Abstract: A rotary drilling bit is provided which includes means for providing a protective stream of a high pressure fluid for its cutting edges fed parallel to the drilling axis directed perpendicular to the cutting edges. The drilling bit also includes means for providing a stream of low pressure fluid for flushing away pulverized rock cut by the drilling bit. The drilling bit is mounted on the end of boring tubing made up of a pair of coaxially positioned tubings, the innermost one supplies the high pressure fluid and the outermost one supplies the low pressure fluid. A drilling process which employs the drilling bit and boring tubing efficiently drills through both soft and non-abrasive rock and hard or abrasive rock.