In Japan, sleepers on bridge structures are securely fastened using a unique hooked bolt. When a train passes over the railway lines on a bridge, the sleeper gets compressed due to the train’s weight. If a regular bolt were used, it would lose all its tensile strength . However, the hooked shape bolt acts like a spring, flexing with the movement and maintaining sufficient tensile pull on the bolt , ensuring that the sleepers remain tightly attached to the bridge. Unfortunately, this significant movement in the hooked bolt can cause the nut to become loose.
To address this issue, our product, the HARDLOCK® Nut, has been effectively employed for over 20 years to secure these specific fasteners, preventing any potential loosening. Currently, it is used in more than 70% of these applications by East Japan Railway Company, a prominent passenger railway company in Japan and the largest among the seven Japan Railways Group companies, as well as many other renown companies.

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