Cutter bar (10) of the type applicable to motor mowers or mowers comprising: - a supporting bar (11) - a lower blade or comb (12) sliding along the major axis with respect to the supporting bar (11) comprising a plurality of lower small blades or teeth (13) - an upper blade (14) sliding along the major axis with respect to the supporting bar (11) arranged superimposed on the lower blade or comb and comprising a plurality of upper small blades (15) - a control group (16) configured for imparting an opposite reciprocating motion to the blades (12, 14) - bladeholder devices (17) acting on the upper surface of the upper blade (14) wherein the lower small blades or teeth (13) have a thickness or mass greater than the upper small blades (15) and wherein the upper blade (14) comprises an upper supporting strip (20), to which the upper small blades (15) are constrained through rivets (21), the lower cylinder head (22) of the rivets (21) being housed in lowered seats (23) obtained on the upper face of the lower small blades or teeth (13).
