Each of wire driving means (24) for driving printing wires (22) of a printing head (10) is radially arranged along a predetermined reference plane (P) and provided with an air gap (36) and a magnetic frame (26), said air gap extending in a first direction (X-X) and housing an armature (54) for driving the printing wire (22) and said magnetic frame (26) forming a magnetic circuit provided with a permanent magnet (30b). The magnetic frame (26) has at least one connecting portion slidable both in the first direction (X-X) and in a second direction perpendicular to the first direction (X-X) by means of its sliding planes (30c, 32c) parallel to a plane including both the first direction (X-X) and the second direction perpendicular to the reference plane (P), and the connecting portion is fixed by means of screws (46) arranged substantially perpendicular to sliding planes (30c, 32c), said screws (46) being provided with a clearance around them, respectively.