Protection of a timepiece component made of micromachinable material

A timepiece sub-assembly comprising:

• a timepiece component made of micromachinable material comprising at least one attachment area;
• and
• a shell element arranged to surround said at least one attachment area, said at least one 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 at least one attachment area inside a housing contained in said shell element, and said shell element comprising at least one complementary contact surface configured to, in said contracted shape of said shell element, exert a clamping force on said at least one peripheral contact surface and firmly immobilize said at least one 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 said at least one expanded shape, the first and second element comprising a first and second complementary contact surface, respectively, of said at least one complementary contact surface, and
• wherein said shell element comprises clamping means configured to hold at least said first element and second element clamped to each other in said contracted shape of said shell element.