A crop cutting device comprising a crop guiding surface including slots extending in a direction of travel of the crop over the crop guiding surface; knives pivotally mounted below the crop guiding surface, each knife aligned with a respective slot and pivotable about a knife axis extending perpendicular to the slots between a retracted inoperative position in which it is located below the guiding surface and an extended operative position, wherein a cutting edge of each knife projects above said guiding surface; operating units associated with a respective knife and configured to being operated to bring the associated knife from the retracted inoperative position into the extended operative position; a selector mechanism to selectively engage the operating units, the selector mechanism including a rotatable shaft extending to the slots between two side plates and carrying engagement elements configured to engage with the respective operating unit.

A pre-cutter assembly includes at least one knife rotatable about a knife rotation axis between a retracted position and a deployed position, and an associated engagement arm rotatable about an arm rotation axis between a latch position securing the knife in the deployed position, and a release position allowing the knife to move into the retracted position. A magnet may be positioned for engagement with the engagement arm when the engagement arm is disposed in the latch position. The magnet is operable to apply a magnetic force to the engagement arm when engaged with the engagement arm to hold the engagement arm in the latch position thereby securing the knife in the deployed position. A cam shaft having a cam lobe may be rotated to selectively move the engagement arm between the release position and the latch position.

A pre-cutter assembly includes at least one knife rotatable about a knife rotation axis between a retracted position and a deployed position, and an associated engagement arm rotatable about an arm rotation axis between a latch position securing the knife in the deployed position, and a release position allowing the knife to move into the retracted position. A magnet may be positioned for engagement with the engagement arm when the engagement arm is disposed in the latch position. The magnet is operable to apply a magnetic force to the engagement arm when engaged with the engagement arm to hold the engagement arm in the latch position thereby securing the knife in the deployed position. A cam shaft having a cam lobe may be rotated to selectively move the engagement arm between the release position and the latch position.