Oswald Dabergotz joined his stepfather's company as a journeyman. From then on the company was called Paul Baumert u. Sohn. In March of the following year, Oswald Dabergotz passed his master's examination as a plumber and fitter before the Hannover Chamber of Trade. Oswald Dabergotz now joined the company as a partner, which was henceforth called "Baumert u. Dabergotz Auto-Kühler u. Karosseriebau, Klempnerei u. Installation". In the same year, Oswald Dabergotz married his wife Maria, who worked in the company until her death in 1993.
Oswald Dabergotz spent the war years at home, as he was considered indispensable. The business was considered a supplier to the municipal transport company, the post office, the fire brigade and the police.
During the war years, daughters Bärbel, Rosemarie and Katharina were born, and the long-awaited son Oswald Junior was born in 1949.