Features:* High hardness, unique stepped structure, the drill bit can open a hole of different sizes.* Suitable for those works whose hardness is lower than 25 degrees and the thickness is 4mm or more, such as aluminum parts, insulation board, pvc board, etc.* Central blow is not needed, small shaking, difficult to break.* Used with pistol drill or bench drill, Water it to cool down during operation, to prolong its service life, the proper drilling speed is 250-400 rpm.* Widely used for cutting holes in various materials, such as steel, wood, thin iron, aluminum alloy, etc. Specification:Product Name: Step Drill Material: HSSOSurface Treatment: Black NitridingColor: BlackSize: As the picture Groove: Spiral Shank Type: 6.35mm(1/4 Inch)5 Steps: 4, 6, 8, 10, 12mm15 Steps: 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32mm Suitable for: Cutting holes in various materials, such as steel, wood, thin iron, aluminum alloy, etc. Quantity: 2pcs/setPackage Contents:1 × 5 Step Drill 1 × 15 StepsNote:1. Transition: 1cm=10mm=0.39 inch.2. The actual colors of the item may be slightly different from the pictures shown on website caused by many factors such as brightness of your monitor and light brightness.3. Please allow slight manual measurement deviation for the data.