Cobalt Drill Bit Set 1/4" - 13PCS, M35 Twist Drill Bits Straight Shank, 1/4" High Speed Steel Drill Bits for Drilling in Hard Metal, Stainless Steel, Cast Iron

Suitable for drilling stainless steel, hard metal, aluminum, copper, plastic and hardwood. The 3-step design enables accurate centering, suitable for woodworking operations requiring precision drilling. In addition, the cobalt design allows it to perform better in hardwood boreholes. Control the bit speed from 200 to 1000 RPM, making it easier to drill in stainless steel. High RPM does not improve drilling efficiency, but rather increases the heat between the bit and the workpiece, which may cause the bit to soften and the workpiece to harden. Drill bit diameter ?5mm, speed (1000~700)5-10mm, speed (700~350)10-15mm, speed (350~200) use cutting fluid to make the drill bit more durable. Stainless steel tapping oil or engine oil is added to prevent the stainless steel from overheating and forming a very hard oxide layer.