Each lamination of the lamination stack comprises at least one assembly of coupling elements, said assembly comprising one insertion clamp, one receiving clamp and at least one receiving window, said coupling elements maintaining the same relative positioning from one another, the insertion clamp and the receiving clamp being defined by respective portions of the lamination axially projecting to the same side of the latter, each insertion clamp of a lamination being fitted, by interference, in the interior of a receiving clamp of an adjacent lamination, and each receiving clamp of a lamination being housed in the receiving window of at least one lamination of the stack.