1000 x SD Screw 55x5.5mm Countersunk Head - #5 Point with Wings

These screws, with the #5 self drilling point with extra long cutting flutes, are specially designed to drill through steel up to 12mm thick, cut their own mating threads and fasten securely in one simple operation. The clever wings on these countersunk head screws, drills a clearance hole in timber. This prevents the timber from rising up as the screw penetrates the metal, and negates the need for pre-drilling. As the screw point drills through the metal base material, the wings break off, the thread is formed and the head clamps down to secure the timber.