Proprietary spiral blade reduces chip welding. Improved blade life.Nice Mighty with a large diameter size and hexagonal shaft(6.35mm)specifications.The shank part uses commercial screwdriver bit, so if the shaft is broken, the issue can be resolved by replacing the bit in a single operation.Work material: Iron/copper plate(up to 2mm), aluminum plate/wood/resin(up to 3mm), stainless steel plate(up to 1mm).Step Width (mm):2.5(3)Number of Stages (stage):11Shank Diameter (mm):6.35Drilling Dimension (?3mm):(6), 13, 15, 16, 21, 22, 25, 27, 28, 30.5, (34)Surface Treatment: Titanium CoatingCobalt High Speed SteelCutting OilScrewdriver bit