Bend, Don't Break: How TAG Heuer's Monaco Evergraph Replaced Levers with Flexures

A conventional automatic chronograph uses somewhere between 50 and 80 individual parts to manage its timing function. Column wheels, operating levers, coupling springs, hammer arms, return springs, heart cams, and their associated screws and pins all interact through pivots and sliding surfaces. Every pivot generates friction. Every spring fatigues over millions of cycles. Every sliding surface needs lubrication that eventually degrades.

TAG Heuer looked at that parts list and asked an unusual question: what if the chronograph mechanism did not pivot at all? What if, instead of levers rotating on jeweled posts, a single monolithic part simply bent into position and stayed there?

Announced at Watches and Wonders 2026 in Geneva, the Monaco Evergraph houses calibre TH80-00, developed over five years with Vaucher Manufacture Fleurier. Its signature innovation is a pair of compliant bistable mechanisms, fabricated from nickel-phosphorus using LIGA micro-fabrication, that handle start, stop, and reset without a single conventional pivot in the chronograph train. It is not a concept piece. Production is unlimited, and the watch is available now at $25,000.

What Compliant Mechanisms Actually Do

Compliant mechanisms transmit force through controlled elastic deformation rather than through hinges and joints. Instead of a rigid arm rotating around a pin, a flexible beam bends. The beam stores energy in its deformed shape and releases it when crossing a critical threshold. In engineering, this concept appears in everything from MEMS accelerometers in smartphones to deployable satellite antennas. In watchmaking, it is almost completely new.

A bistable compliant mechanism has two resting positions. It will stay in either position indefinitely without external force, much like a light switch. Pushing it past a central tipping point causes it to snap into the opposite stable state. That snap is fast, repeatable, and independent of how quickly or firmly the user applies force. Push the chronograph button gently or jab it hard, and the mechanism crosses the same threshold and lands in the same position.

For a chronograph, this behavior is useful in two places: engaging and disengaging the timing function (start/stop), and returning the elapsed-time hands to zero (reset). Traditional chronographs handle both tasks with multiple interconnected levers, each rotating on its own axis. Remove those axes, remove those levers, and you strip out the primary sources of wear in the entire complication.

Start, Stop: One Flexure

In the TH80-00, the start/stop function relies on a single nickel-phosphorus bistable blade positioned between the 2 o'clock pusher and the vertical clutch. When the pusher is depressed, a beak-shaped hammer rotates inward and slides along a protruding arm of the flexure. As force accumulates, the blade buckles past its central instability point and snaps into its second stable state, engaging the vertical clutch and connecting the chronograph seconds wheel to the going train. Press again, and the blade snaps back, disengaging the clutch and freezing the chronograph hand.

Because the blade's transition depends on reaching a critical buckling force rather than on lever geometry, actuation speed is essentially constant. TAG Heuer claims the engagement and disengagement times are identical regardless of button pressure, something that traditional column-wheel and cam-actuated chronographs cannot guarantee. Over hundreds of thousands of cycles, the nickel-phosphorus alloy operates well within its elastic range, and fatigue accumulation remains negligible at the stress levels involved.

Vertical clutch engagement itself is not new. Rolex's calibre 4130, launched in 2000, and many subsequent chronographs adopted vertical clutches because they eliminate the hand-jump artifact visible in horizontal clutch designs. What is new here is how the clutch gets told to engage. Removing the column wheel, its detent spring, and the operating lever that bridges button to wheel eliminates several precisely fitted parts and their associated lubrication points.

Reset: A Second Flexure

Resetting a chronograph is mechanically harder than starting or stopping it. Two heart-shaped cams, one on the chronograph seconds arbor and one on the minute counter, rotate at different speeds and sit at unpredictable angular positions when the user hits the reset pusher. A hammer must simultaneously contact both cams, push each past its high point, and force both hands back to twelve o'clock. If the hammer contacts one cam before the other, or if it lacks sufficient force to rotate a cam past its peak, the hand sticks at the wrong position.

Traditional solutions use either a pivoting hammer (simple but single-contact), a self-adjusting pivoting hammer (more complex, adds another pivot), or a linear hammer (moves in a straight line to contact both cams at once). Rolex's calibre 4130 uses a linear hammer with a self-adjusting arm for the central seconds cam. Frédéric Piguet's calibre 1185, the basis for several Audemars Piguet chronographs, used a rigid linear hammer that demanded extremely tight manufacturing tolerances.

TAG Heuer's reset flexure takes a different approach. A single nickel-phosphorus part with complex geometry contacts both heart cams simultaneously when forced past its bistable threshold by the 4 o'clock pusher. Because the flexure bends rather than pivots, it can distribute force across its contact surfaces with some self-adjustment built into the deformation profile. Manufacturing precision is still critical, but the tolerance chain is shorter because there are no intermediate pivots accumulating angular error.

