Application October 8, 1956, Serial No. 614,402 4 Claims. (Cl. 255-4) The present invention appertains to improvements in well drilling apparatus wherein mud or other fluid is pumped down through a hollow drill stem to operate a hydraulic turbine unit for driving the drilling bit and to wash the cuttings and particles upwardly to the surface, while, at the same time, shoring up the walls of the we