Selective coupling device for a collet chuck

A handpiece intended for dental or surgical applications, the handpiece comprising:

• a transmission rotor, and
• a drilling tool,
• wherein the transmission rotor comprises:
• an input element comprising a turbine or a drive pinion,
• an output element comprising a drive shaft rotatable about an axis of rotation, said drive shaft being adapted for actuating rotation of said drilling tool around said rotation axis, and
• a clamping device,
• said clamping device comprising a clamp disposed inside said drive shaft for axially securing said drilling tool with respect to said axis of rotation, said clamp being configured to cooperate with a plunger for release of said drilling tool, as well as a radial guide bush of said drilling tool, said plunger configured to rotate integrally with said drive shaft,
• said clamping device further comprising a coupler between said clamp and said guide bush, said coupler being configured to exert an angular holding torque between said clamp and said guide bush, a value of the angular holding torque being inferior to that corresponding to a slip threshold between said clamp and said drilling tool.