Founded by Alfred Scholl and Heinrich Bonnat in 1905 under the name "Siegthaler Iron- and Sheet Goods GmbH", the company primarily produced sheet metal products for the agricultural and mining industries. In 1920, Fritz Hench became Managing Director at Siegthaler and the company started to manufacture welded sheet metal constructions and tanks.
In 1935, the company moved to its headquarters in Siegen where it is still today. Shortly before the start of the war the first butt welding machine was put into operation to produce bent and welded rings. In the reconstruction phase after the war, Fritz Hench became the sole shareholder of Siegthaler and restarted the tank and apparatus production as well as the manufacture of compensators, rings and flanges.
In 1973, his children, Werner, Christel and Ulrich Hench took over the company shares and Ulrich was appointed Managing Director of the firm. Two years later, the company was reorganized, the production being concentrated on rings and flanges.

Shortly before the arrival of the new millennium, Mr. Hench passed the company into the hands of  two brothers: Klaus-Dieter and Dietmar A. Wolf, who manage the company to this day. A new chapter in the history of the company was opened by the expansion in production capacity, when a new hall was built for large-scale machinery and the company was completely modernized.
Since 2001, Siegthaler has been able to machine flanges with a maximum diameter of 6,000mm, a dimension which was increased further in 2008 to a maximum of 8,000mm and a unit weight of 50 tons.