A surgical tool-piece (110, Fig 5) and a coupling mechanism (Fig 7) for attaching the tool piece to a driving mechanism comprises at least three coupling elements allowing the tool piece to engage with a driving mechanism and/or the coupling mechanism, such that it is secured longitudinally and rotationally. The coupling mechanism comprises a sheath 210 which forms an internal longitudinal cavity for receiving a coupling section 120 of the tool piece and the three coupling elements 220 are disposed on the mechanism opposing each other and configured to move radially outwardly to allow at least a part of the coupling section of the tool piece to pass them and are urged radially inward toward the central longitudinal axis in order to secure the tool-piece in position (for example by an O-ring 250). In the case of the tool piece (110, Fig 5) the coupling elements are located on a shaft of the piece, forming a coupling portion (120, Fig 5) comprising at least three indentations (130, Fig 3C) radially located around the circumference of the said portion.
