21 Piece Cobalt Drill Bit Set. Sizes 1/16" - 3/8" x 64ths (1/16", 5/64", 3/32", 7/64", 1/8", 9/64", 5/32", 11/64", 3/16", 13/64", 7/32", 15/64", 1/4", 17/64", 9/32", 19/64", 5/16", 21/64", 11/32", 23/64" and 3/8") . M35 5% cobalt drills are manufactured to Aerospace Standard 907. These cobalt drill bits display high red hardness, permitting speeds up to 30% greater than with conventional M2 high speed steel, and are especially effective in drilling tough, high tensile strength materials like stainless steel, inconel, and titanium. The 135 split point is self-centering and reduces thrust. Sizes smaller than 1/16 or #52, and larger than 1/2 have the 118 standard point.