Structure for strong and close fit that prevents loosening due to vibration or impact!FUJI SEISAKUSHO , Co.,Ltd


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Fuji Double Lock Nut uses a close fit between two concave and convex nuts to prevent looseness

Product Name = Fuji Double Lock Nut

The powerful looseness prevention effect protects infrastructure

Fuji Double Lock Nut uses an eccentric* structure to prevent looseness due to impact or vibration. A concave top nut and a convex bottom nut are included in one set. The nuts can be easily attached with a single wrench.

Loose screws can cause serious safety problems in many structures and equipment. Furthermore, even if loose screws do not result in safety problems, they will lead to problems such as equipment failure and extra cost due to frequent maintenance.

In accordance with United States Federal Aviation Standards, the double lock nut does not loosen even in a NAS-type vibration test that applies 1,800 vibrations per minute for 17 minutes, for a total of 30,000 vibrations. The quality of the double lock nuts is recognized in varius inudstries. The nuts also fulfill an important role in supporting the safety of infrastructure such as highway bridges.
*Eccentric: The substance's center of mass and center of rigidity are separated.

Achieving high quality, short delivery time, and low cost through in-house production

When using the Fuji Double Lock Nut, the convex bottom nut is set on the bolt, after which the concave upper nut is tightened. The tempered part of the concave nut fits tightly with the eccentric part of the convex nut, thus creating a powerful locking effect that prevents looseness.

The manufacturer Fuji Seisakusho Co., Ltd. performs integrated production of various nuts. The company factory has obtained ISO9001 and JIS certification. Achieving short delivery time and low cost through strict quality control and efficient production.

In addition to general stock items, Fuji Seisakusho achieves low cost and short delivery time for special materials and special sizes. The company handles production from a single item to mass production. Moreover, the company has established a cycle to promptly reflect customer requests in products. This flexible and speedy response has led to even greater trust from the market.

Widely used in industrial machinery, bridges, railways, power plants, etc.

In addition to places where there is concern for screws loosening due to frequent vibration, this product is also effective when necessary to reduce the time and cost of maintenance due to labor shortages, etc. The product has a wide range of applications including industrial machinery, roads, bridges, railways, power plants, and seismic isolation devices for skyscrapers.

Another one of the company's strengths is the development of various original products for resolution of on-site issues. One example is the Fuji Quick Lock Nut (patented in 2017), which can be easily installed in any location in about 5 seconds and withstands the same load testing as normal nuts. Through such products, the company contributes to increased efficiency and reduced total costs.

Coverage date October 21,2019


Company overview


A nut manufacturer founded in 1943. The company's head office and factory are located in Higashi-Osaka City, Osaka Prefecture. Develops, manufactures, and sells a wide variety of nut products made of ordinary steel and special alloy steel. Constantly stocks more than 10,000 types of nuts in a wide range of materials, sizes, and pitches. The company can manufacture special products starting from a single item in a short delivery time.

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