Sutton Tools Heavy Duty Cobalt jobber drills are industrial quality drilling materials that have high hardness and tensile strength such as cast iron, bronze, hardened steel & stainless steel. The 5% cobalt formula improves abrasive & heat resistance, for increased strength at higher cutting temperatures. Crafted with durability and precision in mind, these cobalt drill bits are engineered to withstand heavy-duty use, making them ideal for professional tradespeople and DIY enthusiasts alike.