Origin of the HARDLOCK Nut

Over 50 years ago, Katsuhiko Wakabayashi (1933–2024) invented the HARDLOCK Nut and founded HARDLOCK Industry Co., Ltd. Originally, he had developed another locknut through a different company he had established. However, frequent complaints from users made him realize that the original product was imperfect, and he became concerned that it might one day cause a serious accident. For over a year, he tirelessly pondered the solution to the perfect locknut.

One day, while reflecting at a Shinto shrine, he noticed the wedge used in the shrine’s gate—a centuries-old Japanese construction technique known for its ability to seamlessly join parts while remaining easily removable.

Inspired by the wedge principle, Katsuhiko went on to invent the HARDLOCK Nut (HLN).

Self-locking Mechanism of the HARDLOCK Nut

The HARDLOCK Nut is comprised of two nuts. The Convex Nut (bottom nut) features a tapered eccentric protrusion, which acts as a wedge.

The Concave Nut (top nut) is designed with a tapered concentric recess that accommodates the eccentric protrusion of the Convex Nut.

Tightening the Convex Nut achieves the required preload in the bolted joint. In contrast, tightening the Concave Nut does not directly affect the preload but generates a strong locking load across the bolt shaft.

Due to the tapered wedge interface, as the Concave Nut is tightening over the Convex Nut, the threads of the Convex Nut are pushed against one side of the bolt by the Concave Nut, while the threads of the Concave Nut are pulled from the opposite side.

Advantages

In addition to its superior locking effect, the HARDLOCK Nut offers the following benefits:

  • Reusable: Reusable over 50 times with consistent performance.
  • Preload-Independent Locking: Maintains secure fastening, even with minimal or no preload.
  • Simple Installation: No special tools are required. Torque the Convex Nut to your specifications, and the Concave Nut to our recommendations.
  • Easy Preload Management: Installing the Concave Nut does not alter the preload established by the Convex Nut.
  • Customizable Options: Available in various sizes, materials, and surface treatments, with customization options.