Demonstrating CFRP for high-precision, high-motion watch components

An R&D initative demonstrated CFRP for not only aesthetic watch parts, but structural and motion-sensitive components. Pictured (clockwise from top left): A retrograde module, minute hand holder, train bridge, movement and the machining of dial-side components from a CFRP laminate. Source (All Images) | Hirotaka Sugiyama

In the world of mechanical watchmaking, “in recent years, carbon fiber-reinforced plastic [CFRP] has begun to appear in watch cases and dials. However, its use has rarely been explored in horological micromechanisms [the tiny, intricate components in mechanical watches that perform the actual time measurement], where extremely strict requirements are imposed on dimensional accuracy, surface quality and long-term stability,” says Japan-based watchmaker Hirotaka Sugiyama.

Sugiyama embarked on a research initiative with the goal of exploring whether CFRP could be used as an alternative structural material to metals in these components within the movement portion of the watch.

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Why do this? According to Sugiyama, the primary reason was to see whether the stiffness of CFRP could be beneficial to the watch movement while maintaining structural stability.

“In addition, CFRP enables a modern, high-performance aesthetic that is not achievable with traditional metal movements. This project is an experimental and research-driven effort that challenges the conventional assumption that mechanical watch movements must be made exclusively from metal,” Sugiyama says.

The specialized watch components require precise machining and finishing before assembly.

For this study, CFRP was applied to the module plate, main plate, train wheel bridge and balance bridge components of the watch movement, along with the minute hand holder. A retrograde CFRP module with brass threaded inserts at screw fastening points was also incorporated to “ensure reliable and repeatable assembly without compromising the integrity of the composite structure. These components directly determine gear meshing positions, bearing alignment and the overall stability of the movement. While traditional watchmaking relies on metal alloys for these functions, this project investigates whether CFRP can fulfill an equivalent structural role through appropriate design and machining,” Sugiyama says.

The only movement component not manufactured in CFRP for this project was the pallet bridge — which covers and protects a crucial, oscillating lever within the watch —  as it is subjected to repeated impact loads and risked too much surface degradation to be included at this stage.

The CFRP components were designed using Autodesk (San Rafael, Calif., U.S.) CAD software. For each, 100 × 250-millimeter, 2-millimeter-thick plates were laminated from Toray (Tokyo, Japan) T300 carbon fiber/epoxy prepreg, and then machined to shape. A manual finishing process was used after machining “to improve dimensional accuracy and surface quality,” Sugiyama says.

“One of the most significant challenges in this project was the fine adjustment process required after rough cutting of the CFRP components. While precise dimensional tuning is essential after initial machining, CFRP behaves differently from metals and is prone to delamination along fiber boundaries. Fine adjustment also generates carbon dust, which poses a risk to movement performance. To address this, coarse material removal was first carried out using a sharp cutter, followed by fine adjustments with waterproof abrasive paper. These processes differ substantially from conventional metal finishing and require careful control to prevent fiber pull-out and surface damage.” Carbon dust management was also critically important throughout the process, and cleaning of CFRP parts was thoroughly performed before assembly.

The final parts were then ready to be assembled into the movement structures —  in a few cases, auxiliary parts and jigs were fabricated via 3D printing to support the assembly process.

After assembly and regulation, the completed movement achieved a daily rate of approximately ±2 seconds and a balance amplitude of approximately 280° — results which, Sugiyama reports, “confirm that properly designed and integrated CFRP structural components can deliver stable operation without compromising functional performance.”

“This case study demonstrates that when CFRP is approached not merely as a decorative material but as an engineering challenge, it can function as a viable structural material even in mechanical watch movements — one of the mechanical systems with the highest precision requirements in practical use.”

While the project is currently an independent watchmaking development and research effort with the parts in a prototype and validation stage, Sugiyama plans to ultimately release the watches in a limited small-batch offering. For more information, follow Sugiyama on Instagram or X.