LARGE DIAMETER BIT WITH BRIDGE MOUNTED DRIVE STEM

摘要

LARGE DIAMETER BIT WITH BRIDGE MOUNTED DRIVE STEM A drill bit is shown for enlarging a pilot hole into a larger diameter hole by disintegrating the earth formations that surround the pilot hole. The bit includes a cutterhead with a multiplicity of saddles containing rolling cutters for contacting and disintegrating the formations that surround the pilot hole. The rolling cutters are mounted so that the cutter face profile of the cutters extends in a uniform manner to the edge of the pilot hole and eliminates uncut bottom. A drive stem or stinger projects from the cutterhead. The lower portion of the drive stem or stinger comprises extensions that reach over or "bridge" the inner legs of the center saddles and extend into the available vacant areas between the saddles for attachment to the body of the cutterhead.