Abstract: This earth boring drill apparatus has a cutter mounting leg extending from one side of a drive stem and a removable cutter assembly, including a fixed shaft and cutter journaled for rotation on the shaft supported between the drive stem and the mounting leg. The stem has a bore for slidably receiving the inner end of the shaft. The cutter mounting leg terminates in an end surface extending parallel to the axis of rotation of the bore and shaft. A shaft supporting lug projecting from the outer end of the shaft has a surface which is parallel to the end surface on the leg. The opposed surfaces respectively have a V-shaped projection and mating groove which provide lateral alignment and prevent shaft rotation while permitting the shaft to be movable in an axial direction by an amount sufficient to permit the shaft to be withdrawn from the bore.

Abstract: A raise type of earth boring drill in which the cutter assembly is detachably secured to the drive stem to permit replacement of the stem. The stem slidably engages a central opening in the cutter assembly, the cutter assembly engaging a shoulder on the stem which carries axial loads in the drill. The cutter assembly is detachably anchored by a plurality of bolts to a torque plate attached to the end of the stem for transmitting torque load to the cutter assembly, the bolts clamping the cutter assembly against the shoulder.