A device for the assembly of at least two standard elements of a precision mechanical structure by a linking element, where the first standard element includes a reference surface, while the second standard element includes a bearing surface which has to be positioned with precision in an orthonormal coordinate system associated with the aforementioned reference surface, given that the connection between the linking element and at least one of the standard elements includes two contact faces provided on the linking element and the standard element. A clamp composed of two half collars, and presenting shapes which interlock with the corresponding shapes of the linking element and of the standard element in such a way that the clamping of the two half collars causes the application and the centering of the two aforementioned contact faces against each other.