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Latest update: 03/04/2020 15:49:35

Kohwa Co., Ltd.

Friendly to wood and strong

We manufacture hardware for civil engineering and construction. This includes Japan's first screw-stopped hold-down hardware, steel struts using double-threaded screws, square recess screws, and subsidiary materials (such as stairs and balconies). 

Main image

Sales Pitch

About our company's products 
[Square recess screws]
In 1990 we began to manufacture screws having a square recess in their heads rather than a cross-shaped recess. We were ahead of other manufacturers in this, so we can take pride in our many years of experience. The features of our square recess screws are as follows.

- Excellent torque transmission
- They only need to be pushed lightly once they bite into lumber. That's all they need.
- Work efficiency improves by 20% to 30% compared with a case where Phillips screws are used. 
- Bits are long-lasting.

[Overturning preventing function]
The grooves made on a workpiece and the serrations made on the back side of the coach screw work together to break the bit if excessive torque is applied. This prevents lumber from being broken due to excessive turning and the screw from being broken due to excessive torque. However, if the material of the workpiece is thin, this function may not be exhibited.

[Product performance evaluation]
The following tests have been performed by accredited testing agencies to assure product performance. 
(1) Performance certification test  (Japan Housing and Wood Technology Center)
(2) Quality performance certification test (Japan Testing Center for Construction Materials)
(3) Construction technique certification test (The Building Center of Japan) 
Surface treatment technology: BIK coating treatment corrosion-prevention technology for galvanized hardware for construction using a non-chromium rust inhibitor
Electrogalvanizing and painting using hexavalent chromium are widely performed as surface treatment of screws, bolts, and other hardware for construction.

However, many companies in the construction industry now need surface treatment that does not use hexavalent chromium from the viewpoint of environmental conservation. This is why we developed BIK coating surface treatment technology.

A BIK coat is formed by dipping an electrogalvanized steel member in BIK coating solution and drying it. It is just 1 to 2 µ in thickness but exhibits excellent rust prevention performance equal to or higher than a chromate film.

1. High rust prevention performance 
BIK coating exhibits high rust prevention performance in salt spray tests and complex corrosion tests (cycle tests) when applied to a galvanized surface.
2. Endures repeated drying and wetting.
Coating films are usually severely damaged in an environment where drying and wetting are repeated. However, BIK coating repairs its damaged portion with its self-recovery capability, maintaining its high rust prevention performance.
3. Screwing resistance
Exerts high adhesiveness, and thus does not come off easily when a wood screw or self-tapping screw bites in.
4. Water and moisture resistance
Does not readily rust or separate even in water or in highly humid environments.
5. Friction coefficient
Exhibits a friction coefficient of approximately 0.3 without much variation, which secures high workability of wood screws and self-tapping screws.
6. Perfectly chrome-free, and thus friendly to environment 
No chrome is used, to contribute to environmental conservation.

This company is recommended by the following support organizations.

Kanto Head Office, SMRJ

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