A head for brush cutter for cutting grass and herbaceous plants, of the type comprising: - a plurality of cutting elements of the blade type and each having a front cutting portion, defined by an elongated section, and a rear hooking portion, connectable to the head due to a slotted section; - a support body, engageable with a drive shaft of a brush cutter to rotate around an axis of symmetry of the support body, having a central portion, connectable to the drive shaft, and a peripheral portion, having a substantially disc-shaped conformation extending from the central portion radially around it; - a plurality of pins, engageable by the plurality of cutting elements through the insertion of the slotted section of a respective cutting element on a corresponding pin, radially distributed on the peripheral portion; each pin having at least one outer surface having a first side facing the central portion; - a plurality of keys connected to the central portion of the support body; each key being engageable in contact with a respective pin and movable, under the activation by an operator, from a first position, in which the key is in contact with the side of the pin to which the key is facing, to a second position, in which the key is spaced apart from the side generating a passage opening adapted to allow the engagement of the cutting element on the pin due to the insertion of the slotted section on the pin; - a plurality of elastic means, active on the plurality of keys to counteract their movement and distributed so that a respective elastic means is active on each key, said plurality of elastic means being adapted to return the plurality of keys from the second position to the first position once the action induced by the operator has ceased; characterized in that each key, belonging to the plurality of keys, moves from the first position to the second position and vice versa according to a radial trajectory passing through the axis of symmetry of the support body. - a plurality of cutting elements of the blade type and each having a front cutting portion, defined by an elongated section, and a rear hooking portion, connectable to the head due to a slotted section; - a support body, engageable with a drive shaft of a brush cutter to rotate around an axis of symmetry of the support body, having a central portion, connectable to the drive shaft, and a peripheral portion, having a substantially disc-shaped conformation extending from the central portion radially around it; - a plurality of pins, engageable by the plurality of cutting elements through the insertion of the slotted section of a respective cutting element on a corresponding pin, radially distributed on the peripheral portion; each pin having at least one outer surface having a first side facing the central portion; - a plurality of keys connected to the central portion of the support body; each key being engageable in contact with a respective pin and movable, under the activation by an operator, from a first position, in which the key is in contact with the side of the pin to which the key is facing, to a second position, in which the key is spaced apart from the side generating a passage opening adapted to allow the engagement of the cutting element on the pin due to the insertion of the slotted section on the pin; - a plurality of elastic means, active on the plurality of keys to counteract their movement and distributed so that a respective elastic means is active on each key, said plurality of elastic means being adapted to return the plurality of keys from the second position to the first position once the action induced by the operator has ceased;