A portable tool configured to ensure the expansion of a peg (Ch) of a screw (Vs) and peg set wherein: - the screw (Vs) has a screw head (Tv), with a diameter larger than a tapped portion of the screw, - the peg (Ch), having a nut (Ec) at a distal end inside which the screw is screwed, and a shoulder (Ep) at a proximal end, intended to bear on a first face of a wall inside which the peg is inserted, as well as a plurality of branches (Bv) each connecting the nut (Ec) to the shoulder (Ep), and wherein the tool comprises an effector comprising: - a bit having at its distal end a first support provided with a first indentation, having a face intended to come into contact with the shoulder (Ep) of the peg, as well as a slide extending on the side opposite to said face, - a slider, mounted movable in translation along the slide, bearing a second support provided with a second indentation configured to bear against the screw head (Tv), - a drive mechanism configured to move the slider from an initial first position, for which the second support is juxtaposed to the first support enabling the insertion of the screw (Vs) throughout the indentations consisting of the first indentation and the second indentation with contact of the first support against the shoulder (Ep) of the expansion peg (Ch) inside which the screw (Vs) is screwed and whose tapped portion crosses the first indentation and the juxtaposed second indentation, the screw head (Tv) then positioned opposite the second support and up to a second position (P2x; P2y) for which the second support then in contact against the screw head is brought away from the first support in contact with the shoulder (Ep) by sliding of the slider along the slide causing the detachment of the screw head (Tv) with respect to the shoulder (Ep) of the peg, and thus the expansion of the peg (Ch) by deformation of the branches (Bv) by approach of the nut (Ec) and of the shoulder (Ep), the drive mechanism comprising an electric motor comprising a rotor and a stator, as well as a transmission ensuring movement of the slider along the slide during rotation of the rotor, as well as a monitoring module comprising a control member, said monitoring module being configured, when the operator presses on said control member, to actuate the motor in order to drive the slider from the first position towards the second position (P2x, P2y), wherein the control member is an electric button preferably with a normally-open switch, pressing on said control member ensuring the actuation of the electric motor, and releasing the control member ensuring the stoppage of the motor, characterised in that the monitoring member comprises a motor board ensuring the automatic stoppage of the slider in the second position (P2x, P2y) when the slider reaches a determined stroke between said first position and said second position (P2x, P2y) of the slider as well as a user interface configured to ensure setting of the value (x, y) of the determined stroke. - the screw (Vs) has a screw head (Tv), with a diameter larger than a tapped portion of the screw, - the peg (Ch), having a nut (Ec) at a distal end inside which the screw is screwed, and a shoulder (Ep) at a proximal end, intended to bear on a first face of a wall inside which the peg is inserted, as well as a plurality of branches (Bv) each connecting the nut (Ec) to the shoulder (Ep), and wherein the tool comprises an effector comprising: - a bit having at its distal end a first support provided with a first indentation, having a face intended to come into contact with the shoulder (Ep) of the peg, as well as a slide extending on the side opposite to said face, - a slider, mounted movable in translation along the slide, bearing a second support provided with a second indentation configured to bear against the screw head (Tv), - a drive mechanism configured to move the slider from an initial first position, for which the second support is juxtaposed to the first support enabling the insertion of the screw (Vs) throughout the indentations consisting of the first indentation and the second indentation with contact of the first support against the shoulder (Ep) of the expansion peg (Ch) inside which the screw (Vs) is screwed and whose tapped portion crosses the first indentation and the juxtaposed second indentation, the screw head (Tv) then positioned opposite the second support and up to a second position (P2x; P2y) for which the second support then in contact against the screw head is brought away from the first support in contact with the shoulder (Ep) by sliding of the slider along the slide causing the detachment of the screw head (Tv) with respect to the shoulder (Ep) of the peg, and thus the expansion of the peg (Ch) by deformation of the branches (Bv) by approach of the nut (Ec) and of the shoulder (Ep), the drive mechanism comprising an electric motor comprising a rotor and a stator, as well as a transmission ensuring movement of the slider along the slide during rotation of the rotor, as well as a monitoring module comprising a control member, said monitoring module being configured, when the operator presses on said control member, to actuate the motor in order to drive the slider from the first position towards the second position (P2x, P2y),