Drill America 29 piece 135 degrees split point heavy duty drill bit set comes in a metal case. Manufactured to National Aerospace Standard 907, these drills are self-centering and reduces thrust. Ideal for portable or machine drilling. Short, rugged construction performs well in a broad range of materials in the iron and steel families. Screw machine drills are popular in the automotive and construction industries. They are often used in screw machine set-ups where spindle clearance is limited. Sizes smaller than #52 have the 118 degrees standard point. 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. Gold oxide is a thinner oxide surface treatment than black oxide typically used to identify cobalt steel tools; performance is similar to uncoated tools. Round shanks allow use with a wide variety of toolholding systems. When run in a counterclockwise direction (right-hand cut) spiral fluted tools evacuate chips up and out of the cut to reduce clogging. Set include fractional sizes: 1/16" to 1/2" (1/64 Increments).