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HARDLOCK: fastening excellence for the toughest environments

Interview - August 2, 2023

From indispensable industrial machinery to towering bridges, the HARDLOCK Nut has an unbeatable track record in tough operational environments.


When comparing HARDLOCK to regional rivals, can you tell us about what you believe to be your core strengths, or competencies, that set you apart in a field like fasteners, that are usually high volume and very price competitive? In that environment, what sets HARDLOCK apart?

First and foremost, let me explain the mechanism of the bolted joint. There’s a bolt and a nut, and when you tighten the nut on the bolt, there must be a gap in between the threads, without which self-loosening never occurs. Turning the nut on to the bolt until it’s securely fastened is actually like twisting a cloth, so natural forces untwist it by themselves, and the bolt always tries to go back to its natural state, but the nut keeps stopping it by the friction on the threads and the bearing surfaces.

However, with continuous vibration, the nut may no longer be able to hold the bolt, and the bolt may try to go back to its natural state by untwisting itself. Manufacturers globally are trying different methods to prevent this untwisting, such as adding resin between the threads, making the threads distorted just as filling in this gap to create friction.

The unique method of HARDLOCK is inspired by the traditional Japanese construction method of using wedges, for example, in the construction of shrines and temples. Japanese traditional shrine/temple architecture basically doesn’t use nails, but rather assembles parts and sometimes fills the gaps between them with triangle wedges.

We applied this wedge method to fill in the gap between the bolt and the nut threads. The drawing shows the progression of our products, with the rightmost picture showing the final outcome of our anti-loosening nut called “HARDLOCK Nut”. The protrusion of the lower nut is off-centered acting as a wedge.

By Adjusting how much gap we tolerate, the bolt and nut become one piece. The uniqueness of our HARDLOCK Nuts is that they can be removed easily and reused, unlike conventional lock nuts that can only be used once. Our shape also allows us to use any type of material for manufacturing. Since our HARDLOCK mechanism makes the unit one piece by tightening, our products have been so strong that they can replace welding nuts.


I'm curious to know more about how the HARDLOCK alternative can align with sustainable manufacturing. How many times can a HARDLOCK nut be reused, and how else can your technology support more sustainable manufacturing practices?

Our HARDLOCK mechanism is reusable unless the nut or bolt is damaged. In our experiments, we have observed that it can be reused up to 50 times. This makes it a suitable choice for customers who need a self-locking solution that can be easily recycled and reused.

The HARDLOCK brand has a number of unique characteristics. Firstly, it is a one-of-a-kind self-locking nut in the world, accurately utilizing the traditional Japanese wedge technology. This has been verified by third-party analysis and academic papers.

Secondly, our HARDLOCK Nut never loosens up once properly installed, unless there is an initial failure in manufacturing. This is achieved by using two nuts, which allow for pressure to be applied from both sides, eliminating gaps and ensuring stability. You don’t need too much force to tighten it because self-locking power is created by combining the top and bottom nut by itself. That is the uniqueness of our product.

Thirdly, our HARDLOCK Nut can be used as many times as needed until the bolts or nuts are damaged. Fourthly, our product’s versatility allows it to be used with any type of material including resins. This makes it suitable for a wide range of applications, such as in satellites that require 3mm titanium self-locking fasteners.


You have been involved in some renowned civil engineering projects, such as the Tokaido Shinkansen and the Great Seto Bridge, as well as quality-sensitive sectors like aerospace and semiconductor manufacturing tools. Is there a specific type of client that you expect will be a growth market in future, or that your current R&D is focused on?

We anticipate growth in markets such as chemical plants and nuclear power plants where inspections and maintenance are difficult to carry out, as well as in high-temperature environments such as gas turbines, where temperatures of 500 degrees Celsius are reached, and construction of earthquake-resistant buildings in earthquake-prone areas like Japan. We can use nickel alloys to make our nuts, which are heart resistant to 700-800 degrees Celsius. Other applications include high rise buildings or bridges that are difficult to inspect.

