Hymnorq 116 Inch to 14 Inch 13PC M35 Cobalt Steel Jobber Twist Drill Bits Set135 Degree Split Point Metal Index Case Extremely Heat Resistant for Stainless Steel and Cast Iron

M35 Grade Cobalt Steel Cobalt drill bits are not made of pure cobalt, but rather a steel alloy with certain percent cobalt. The 5-percent alloy is known as M35 grade. The cobalt increases the strength of the steel and makes it more heat-resistant. For Drilling Stainless Steel This set of M35 cobalt steel drill bits are particularly successful in cutting through hard metals such as stainless steel and cast iron, although they can be used for softer materials, too. 135 Degree Split Point The flater the drill, the smaller the chip width. This means less force required to remove metal, compared with lower angles like 90° and 118°. This is important on hard stuff, because your power requirements are already more than mild steel, so making the chip load less helps. It also reduces heat since less surface area is generating the cut. Lowest Cost Per Hole Drilled Cobalt drill bits are more expensive than other drill bits, but if you regularly drill through metal, they are a good investment since they tend to last longer. With an extended tool life, Hymnorq cobalt drill bits will give you the lowest cost per hole drilled. Not Suggested for Hardened Steel, High Carbon Steel and Steels Blended with Impurities M35 grade cobalt drill bits are NOT suitable for hardened steel, high carbon steel and heat-treated steel by the experiences of some customers. Cooling Liquid Required Please use with cooling liquid to prolong the working life of the drill bits and to avoid overheating and breakage. About Breakage Please be careful when you drill holes with those needle-like small bits like 1/16". They're more likely to break than larger ones. BUY WITH CONFIDENCE: If you're not completely satisfied with the product quality, please contact us. Refund or free replacement.