Drill America end mill. Cobalt steel tools are similar to high-speed steel, but with more cobalt for improved performance when cutting harder metals such as stainless steel or nickel alloys. Weldon shanks feature a round shank with one of more flats machined into the side for easy indexing and alignment. When run in a counterclockwise direction (right-hand cut) spiral fluted tools evacuate chips up and out of the cut to reduce clogging. 4 Flute double end.