Rotary cone rock bit

A rotary cone rock bit 10 for use in earthen formations utilises diffusion type nozzles 30 which are located at the outer region of a dome portion 40 of the rock bit resulting in a diffused flow 42 of fluid without turbulence leaving the exit end 36 of the nozzle 30. The diffused spray 42 of fluid at a lesser velocity will better clean the rotary cones 22 by moving the fluid closer to the cones without erosive damage to the cones or loss of cutter inserts or milled teeth. The diffused spray will additionally cover a larger area of a borehole bottom resulting in better bottom hole cleaning.