The call came from his brother-in-law, Louis Peters, who had just taken over the bankrupt plant of Hüsing & Company in Warstein. The works made spades, shovels, hay forks, manure forks - the unromantic edge of farm equipment, forged from steel and iron. Peters wanted Emil to come and run the commercial side. By 1895 Emil had recruited his younger brother Hugo, and the two of them, though Peters' name remained on the door, had become the actual engine of the business. About ninety people worked there. They were already, in their early thirties, influential local industrialists in a town of a few thousand.

Over the next two decades the brothers reshaped the company. Drop forging replaced hand work. New customers arrived: bicycle manufacturers at the turn of the century, then the early automobile industry, then the railway industry. In 1916 - in the middle of a world war - they installed a new hammer with an 85-ton anvil, the heaviest in any German production plant at the time. Every bridge between Soest and Warstein had to be reinforced before the anvil could be transported. That single piece of metal turned the Siepmann works from a regional drop-forge into something approaching a national one. The number of employees grew, the catalogue grew, and the Siepmann name began to mean something across German industry.

Emil married Marie Magdalene Schuette in 1896, and they had five children, of whom four reached adulthood. One son, Hans, was deemed the heir to the family business; he died of unknown cause in 1919, aged twenty-two. The grief seems to have pushed the Siepmann brothers further into philanthropy. In 1921 they donated 250,000 marks - roughly a million dollars today - for the construction of a children's home on the North Sea island of Norderney, a place where city children from industrial Westphalia could come to breathe salt air. Emil also served on the district council of Arnsberg from 1904 to 1915, campaigning for railway connections and a local power station, and was on the board of the Warstein savings bank from 1909 to 1929.

Emil and Hugo Siepmann lived next door to each other on Hauptstrasse in Warstein - Hugo at number 145, Emil at number 143, two houses on a split parcel of land where their families' children grew up together. They worked together for sixty years. Emil died on 2 November 1950, aged eighty-seven, just four weeks after his younger brother. When both patrons of the largest employer in the region were carried to their graves within a month of each other, a ceremonial procession formed in the streets of Warstein, hundreds of attendees marching behind the coffins of the two men who had, together, made the town what it was.