The device for fast assembly of a tool on its support comprises a bolt attached to said support and disposed within a bore with a through hole and a mandrel, which is attached to the tool as such and disposed within said through hole and interacting with said bolt. At the junction between the tool and its support, the device comprises centering and locking means which consist of a set of the tenon and mortise type, which set extends perpendicularly to the mandrel and thus forms a T-shaped structure of the assembly, which confers high rigidity to the tool. Said assembly device is in particular suitable for tools such as actuators or pliers, i.e. tools which are utilized in machines for packaging flasks, bottles or the like.