A portable drilling and/or boring machine, for workpieces, in particular workpieces that make up aeroplane structures, such as airframes, wings, cabin, etc., the machine including a jig busing for guiding a machining tool, an expansible clip for blocking the jig bushing in an opening of a screen positioned on and secured to the workpiece, the screen constituting a drilling jig, and means for moving the expansible clip in order to clamp and unclamp the jig bushing and secure the machine relative to the screen, the means for moving the expansible clip relative to the jig bushing including an electric motor, the torque and position of which are controlled.