The kapsel is an essential element for the proper functioning of Viennese action. Despite its apparent simplicity, it must be crafted with extreme precision to ensure optimal performance.

The first percussion instruments of the German school featured wooden kapseln, but the leading Viennese fortepiano makers soon began using brass models, likely crafted by small workshops specializing in metalworking. Even today, industrial mass production of these parts does not exist, given the low demand: for this reason, artisanal production remains the preferred choice of the most attentive and scrupulous makers.

Four fundamental aspects determine the quality of a good kapsel:

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1. BRASS

For my kapseln, I use CW508L brass, with a lead content of less than 0.05%. This ensures a perfect seal between the fork and the axle, preventing adjustment losses. There are many brass alloys on the market, but the one I use—thoroughly tested—is the only one that ensures optimal workmanship and long life. Although we don’t know the precise composition of historical alloys, practical analysis shows that old forks have a notable “spring effect,” a sign of a low percentage of copper and the absence of lead, ideal for withstanding the tension of adjustment.

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2. THE STEEL AXEL 

Inside the fork, the two small punches visible from the outside are the fulcrum of the Viennese action. This critical point connects the fork to the hammer, transforming the pressure of the key into the necessary counterblow. Once the position and depth are determined, the housing is manually finished to ensure a perfect seal for the steel axle. The angle is calculated to minimize friction between the axle and the brass of the fork.

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3. THE RIVET

Riveting is the process that joins the threaded shank to the fork. The combination of a square hole and a riveted shank ensures durability and stability over time, preventing rotation or wobbling even after decades of use. By avoiding welding, this traditional cold-melting method remains the best because it avoids overheating the brass of the fork and preserves its mechanical properties.

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4. THREADING

The shank threading is made with traditional dies with a fine pitch for more precise adjustment