Method for achieving final air gap and parallelism of a control valve of a fuel injector, said control valve having a body extending about a main axis from an transverse top face to an opposed lower face and being provided with an axial hydraulic bore opening in a recess, said recess defining a chamber opening in said top face, the control valve being further provided with a spool comprising a disc magnetic armature having an axial central drilling opening at each ends in a planar transverse upper face and an opposed lower face and, a stem fixed in said central drilling, said spool being arranged in the body in a rest position wherein, the stem is axially guided in the hydraulic bore and, the armature lies in the chamber, the armature upper face being slightly recessed from the body top face, characterised in that the method comprising the following steps: a) measuring the actual position from the armature upper face and the body top face and, determining the actual parallelism error between said faces (18, 30), the actual parallelism error being the angular tilt of the planar transverse upper face relative to the top face, wherein the measuring comprises a1) determining the tilt axis and the line of greatest slope of said armature upper face, said tilt axis and line being perpendicular to each other, the tilt axis being the transverse axis about which said upper face is angled; a2) calculating a tilt height between the ends of the line of greatest slope, said tilt height being the distance measured along the main axis from the highest point of the line to the lowest point of the line, the highest point being closer to the top face and the lowest point being further recessed in the chamber; and a3) dividing said tilt height in individual ablating pass depth; the method further comprising b) ablating the armature to correct the tilt height and the parallelism error by generating an ablated upper face parallel to the body top face, the distance from the ablated upper face to the body top face being a final air gap. said control valve having a body extending about a main axis from an transverse top face to an opposed lower face and being provided with an axial hydraulic bore opening in a recess, said recess defining a chamber opening in said top face, the control valve being further provided with a spool comprising a disc magnetic armature having an axial central drilling opening at each ends in a planar transverse upper face and an opposed lower face and, a stem fixed in said central drilling, said spool being arranged in the body in a rest position wherein, the stem is axially guided in the hydraulic bore and, the armature lies in the chamber, the armature upper face being slightly recessed from the body top face, characterised in that the method comprising the following steps: a) measuring the actual position from the armature upper face and the body top face and, determining the actual parallelism error between said faces (18, 30), the actual parallelism error being the angular tilt of the planar transverse upper face relative to the top face, wherein the measuring comprises a1) determining the tilt axis and the line of greatest slope of said armature upper face, said tilt axis and line being perpendicular to each other, the tilt axis being the transverse axis about which said upper face is angled; a2) calculating a tilt height between the ends of the line of greatest slope, said tilt height being the distance measured along the main axis from the highest point of the line to the lowest point of the line, the highest point being closer to the top face and the lowest point being further recessed in the chamber; and a3) dividing said tilt height in individual ablating pass depth; a) measuring the actual position from the armature upper face and the body top face and, determining the actual parallelism error between said faces (18, 30), the actual parallelism error being the angular tilt of the planar transverse upper face relative to the top face, wherein the measuring comprises a1) determining the tilt axis and the line of greatest slope of said armature upper face, said tilt axis and line being perpendicular to each other, the tilt axis being the transverse axis about which said upper face is angled; a2) calculating a tilt height between the ends of the line of greatest slope, said tilt height being the distance measured along the main axis from the highest point of the line to the lowest point of the line, the highest point being closer to the top face and the lowest point being further recessed in the chamber; and a3) dividing said tilt height in individual ablating pass depth; the method further comprising b) ablating the armature to correct the tilt height and the parallelism error by generating an ablated upper face parallel to the body top face, the distance from the ablated upper face to the body top face being a final air gap.