I tested various cobalt bits against hard steel on my drill press. My "hard steel" sample is a used Woods mowing blade about 1/4 thick. Not only did this bit drill through the blade, it "won" my tests. Others, that cut through the blade were made by Irwin and Century. Two types of Milwaukee bits are non-drillable (still good for mild steel). I didn't test Dewalt because I can't buy 15/64 bits".