Straight Groove Step Drill Bit Set, Titanium Coated Wood Metal Hole Cutter Core Applies to:Products are used in automotive processing, aerospace, sheet metal processing,Installation and maintenance of electrical and other industries,Work at heights with hand drills and other tools. Features :1. Unique stepped structure, a variety of standard size drill bits for engraving apertures, a box of ladder drill bits.2. Do not use center punch, easy to break, suitable for step drill specifications.3. Deburring, chamfering, expanding oval hole4. The swing is small, and a beautiful aperture can be carved without center punching.5. Surface treatment: Titanium size:5-step drill: 4-12mm (4mm, 6mm, 8mm, 10mm, 12mm)9-step drill: 4-20mm (4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm)10-step drill: 3-12mm (3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm)