The DF-1480 bit is our 8.0 mm or approximately 5/16th of an inch High Speed Steel Cobalt (HSCO) spot-weld bit. The twist is the same size as the shank which is also 8.0mm and has a flat spot on it to be tightened into our DF-15DX Series Spot Weld Drills. We also offer this bit with a Titanium heat resistant coating DF-1680T. Our drill bits a specifically designed for the abuse of spot weld drilling. Flat ground for strength, centering nib to prevent walking. Our German made spot weld bits are available in 3 sizes, 6.5 (DF-1465), 8.0 (DF-1480) and 10.0 mm (DF-1610). These Cobalt high-speed steel mix bits are 45mm long.