Accurate center holes can be drilled in metal processing, which is very useful for starting holes of larger drills. It can be used with lathes and most electronic drills to drill holes in steel, iron, alum, carbon steel, brass and other tough materials with hardness of 170HB to 200HB. Spiral groove is helpful to remove chips and debris from the drill bit, reduce friction and heat, and realize faster and cooler drilling process. Precision grinding is - to achieve better use effect and prolong service life. The center drill is made of HSS, with extremely blades, low consumption, durability, impact resistance and wear resistance. Name:center drill Quantity:7pcs Colour:Gold & Silver Material:high speed steel Size:1.0/1.5/2.0/2.5/3.5/4.0/5.0(mm) Package Contents: 7 * center drill Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.