OHKI Brass & Copper Co., Ltd.

OHKI Brass & Copper Co., Ltd. (大木伸銅工業株式会社) is a Japanese non-ferrous metals manufacturer specialising in wrought copper and copper-alloy products. The company traces its origins to November 1924 (Taishō 13), when Iwao Ohki began manufacturing brass rods as a sole proprietorship in Kitamachi, Nerima Ward, Tokyo. It was reorganised as a limited partnership, Ohki Shindō-sho, in 1933, and incorporated as Ohki Shindō Kogyo Co., Ltd. in 1942, absorbing the earlier partnership. Its head office and main sales office remain in Tokumaru, Itabashi Ward, Tokyo, with a major production plant in Niiza, Saitama Prefecture, plus branches in Suwa (Nagano) and Utsunomiya (Tochigi). The company's core product lines are brass rods (黄銅棒), phosphor bronze sheet and strip (りん青銅), and hot die forgings (鍛造品) made from its own copper rods, forging brass rods and high-strength brass rods. Its brass rods are produced with integrated equipment covering everything from raw-material melting to finished product, including horizontal continuous casting and indirect extrusion, which the company highlights as improving productivity, reducing internal defects and delivering uniform mechanical and physical properties with tight dimensional accuracy. Its phosphor bronze range includes C5111, C5191, C5212 and C5210 grades in plate and strip form, used for springs, switches, connectors, relays, lead frames, diaphragms, bellows, fuse clips, sliding contacts, washers, bearings and bushes in electronic and electrical equipment. OHKI positions itself as a customer-responsive specialist with "overwhelming inventory" for immediate delivery, nationwide shipping coverage, and strong technical and proposal capabilities. It is an owner-managed, unlisted company with stated capital of 100 million yen and 216 employees (as of 1 January 2022). Its group includes the affiliate OKB Co., Ltd. (オーケービー株式会社), which operates a plant in Minakami, Gunma Prefecture. Raw materials are purchased from suppliers including Mitsubishi Materials, Toho Zinc and Itochu Metals, and its major customers include LIXIL, Sanden, Panasonic, Nitto Kohki, Hitachi Metals and Pilot Corporation. The company continues to invest in equipment and human resources, and in January 2022 formulated a three-year action plan for next-generation development and women's advancement. It maintains a corporate philosophy of "reform and daily renewal" (改革日新) and "co-existence and co-prosperity" (共存共栄) with affiliated and partner companies, and aims to be a copper-rolling maker boasting Japan's finest quality.

OHKI Brass & Copper Co., Ltd. was founded in November 1924 (Taishō 13) when Iwao Ohki began manufacturing brass rods as an individual business in Kitamachi, Nerima Ward, Tokyo. In October 1933 (Shōwa 8), the business was incorporated as the limited partnership Ohki Shindō-sho (合資会社大木伸銅所), and a new Tokumaru plant was established in Itabashi Ward, where production expanded from brass rods to include brass sheet. In October 1942 (Shōwa 17), the company was reorganised as Ohki Shindō Kogyo Co., Ltd. (大木伸銅株式会社), absorbing the limited partnership and increasing capital to 2 million yen. Post-war expansion followed: in October 1953 the company began manufacturing brass tubes, and in October 1954 it added brass strip. In May 1961 capital was increased to 100 million yen. In March 1962 the Niiza Plant was established in Niiza City, Saitama Prefecture, where brass tube production began. The company continued to broaden its product range and production capacity through the following decades, developing capabilities in phosphor bronze sheet and strip and in hot die forgings. By the 2020s the company operated from its head office and main sales office in Tokumaru, Itabashi Ward, Tokyo, with the Niiza Plant in Saitama, and branches in Suwa (Nagano Prefecture) and Utsunomiya (Tochigi Prefecture). Its affiliate OKB Co., Ltd. operates the Tsukiyono Plant in Minakami, Gunma Prefecture. As of 1 January 2022 the company reported 216 employees and stated capital of 100 million yen. It remains an owner-managed, unlisted company, with Soji Ohki serving as Representative Director and President. In January 2022 the company formulated a three-year action plan for next-generation development and women's advancement. It has also issued price revision notices for brass rod and other copper alloy products, reflecting changing raw-material and market conditions. The company describes its corporate philosophy as "reform and daily renewal" (改革日新) and "co-existence and co-prosperity" (共存共栄), and states its ambition to be a copper-rolling maker boasting Japan's finest quality.

• Iwao Ohki begins manufacturing brass rods as an individual business in Kitamachi, Nerima Ward, Tokyo.

• Limited partnership Ohki Shindō-sho established; Tokumaru plant in Itabashi Ward newly built and brass sheet production begins.

• Ohki Shindō Kogyo Co., Ltd. established, absorbing the limited partnership; capital becomes 2 million yen.

• Brass tube manufacturing begins.

• Brass strip manufacturing begins.

• Capital increased to 100 million yen.

• Niiza Plant established in Niiza City, Saitama Prefecture; brass tube production begins there.

• Formulated a three-year action plan for next-generation development and women's advancement.

• Announced price revision for brass rod and other copper alloy products.

• Launched a new recruitment website.

Specialist copper-alloy maker emphasising overwhelming inventory for immediate delivery, nationwide shipping, integrated production technology and customer-responsive proposals; owner-managed and quality-focused.

• Brass rods

  Produced with integrated equipment from raw-material melting to finished product, including horizontal continuous casting and indirect extrusion for improved productivity, fewer internal defects, uniform mechanical and physical properties and high dimensional accuracy.

• Phosphor bronze sheet and strip

  Copper alloy with tin and a small amount of phosphorus; grades C5111, C5191, C5212 and C5210 in plate (0.15–30 mm thickness) and strip (0.15–1.2 mm thickness) forms, used for springs, switches, connectors, relays, lead frames, diaphragms, bellows, fuse clips, sliding contacts, washers, bearings and bushes.

• Hot die forgings

  Forged products made from the company's own copper rods, forging brass rods and high-strength brass rods, produced under fine-grained quality control.

1. 1創立100年を超える│大木伸銅工業株式会社ohkishindo.co.jp
2. 2会社概要・沿革│大木伸銅工業株式会社ohkishindo.co.jp
3. 3黄銅棒│会社案内│大木伸銅工業株式会社ohkishindo.co.jp
4. 4りん青銅│会社案内│大木伸銅工業株式会社ohkishindo.co.jp
5. 5OHKI Brass & Copper Co., Ltd. (Japan) - Wikidatawikidata.org