Our Center Drill Bit Set features a wide range of sizes, high-speed and solid construction, and 60-degree angle for accurate center holes. Made of premium quality high-speed steel, this set can be used with lathe machines and electronic drills to work with tough materials. Tips are also included for best use. Features: 1. Wide Range of Sizes Optional: Cutting Diameter x Length: 1 x 33mm, 1.5 x 33mm, 2 x 40mm, 2.5 x 44mm, 3 x 70mm, 4 x 70mm, 5 x 70mm optional, to meet different needs. 2. Accurate: The 60-degree angle center drill is very useful in drilling accurate center holes, 60-degree countersink holes, or starter holes for bigger drill bits in metal-working. 3. Premium Quality: Our center drill bits are made of high-speed steel, solid and high-temperature, and wear-resistant. 4. Widely Applicable: Can work with lathe machines and most electronic drills to drill holes in Steel, Iron, Alum, Carbon Steel, Brass, and other tough material ranging from 170HB up to 200HB. 5. Tips For Using Center Drill Bits: Fix the work piece deep in the Lathe machine to prevent wobbling when rotate. Get rid of the acid surface before drilling and use oil or proper lubricant to protect the bits. A good rule to follow is to go 2/3 deep on the tapered section. Stop immediately if the drilling sound is abnormal and fix any problem before resuming. Clean the center drill bits before and after drilling, and apply oil to store it properly. Specification: Material: High Speed Steel Color: Silver Product Size: Cutting Diameter x Length: 1 x 33mm, 1.5 x 33mm, 2 x 40mm, 2.5 x 44mm, 3 x 70mm, 4 x 70mm, 5 x 70mm Product Weight: 2g, 3g, 5g, 7g, 12g, 19g, 30g Package Included: 1 x Center Drill Bit