Abstract: In a device for coupling a tooth onto an adaptor nose with a key, the tooth includes a skirt shrouding the adapter nose beyond the key passage zone and having a configuration connected to a return wall, comprising a bordering ridge. The wall is provided in the width of the skirt and corresponds to the passage and positioning of the key. Proximate the ends of the wall, and in the thickness of the skirt, are provided passage openings for the key devoid of abutting function in operation and ensuring a guiding and stopping function only when the key is inserted or removed. The key comprises two components transversely mobile relative to each other.