Grooved Step Drill Bit: This drill bit is composed of industrial high-speed steel and a cobalt coating, possessing durability and strength. It can provide outstanding durability and maintain sharpness even when faced with demanding tasks. The cobalt coating increases wear resistance and minimizes friction to a great extent. The coated step drill bits are highly suitable for quickly drilling holes in aluminum, wood, copper, stainless steel, plastic and other metal sheets. Grooved Design: drill bit for metal is designed with two-flute . which can deburr chips faster and smooth drilling holes. drill bits have 118 split point tip, which can accelerate cutting speed and while preventing angled walking away from center. drill long-lasting and efficient. Wide Range of Applications: This step drill is suitable for drilling holes in types of sheet metals including plastics, aluminum, wood, and iron. (It is recommended to add coolant when drilling metal sheets, and the speed should not be too high.) This step drill bit is appropriate for home DIY enthusiasts, handymen, and professionals. Set Includes: The cone drill bits set includes 3 common sizes for versatility. Bit #1 (5 steps): 4mm, 6mm, 8mm, 10mm, 12mm; Bit #2 (15 steps): 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm, 30mm, 32mm; Bit #3 (9 steps): 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm. Specification:C:HSS4241 Spiral Colour:As Shown Material:High Speed Steel Package Contents: 3pcs x Step Drill Bit Set Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.