Manufacturing process of a flywheel comprising the following steps: a) cutting and drilling a sheet metal to obtain a first semi-finished part composed of a disk having a central hole and a plurality of first holes that are equally spaced along a circumference, b) preforming the disk of the first semi-finished part to obtain a second semi-finished part with a central flat portion around the central hole, an intermediate flat portion that is raised with respect to the central portion, a peripheral portion that is lowered with respect to the intermediate portion, two projections disposed in diametrically opposite position in said peripheral portion, a peripheral truncated-conical edge that protrudes from the peripheral portion, wherein said first holes are in the intermediate portion, c) preforming the central portion of the second semi-finished part to obtain a third semi-finished part with a cylindrical shank in central portion around the central hole, d) forming the peripheral edge of the disk of the third semi-finished part to obtain a fourth semi-finished part with peripheral cylindrical edge, e) drilling the disk of the fourth semi-finished part to obtain a fifth semi-finished part with a plurality of second holes that are equally spaced along a circumference in said central portion of the disk, f) extrusion of two pins in the central portion of the disk to obtain a sixth semi-finished product with the coined holes (10, 15, 14) and two pins that protrude in the central portion of the disk, and g) extruding said central shank of the sixth semi-finished part to obtain the finished flywheel comprising a central hub obtained from extruding said central shank of the disk, characterized in that said disk of the first semi-finished part comprises two opposite linear edges, the two projections of the second semi-finished part are disposed in correspondence of said opposite linear edges of the disk of the first semi-finished part, and said extrusion step (f) also provides for coining said central hole, first holes and second holes of said fifth semi-finished part. a) cutting and drilling a sheet metal to obtain a first semi-finished part composed of a disk having a central hole and a plurality of first holes that are equally spaced along a circumference, b) preforming the disk of the first semi-finished part to obtain a second semi-finished part with a central flat portion around the central hole, an intermediate flat portion that is raised with respect to the central portion, a peripheral portion that is lowered with respect to the intermediate portion, two projections disposed in diametrically opposite position in said peripheral portion, a peripheral truncated-conical edge that protrudes from the peripheral portion, wherein said first holes are in the intermediate portion, c) preforming the central portion of the second semi-finished part to obtain a third semi-finished part with a cylindrical shank in central portion around the central hole, d) forming the peripheral edge of the disk of the third semi-finished part to obtain a fourth semi-finished part with peripheral cylindrical edge, e) drilling the disk of the fourth semi-finished part to obtain a fifth semi-finished part with a plurality of second holes that are equally spaced along a circumference in said central portion of the disk, f) extrusion of two pins in the central portion of the disk to obtain a sixth semi-finished product with the coined holes (10, 15, 14) and two pins that protrude in the central portion of the disk, and g) extruding said central shank of the sixth semi-finished part to obtain the finished flywheel comprising a central hub obtained from extruding said central shank of the disk,