A cutting head for a string trimmer is provided which accommodates any string gauge thickness and may be easily and quickly re-threaded upon failure of a string previously disposed therein. Clamping members are provided to clamp the strings within the cutter head, with the clamping force being provided by springs and centrifugally generated moments. The clamping members are capable of generating two degrees of clamping force. The lesser degree of clamping force can be overcome by a string forcibly inserted into the cutting head.