Assembly element including two superposed strip shaped elastic structures and timepiece fitted with the same

An assembly element made in a plate of brittle material such as a silicon, particularly for a timepiece, including an aperture provided for the axial insertion of an arbour, the inner wall of the aperture including elastic structures which are etched into the plate and which each include at least one support surface for gripping the arbour radially in order to secure the assembly element relative to the arbour, wherein each elastic structure includes a first rectilinear elastic strip which extends along a tangential direction relative to the arbour, the support surface being arranged on the inner face of the first elastic strip, wherein each elastic structure is formed by a radial stack of several parallel elastic strips, each elastic strip being separated radially from the adjacent elastic strip by a rectilinear separator hole in two parts, the two parts of the separator hole being separated by a bridge of material which connects the two adjacent elastic strips and which is substantially aligned radially with the support surface, and wherein the last elastic strip of the stack, which is located on the opposite side to the first strip is separated radially from the rest of the plate by a hole in a single part, called the clearance hole, which defines a radial clearance space for the elastic structure.