Sutton Tools Heavy Duty Cobalt Jobber Drills are industrial quality drill bits made for drilling materials that have high hardness and tensile strength such as cast iron, bronze, hardened steel & stainless steel. These drill bits feature a thick core for increased rigidity in hard materials and made are made from HSS Co. which improves abrasive and heat resistance, for increased strength at higher cutting temperatures. These also have a 135 split point which enables accurate positioning and less drilling pressure, along with a precision engineered parallel shank for accurate hole size.