Protection of a timepiece component made of micromachinable material

A timepiece sub-assembly comprising, on the one hand, a timepiece component made of micromachinable material comprising at least one attachment area, and on the other hand, a shell element arranged to surround said attachment area, said attachment area comprising at least one peripheral contact surface, and said shell element being deformable with a geometry varying between a contracted shape and at least one expanded shape, and arranged to hold said attachment area inside a housing contained in said shell element, and said shell element comprising at least one complementary contact surface arranged, in said contracted shape of said shell element, to exert a clamping force on said at least one peripheral contact surface and to firmly immobilise said attachment area inside said shell element in all directions, wherein said shell element comprises at least a first element and a second element, movable with respect to each other in a said expanded shape, each comprising a said complementary contact surface, and wherein said shell element comprises clamping means for holding said at least a first element and second element clamped to each other in said contracted shape of said shell element.