A drill bit with a housing and roller cones has a high-speed fluid jet erosion system utilizing dual discharge, high-velocity, jet streams that is directed at the surface to be eroded. The jet streams are developed from a dual discharge nozzle adapted to form a first, swirling liquid jet and a second,...http://www.google.es/patents/US5862871?utm_source=gb-gplus-sharePatente US5862871 - Axial-vortex jet drilling system and method
