For hundreds of years, water mills have supported the local economies of Piedmont by contributing to the production of flour, textile fibres, timber, and metal agricultural tools. Since the beginning of the last century, and in particular after the 1950s, many artefacts have been abandoned. Nonetheless, hundreds of mills are still present in southern Piedmont, both in the plains and in the mountains, sometimes in an excellent state of conservation. This work presents a hammer forge, the La Pianca mill in Busca, Cuneo, Italy, as a significant, detailed case study. The socio-economic context in which exists is analysed, its history is reconstructed, and the functioning of the machinery, including the water wheels, the motion transmission systems, and the various utilities consisting of tilt hammers, grinding wheels, and drills, is analysed in detail. Beyond the historical interest, concerning both the territory and the architecture, as well as the machines and mechanisms, this work aims to make a contribution to the prefiguration of effective scenarios for the reconversion of similar productive artefacts.