Description:Spiral Stepped Drill 4-20mm Hex Shank Nitrided Conical Cone Drill BitsHigh hardness, unique stepped structure, a drill can open a variety of size aperture.Suitable for these work-pieces that hardness is lower than 25 degree and the thickness is below 4mm, such as aluminum parts, insulation board, PVC plate, etc.The central punch is not needed, small shaking, hard to be broken.Used with pistol drill or bench drill, water it to cool while working to prolong its life.Specification:Material: HSS(High Speed Steel)Shank Type: Hex ShankType: Spiral GroovedSurface Treatment: Nitriding blackStep Diameter: 75mm/2.95inchPackage Includes:1 Piece 4-20mm HSS Hex Shank Spiral Step DrillNote:We suggest customers to use cutting fluid to keep the bits cold during usage to avoid step drill bits become overheated and get burned up due to fast rotary friction.