Screw-driving tool and corresponding screw

A screwing tool with a longitudinal axis comprising, according to said longitudinal axis:

• a first part, which is configured to receive torque applied by a user or by a tool-holder;
• and
• a second part, which is secured in rotation to said first part on a first part side, the second part being configured to cooperate with a screw, in order to re-transmit the received torque to the screw, said second part having a peripheral envelope with a generally conical form and a base, the base being situated on said first part side, the second part having three longitudinal concavities with regularly distributed conical generatrices, defining three identical radial transmission lobes, each of the three identical radial transmission lobes being defined by, in a cross-section perpendicular to said longitudinal axis,
• two connection portions each being defined by a curve comprising a substantially radial main part, and
• a distal tangential portion which extends substantially according to an arc of a circle, the distal tangential portion being extended on both sides by the two connection portions, each of the connection portions having a point of inflection before re-joining a respective proximal joining region which ensures the joining with an adjacent connection portion of an adjacent radial transmission lobe, the respective proximal joining regions being disposed between the adjacent connection portions of the respective adjacent radial transmission lobes and being the most interior portion of the respective radial transmission lobe in relation to the longitudinal axis, said proximal joining regions having a first cone angle defined in relation to the longitudinal axis which is smaller than a second cone angle of said distal tangential portions defined in relation to the longitudinal axis, the first cone angle being between 1° and 3°, said proximal joining regions being configured to be brought into direct contact with corresponding proximal joining regions of a corresponding screw into which said screwing tool is inserted substantially all along the depth of insertion.