Abstract: In a tool for tightening clamps, of the kind comprising a flexible strip and an apertured head, having a passage in which the end of the flexible strip can be engaged after the strip has been passed around a bunch of articles to be clamped together and through the apertured head, the tool being used to cut-off that portion of the flexible strip of the clamp which projects beyond the apertured head following tightening to a greater or lesser degree of the clamp around the articles, the improvement comprising a displacement member, a trigger and coupling means including a swinging link provided between the displacement member and the trigger and including a sudden release mechanism comprising a cam having a cam surface with two separate stable zones separated from one another by an unstable zone and a cam-follower maintained in contact with the cam surface of the cam, the cam and the cam-follower being relatively movable to swing said cutting lever from a rest position into a working position, one of the cam an