A – Z Cobalt Steel Jobber Drill Bit Set 26 Pieces. Sizes: A – Z Cobalt drill bits are effective in drilling tough, high tensile strength materials. Display high red hardness, permitting speeds up to 30% greater than with conventional M2 high speed steel. 135° split point tip for fast penetration and accurate drillingSizes: A – Z Cobalt drill bits are effective in drilling tough, high tensile strength materials. 135° split point tip for fast penetration and accurate drilling.