no longer be seen.

Even the solid gold rotor weight has been pared down

In the cold, hard light of day, the skeletonisation of Audemars Piguet's calibre 3120 to turn it into a 3129 is needless. With no measure of improved performance, a negligible weight saving and the absence of additional functionality, it makes no reasonable sense why anyone would buy this watch over its less structurally fragile cousin.

No sense, except for an appreciation of the time, skill and perfectionism required to bring this level of mechanical beauty into fruition. You can't make something like this if you don't care about it, and every line, every angle, every mirrored surface reflects the passion of the watchmaker who gave it life. It may not be mechanically complex, but emotionally? It's the most intricate of all.

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