Former Sumitomo Metal Industries Propeller Factory

The Sumitomo Metal Industries Propeller Manufacturing Plant (住友金属工業プロペラ製造所) was established in May 1933 at Sakurajima, within the grounds of Sumitomo's copper rolling works in Konohana-ku, Osaka. The initiative came after Rear Admiral Isoroku Yamamoto, then head of the Technical Division of the Naval Aviation Bureau, personally visited Sumitomo executive Shunnosuke Furuta in November 1932 to request that Sumitomo enter the metal propeller business. Production began with Hamilton Standard-type propellers manufactured under license from Nakajima Aircraft.

By 1936, annual production had reached 1,800 units. On November 10, 1937, the propeller section was separated from the copper works to become an independent Propeller Manufacturing Plant. Following the outbreak of the Second Sino-Japanese War that year, military demand surged dramatically, and the workforce grew 23-fold to 7,000 within four years. In 1938, a second factory was built in Kanzaki, Amagasaki (Hyogo Prefecture), which began operations on April 11, 1941.

Sumitomo acquired a license for Hamilton Standard constant-speed counterweight propellers and VDM products in the late 1930s. These constant-speed propellers were adopted for the Mitsubishi A6M Zero fighter, replacing the earlier variable-pitch design. Under general manager Osamu Sugimoto, an MIT-educated aeronautical engineer, the Propeller Division grew to operate four manufacturing plants. By July 1944, monthly production reached 5,247 propellers. Over the course of the war, Sumitomo produced approximately 89,885 propellers — 66% of all Japanese military aircraft propellers — including nearly all propellers for the Imperial Japanese Navy and 40% for the Army.

In early 1945, as Allied bombing intensified, emergency dispersal of factory equipment began to locations including Toyonaka, Ikeda, Sanda, and Kainan. On June 15, 1945, U.S. B-29 bombers dropped incendiary bombs on the factory, destroying most buildings and halting operations entirely. By that time, the workforce had peaked at approximately 12,600, including conscripted laborers and student mobilization corps members.

After the war, Sumitomo's propeller business eventually resumed and in 1961 was transferred to the newly established Sumitomo Precision Products (住友精密工業), which continues today as an aerospace components manufacturer. The original Sakurajima factory site in Konohana-ku has been redeveloped as part of Osaka's waterfront industrial transformation.