Coated tool has characteristics as high surface hardness, good abrasion performance, stable chemical properties,small friction factor and lower thermal conductivity,etc.The cutting performance is 30% higher than non-coated tool.Promote grade 0.5-1 of processing accuracy.Prolong the gun drill's service life and lower 20%-50% of tool's consumption cost.The normal coating contains TiN,TiAIN titanium based coating and AlCrN chromium based coating,etc. 

 Gun drill repreasents the advanced and efficient hole processing technologies. It is not only used to process deep holes( ratio of depth to diameter is more than 10), but used to process precision shallow holes. It consists of drill stock, drill stem and drill bit which are all welded together. The hole in the middle is the channel through which the cutting fluid enters the cuttng area and the chips are removed outside by a V-shaped groove