Abstract: A rotary drill bit for producing a raise bore about a pilot hole comprises a drill head having an upper surface for mounting cutter assemblies and lower surface spaced from said upper surface. The upper and lower surfaces are secured to and connected by a body sub. A drive stem is removably secured in the drive sub. The drive sub and stem have mating tapered portions for a press fit. Either the sub or the stem is provided with a spiral groove through which oil is injected under high pressure to expand the sub while the stem is rammed into place under high pressure. The stem can be removed by application of oil pressure and a ram force in the opposite direction.

Abstract: An earth boring auger having a shaft and helical flights thereon and a plurality of disc cutters mounted below the flights to engage the formation before it is engaged by the flights.