High-speed steel, also known as HSS, is the most common drill bit for metal applications. It incorporates an element with cobalt that makes the drill bits harder than a typical HSS bit and thus suitable for precision drilling in stainless steel and other hard materials. The cobalt blend gives these bits a much longer life? 135-Degree Split Point & Twist Design? The split point design increases the cutting edge on the tip, and the blunter 135° angle means more of the cutting edge touches the surface sooner. The grooves on the sides of the bits’ twisted shanks will bring metal shavings up and out of the hole as you drill. ? Perfectly suitable for drilling hard metal such as stainless steel, cast iron, high temperature alloy, titanium alloy. Moreover, they can also be applied to cutting duroplasts, wood and some other soft materials. Drill bit holder with size index for easy induction and arrangement, and a portable metal case are both included. ? Twist drills are indicated in sizes. Assortment comes with a combined 29 sizes added:1/16″e;, 5/64″e;, 3/32″e;, 7/64″e;, 1/8″e;, 9/64″e;, 5/32″e;, 11/64″e;, 3/16″e;, 13/64″e;, 7/32″e;, 15/64″e;, 1/4″e;, 17/64″e;, 9/32″e;, 19/64″e;, 5/16″e;, 21/64″e;, 11/32″e;, 23/64″e;, 3/8″e;, 25/64″e;, 13/32″e;, 27/64″e;, 7/16″e;, 29/64″e;, 15/32″e;, 31/64″e;, 1/2″e;? Operation Technique & Tip? When drilling a hole with a cobalt bit, add a drop of oil on the metal to keep the cutting edge cooler as it cuts. You also want to consider placing some wood underneath the steel if possible. This lets you cut cleanly through the material and not strike a surface below which might dull the cutting edge. Tip:Please keep the bit perpendicular to the mateial during operation to prevent it from breakage.