Reverse circulation drilling system with hexagonal pipe coupling

摘要: A reverse circulation, pneumatic drilling assembly (10) wherein the bit is operatively connected to a dual wall pipe (12). supply of compressed air conducted through annulus (20) (12) down hole hammer (13). Exhaust from (13) directed for continuous removal debris central evacuation tube (43) Sections are joined by hex head couplings (180, 182) which quickly and easily engaged disengaged.