10Pcs Twist Jobber Drill Bits 8.5Mm Nitride Coated High Speed Steel (Hss) 4241

4241 high-speed steel provides excellent hardness, high strength, wear resistance and good heat resistance. This helps ensure efficient, consistent drilling performance, and prevent overheating and extending the life of the drill bit. Black nitride coating can improve hardness, increase wear resistance and prolong its life. The nitride coating also reduces friction in the drilling process, resulting in smoother and faster drilling performance. The 135 degree fast cutting point penetrates quickly with less pressure and prevents walking on metal surfaces. Jobber drill bits can drill clean and accurate holes in stainless steel, cast iron, carbon steel, aluminum alloy, copper, and brass, wood and plastic. Large spiral grooves facilitate the export of metal chips, saving time an effort. NOT suitable for tiles, concrete, walls, stones. The twist drill bit can be used with handheld drills, drilling machines, bench drills, machining centers, CNC lathes. Use an appropriate lubricant (such as cutting fluid or oil) to reduce friction and heat build-up. Make sure the drill bit is tightened securely, and keep the drill bit perpendicular to the work surface. Note: The larger the diameter, the slower the speed required. Start the drill at a slow speed and gradually increase to the desired drilling speed. If the hole is larger than 6mm, first drill a small hole with a 3.2mm-4mm drill bit, and then use a larger drill bit to enlarge the hole.