Large diameter drill bit

A large diameter rotary drill bit comprising:

• a main bit body adapted for connection with a dual-string drill column, said dual-string drill column consisting of a first outer drill pipe and a second concentric inner drill pipe spaced from said outer drill pipe, said body forming a central opening in communication with said second inner drill pipe of said dual-string drill column,
• means to confine a supply of drilling fluid directed through said drill column outwardly to a peripheral edge of said bit body, said drilling fluid subsequently being directed along at least one arcuate flow path from said peripheral edge to said center opening formed in said bit body, a first wall member mounted to a lower surface of said bit body, said first wall member being mounted substantially 90.degree. to said lower surface of said bit body, forming a first side of said arcuate path, and a second wall member substantially parallel with said first wall member mounted to said bit body forming a second enclosing side of said arcuate path, and
• a plurality of cutter assemblies rotatably mounted to said lower surface of said bit body within said first and second wall members, said plurality of said cutter assemblies being strategically positioned along said arcuate flow path to form a cutting plane for contacting and disintegrating an earth formation, said drilling fluid serves to direct detritus material along said at lest one arcuate path and to clean and cool said plurality of cutter assemblies during operation of said bit.