Hard alloy is generally used in drilling bit of Chinese printing plate, because epoxy glass cloth clad copper foil plate can wear tool very fast. The so-called cemented carbide is made by pressing and sintering tungsten carbide powder as matrix and cobalt powder as binder. It usually contains 94% tungsten carbide and 6% cobalt. Because of its high hardness, high wear resistance and certain strength, it is suitable for high-speed cutting. In order to improve the properties of cemented carbides, a layer of 5-7 μ m hard titanium carbide (TIC) or titanium nitride (TIN) with a thickness of 5-7 μ m is used to improve the properties of cemented carbide. In some cases, titanium, nitrogen and carbon are implanted into the matrix to a certain depth by ion implantation technology, which not only improves the hardness and strength, but also migrates inward when the bit is reground. In addition, a layer of diamond film is formed on the top of the bit by physical method, which greatly improves the hardness and wear resistance of the bit. The hardness and strength of cemented carbide are related not only to the ratio of WC to CO, but also to the particle size of the powder. < br style = "list style type: none;" / > & nbsp; when the substrate stack is not high, the use of drill sleeve can avoid drilling deviation. At present, most of the manufacturers use the CNC plane drilling machine, and the CNC < span style = "list style type: none;" > plane drill < / span > uses cemented carbide fixed shank drill, which is characterized by automatic replacement of drill bit. High positioning accuracy, no need to use drill sleeve. Large helix angle, high chip removal speed, suitable for high speed cutting. In the whole length of the chip removal groove, the diameter of the bit is an inverted cone, and the friction with the hole wall is small, and the drilling quality is high. The common drill stem diameters are 3.00mm and 3.175mm. The average grain size of WC phase in cemented carbide bits with ultra-fine particles is less than 1 μ M. This kind of bit not only has high hardness, but also improves compressive and bending strength. In order to save cost, many drill bits adopt welded shank structure. The original drill bit is made of cemented carbide as a whole. Now the drill shank at the rear is made of stainless steel, which greatly reduces the cost. However, due to the different materials, the dynamic concentricity of the drill bit is not as good as that of the whole cemented carbide bit, especially in the aspect of small diameter. The types of drills for plane drills are straight shank twist drills, fixed shank twist drills and undercut bits. Straight shank twist drill is mostly used in single head drilling machine to drill simple printed circuit board or single panel. Now it is rarely seen in large circuit board production plants. Its drilling depth can reach 10 times of the drill diameter.