Tail pipe milling gets through usefulness stifled milling instrument of preventing spraining

The utility model relates to a many sets of pressure system well tail pipe milling get through technical field, in particular to tail pipe milling gets through usefulness stifled milling instrument of preventing spraining. The top connection is connected to the device's junk mill body upper end, and junk mill body lower extreme welding YD granule carbide welding rod is provided with the spring in the junk mill body and the top connection, and the spring upper end is provided with the steel ball, and the steel ball seals the joint central passage through the spring. The utility model discloses a when running the drilling tool into the well the operation, prevent the drilling fluid backward flow, prevent the bushel iron bits to get into the drilling string, play and prevent spraining stifled effect, simple structure, repeatedly usable, safe and reliable, it is stifled effectual to prevent spraining, shortens construction cycle. Having overcome current milling instrument when running the drilling tool into the well, having caused easily that the drilling tool is intraductal sprains stifledly, construction cycle is long not enough.