4PCS HSS Cobalt Stepped Drill Bit Set Practical Black Nitride Coated Metal Drilling Bits Kit for Thin Iron/Steel/PVC/Wood Panel

Features:
Made of superior high speed steel, firm and long-lasting.
Nitride coated, has nice heat resistance, corrosion resistance and rust resistance.
No need for a pilot hole, can automatically deburr holes as you drill.
Special step stucture, can drill different size of holes.
Working with water cooling, can effectively extend the service life of bit, drilling speed 250-400 recommended.
Apply to thin iron plate, steel board, wood, aluminum, insulation panels, PVC sheet, ect.