6pcs Combined Center Drill Countersink Bit Lathe Mill Tackle Tool Set Kit Features: Durable and Resistance: Center drill bit is made of HSS high-speed steel, with an extremely sharp blade, low consumption and durable with impact resistance, wear resistance. 60 countersink angle fits all standard centers. Wide Usages: Center drill bits can be used to make conical holes for a lathe center in order to make a starting point for a standard drill, designed to prevent the drill from walking, as well as for producing center holes in components or Workpieces with requiring machining between centers. Available for all Kinds of Materials: Metal, Alloy, Copper, Iron, Wood, Aluminum, and so on. Specification: Each drill has a double end and is ground with a standard 60 degree angle The set includes 1 each of the following sizes: 1 with 4mm body diameter & 1mm drill tip diameter 2 with 4mm body diameter & 1.5mm drill tip diameter 3 with 5mm body diameter & 2mm drill tip diameter 4 with 6mm body diameter & 2.5mm drill tip diameter 5 with 8mm body diameter & 3mm drill tip diameter 6 with 12mm body diameter & 5mm drill tip diameter Instructions: Choose a match type of center drill bits according to the hole type and the straight hole size of the machined parts. The heat treatment hardness of center drill bit is between 63-66HRC appropriate. Wash the rust-proof grease before using the center drill bit, so as to avoid chip sticking on the cutting edge. The surface of work-piece should be smooth to avoid center drill bit being damaged. The center drill bit should achieve the required position accuracy before drilling. Package Included: 1 set of 6pcs HSS Center Dril