A tool for manufacturing a casting core, for a turbomachine blade with a leading edge and a trailing edge, the core includes a thick part on the leading edge side and a thin part on the trailing edge side is disclosed. The tool includes first and second dies of the core that are moveable in a direction with respect to each other between a molding position and a demolding position, sub-components that are moveable relative to the dies, and mechanical ejectors that are provided on the first and second dies. The parts of the dies corresponding to the thin part of the core do not include a movable sub-component. The thin part of the core is demolded along the main direction of opening of the first and second dies.