Columbian Economy Drop Forged C-Clamp 0 - 8” Opening Capacity Drop forged, regular-duty with extra deep throat. Improved frame design allows for a higher proof test, greater throat depth, and lower overall weight. Acme rolled spindle threads provide maximum strength and clamping force. Exceptional value and performance. V grooved anvil allows secure holding of all materials including rounds, squares and flats. OVERVIEW. Columbian Economy C-clamps feature drop forged frames and an oscillating head that provides a tighter hold on angular work pieces. 20305