LIGA: Printing Watches Like Chips

LIGA stands for Lithographie, Galvanoformung, Abformung: lithography, electroplating, and molding. It is a micro-fabrication process borrowed from semiconductor manufacturing that produces metal parts with vertical sidewalls, sub-micron surface finishes, and aspect ratios impossible to achieve with conventional machining or stamping.

Production begins with a thick photoresist layer applied to a conductive substrate. Ultraviolet light (or, in high-resolution variants, synchrotron X-ray radiation) exposes the resist through a mask carrying the part geometry. Exposed resist is dissolved, leaving a precise mold. Nickel-phosphorus is then electrodeposited into the mold cavities atom by atom, filling the voids with fully dense metal. After dissolving the remaining resist, the finished parts are released from the substrate.

Rolex uses LIGA to produce the anti-backlash center wheel in the Daytona's calibre 4130. Patek Philippe and other manufacturers use it for escape wheels and pallet forks. TAG Heuer's application is structurally different. Instead of gears or escapement components, the LIGA parts here are flexural elements whose function depends on precise control of cross-sectional geometry. A beam's stiffness scales with the cube of its thickness: a 10% error in thickness produces a 33% error in bending stiffness. LIGA's dimensional control, typically within a few micrometers, keeps the buckling force of each flexure within a tight enough window that every watch feels the same.

Nickel-Phosphorus as a Structural Material

Nickel-phosphorus alloys deposited by electroplating are amorphous (non-crystalline) when the phosphorus content exceeds roughly 10% by weight. Amorphous NiP has several properties that suit a flexural chronograph component. Its yield strength sits between 800 and 1,200 MPa depending on heat treatment, placing it comfortably above the stresses generated during bistable snapping. It is non-magnetic, eliminating interaction with the movement's balance and hairspring. And its fatigue endurance limit in the elastic regime is high relative to crystalline nickel alloys, because grain boundaries, the nucleation sites for fatigue cracks in crystalline metals, do not exist in the amorphous structure.

NiP is also self-lubricating at micro-contact scales. Its surface hardness after moderate heat treatment reaches roughly 700 HV, and its low surface energy reduces adhesive interactions at contact points. For a flexure that never actually slides against another surface (it bends in place), even this is somewhat academic. But where the pusher interface transmits force into the flexure's protruding arm, a low-friction surface reduces wear at the one contact point that does exist.

Inside the TH80-00

Beyond the compliant chronograph mechanism, calibre TH80-00 runs at 5 Hz (36,000 vibrations per hour), matching the frequency of Zenith's El Primero and Rolex's calibre 4130. Higher frequency improves timekeeping stability and provides natural 1/10th-second chronograph resolution, since the seconds hand advances in discrete steps of 0.1 seconds.

TAG Heuer fits the movement with its TH-Carbonspring balance, a carbon-composite hairspring developed in-house. Carbon hairsprings are antimagnetic, thermally stable, and lighter than conventional Nivarox alloys. Combined with the COSC chronometer certification (achieved by the fully assembled movement, not just the bare calibre), the Evergraph meets daily accuracy standards of -4/+6 seconds.

Power reserve reaches 70 hours from a single mainspring barrel, respectable for a 5 Hz automatic chronograph. The movement architecture is inverted, placing the barrel, gear train, and balance on the dial side behind a transparent sapphire plate. Arched bridges spanning the barrel and escapement provide structural rigidity while allowing a full view of the mechanism from the front. A checkerboard finish on the rear plates nods to the Monaco's racing heritage without compromising legibility of the technical layout.

Case dimensions are 40 mm square and 14.5 mm thick in grade 5 titanium, available in natural brushed finish or black DLC coating. Water resistance reaches 100 meters. The crown sits at 9 o'clock, preserving the original 1969 Monaco layout, with chronograph pushers on the right at 2 and 4 o'clock.

Why It Matters Beyond One Watch

Compliant mechanisms are standard practice in micro-electromechanical systems, precision instruments, and medical devices. Watchmaking has been slow to adopt them because the Swiss industry's manufacturing infrastructure is optimized for turned, milled, and stamped parts assembled on jeweled pivots. LIGA production requires photolithographic equipment and electroplating baths, not Swiss-type lathes and Schaublin mills.

TAG Heuer's decision to ship this technology in an unlimited-production, commercially priced watch signals that LIGA-fabricated compliant parts have crossed the threshold from laboratory curiosity to industrial viability. If the Evergraph's reliability data over the next several years confirms the theoretical advantages of zero-pivot chronograph actuation, other manufacturers will likely follow. Compliant start/stop mechanisms could simplify movements, reduce assembly time, and extend service intervals across the price spectrum.

That outcome is not guaranteed. Compliant mechanisms in MEMS devices operate in controlled environments. A wristwatch endures shocks, temperature swings, and years of continuous vibration. Long-term fatigue behavior of LIGA-deposited NiP under real-world wrist conditions has limited published data. TAG Heuer is, in effect, running a fleet-scale materials experiment on thousands of paying customers. Given the company's recent track record with the TH-Carbonspring and its lineage of technically ambitious research platforms, that bet seems calculated rather than reckless.