Our HARDLOCK Nut has also been used in machinery and mechanisms, stopping which for maintenance could cause a considerable amount of loss in time and cost, such as wind power generators and automotive production lines to achieve a maintenance-free solution. Furthermore, our nuts are predominantly used in applications which require safety at higher levels in extreme conditions and environments, including Shinkansen trains, rail tracks, amusement park rides, construction machinery, and especially mining equipment that is subject to excessive vibrations.

To summarize, our HARDLOCK Nut offers unique advantages in terms of reusability, self-locking capability, versatility with different materials, and stability in various environments. We continue to focus on research and development to provide innovative solutions for our customers in a wide range of industries.

Is there a particular application, whether it be the ISS or the Shinkansen, where you take some pride, or would people be surprised to know that your technology is at the core of what keeps them safe?

We are most proud that HARDLOCK Nuts have been involved in zero accidents in safety-critical applications. Notably, since 1992, over 1.5 million sets have been used annually for Shinkansen. Additionally in the UK, more than half a million sets have been installed on stretcher bars since 2003. This 0% failure rate on stretcher bars application led to full acceptance of HARDLOCK Nuts for use on non-welded railway joints also in the UK.

We are currently focusing on a global trend of infrastructure growth, especially in developing nations, and the maintenance involved requiring high expertise and experience. We are collaborating with JICA (Japan International Cooperation Agency) and other companies to launch our products in these nations and contribute to the safety of infrastructure, as our HARDLOCK Nut solution provides maintenance-free solutions.


Are you currently looking to form international partnerships to increase your scope and introduce your technology to a more global audience?

We are actively seeking partners in the localities where we have evolved. Nevertheless, most parts of our international operations remain dependent on working with Japanese companies that go abroad. When global Japanese companies go abroad, or local companies are using equipment originated or designed in Japan, entities in the locality place orders with us for HARDLOCK Nuts for replacement purpose.

However, finding partners overseas is important to overcome the challenges and increase our expansion. We have started a project with JICA to find partners ourselves in localities and grow the market together. Our mindset is to make contributions towards creating a safe and sustainable society in the locality, and we want to play a role in supporting the growth of infrastructure, especially in developing countries.

Now we are trying to create a safety package, both in terms of hardware and software. We are not only providing the nut, but also an integrated proposal on how to design safe bolted joints and install fasteners without fail.We cannot create this total package all by ourselves, so we want to collaborate with other companies and institutes all around the world to achieve our goals.

During Covid, two years ago, we launched a website that serves as an encyclopedia of tightening fasteners. It is a solution navigation website launched in Japanese, providing all the information on bolted joints including design and analysis, self-loosening mechanism and possible failures describing them from experimental and technical aspects.

Designers and architects are often aware of structural design and strength calculations but may not fully understand how bolted joints work, even in major companies. Our website has been accessed by over 560,000 visitors increased by about 20,000 in a two-year period. We are constantly updating the website. It has an academic perspective, and we also have papers and comments by university professors. We are now working on translating it into English so that it can be promoted globally.

We are making new R&D attempts, working together with startup companies and academia in tripartite collaboration. For example, we are trying to develop a paint that can indicate whether a nut has been correctly fastened or not. We are also trying to receive funds from the government to collaborate and develop high tensile resin material that could replace a usual fastening system.

Once we can develop a high tensile resin that is equivalent to steel, we will be able to reduce the amount of steel and new applications would open up, such as for drones or flying cars, due to its lightweight nature.


Your company is celebrating its 49th anniversary this year, so let's imagine we come back six years from now for your 55th anniversary and have this interview again with you. What would you like to tell us about your dreams for the company and what goals would you like to have accomplished by then?

Our mission and vision are to contribute to people, companies, and the industry by providing unparalleled self-locking nuts, or solutions incorporating them, that ensures safety and assurance for society. My vision is to eliminate any issues caused by bolt loosening and create a world where no one is troubled by them.

To achieve this, we aim to increase partnerships with companies that share our mission and vision, and provide a safe and reliable bolted joint mechanism for global society. We are not only focused on pursuing profits for our company, but also thinking globally about how we can contribute and support society altogether. In five years’ time, we envision that the high tensile resin fastener mechanism will be established and revolutionize the global industry. Within this framework, we aim to continue our global contribution.