[UPGRADED] Titanium Spiral Grooved Step Drill Bit Set & Automatic Center Punch, High Speed Steel, Double Cutting Blades Design with Aluminum Case 5-Piece Set Total 50 Sizes AUTOMATIC CENTER PUNCH -- Delivers an automatic, high-impact, spring-loaded strike through adjusting the cap. With the carbide tipped bit, the center punch is 10 times stronger than normal one 50 SIZES IN 5 -- The bit set includes five standard step drill bits that can replace 50 individual drill bits,processing 50 different kinds of diameter holes with the five pieces,without wasting time by changing drill bits. With spiral grooved design,they provide better orientation and make cutting more smoothly SPIRAL GROOVED DESIGN -- Povided better orientation and more smooth cutting for you. Its brass body has a deeply knurled surface for nonslip control HIGH SPEED STEEL -- Make it last longer than others and can automatically deburr holes while drilling to keep the drill bit clean.With titanium coating, its durability has been enhanced by reducing the friction and extending lifespan, which ensures easily cut through steel sheetsaluminum sheetscopper & plastic & wood board and many other types of sheet metal DOUBLE CUTTING BLADES & THREE-SIDED SHANK -- Double cutting blades and X-type openings design ensures a faster and smoother cutting; and 3-sided shank design prevents slipping in drilling chuck