Indexable type inner-cooling milling cutter capable of producing supersonic speed low temperature airflow

The invention discloses an indexable type inner-cooling milling cutter capable of producing supersonic speed low temperature airflow. The inner-cooling milling cutter comprises a cutter holder, a cutter bit, a shrinking-expanding nozzle and indexable blades, wherein the cutter holder is connected with the cutter bit, two indexable blades are fixed on the cutter bit in central symmetry, the upper end of the cutter bit is provided with an inner-cooling hole matched with the indexable blade position, the inner-cooling hole is connected with the shrinking-expanding nozzle, two inner-cooling holes are respectively connected with sub-runners, the center of the cutter holder is provided with a cooling hole, the cooling hole is connected with a main runner, the main runner penetrates through the interior of the cutter holder and is communicated with two sub-runners; the continuous acceleration of the airflow in the nozzle can be used for obtaining the supersonic speed airflow, and meanwhile, the temperature is rapidly reduced so as to obtain the supersonic speed airflow at a low temperature for the low temperature cooling in the cutting processing.