An insert cutter for an earth boring machine that functions to form a plurality of circular kerfs in the earth formations being bored thereby fracturing the portion of the formations between a proximate pair of kerfs and causing fragments of the formations to be separated from the formations being bored. A multiplicity of annular rows of tungsten carbide inserts are positioned in the cutter body thereby simulating the formation loading of a disk cutter. Each insert has an elongated formation contacting head and all of the heads of the inserts in an annular row are aligned. An annular row of inserts functions to form a circular kerf in the earth formation being bored as the cutter is moved along the formation. The cutting structure interruption (C.S.R.) in an annular row of inserts is less than the pitch cord (P.C.) of the annular row.

A roller cutter assembly comprising a cutter hub adapted for rotation with respect to a rock face and having a peripheral surface with an axially extending width. The first cutter ring is located on the cutter hub. A second cutter ring is also located on the cutter hub. Both the first cutter ring and the second cutter ring are adjustable between at least first locations and second locations along the width of the peripheral surface of the cutter hub such that reorientation of at least one of the first cutter ring and the second cutter ring on the cutter hub alters the axial spacing between the first cutter ring and the second cutter ring, resulting in alteration of the spacing of the cutters located thereon. Reorientation of the first cutter ring and/or the second cutter ring is accomplished by reversing the orientation of the one cutter ring with respect to the other, varying the number of spacers which locate and brace the first cutter ring and second cutter ring on the cutter hub, and/or varying the relative widths of the spacers.

An improved rolling disc type cutter, and novel cutterheads employing such cutters. The cutter includes a washer surface and a cutter ring assembly. The cutter ring assembly further includes an annular cutter ring with an interior annulus defining portion and an outer ring portion. A bearing assembly substantially fits into the annulus of the cutter ring in a close fitting relationship with the shaft, so that the cutter ring may rotate with respect to and be supported by said shaft. The bearing assembly includes a bearing and a seal which fits between the washer surface and the cutter ring to form a lubricant retaining seal for the interior annulus portion of the cutter ring. A retainer assembly is used to retain the cutter ring assembly on the shaft, and a cap seals the interior annular portion of the cutter ring assembly so that, in cooperation with the seal and the cutter ring, a lubricant retaining chamber is provided. This simplified cutter design is achieved by using a comparatively large stiff shaft which is preferably in the range of 40-50% of the cutter ring diameter. The stiff shaft design permits cantilever mount of the cutter on a cutterhead. The design allows increased loading of the disk cutter footprint, and permits single disc cutter technology to be applied to small bits or cutterheads. Also, hard metal cutting edge inserts with reduced leading and trailing edge surface curvature are provided.

An improved disc type rolling rock cutter, and novel cutterheads employing such cutters. A rock cutter with an improved, simplified structure, with compact bearing, and smooth, rounded blade shape is disclosed. The design incorporates a cutter ring, bearing assembly, and seal assembly. The cutter may be assembled and disassembled for rework by a single worker with simple hand tools. Replacement of worn out cutter rings is done quickly and easily by removing the old ring assembly and then sliding a new ring, bearing, and seal assembly on to the cutter shaft. This simplified assembly is achieved by using a comparatively large shaft which is normally in the range of 30-50% of the ring diameter. The shaft design is sufficiently robust to permit a cantilever mount of the cutter. The unique configuration allows 30,000 lbs. or more thrust to be applied to a 5 inch diameter miniature disc. This capacity permits single disc cutter technology to be applied to smaller bits or cutterheads than previously possible. Also, a unique method of shaping and installing hard metal inserts improves cutting efficiency over the life of the cutter, and increases wear life in highly abrasive conditions.

An improved disc type rolling rock cutter, and novel cutterheads employing such cutters. A rock cutter with an improved, simplified structure, with compact bearing, and smooth, rounded blade shape is disclosed. The design incorporates a cutter ring, bearing, and seal into a single cutter ring assembly. The cutter may be assembled and disassembled for rework by a single worker with simple hand tools. Replacement of worn out cutter rings is done quickly and easily by removing the old ring assembly and then sliding a new ring, bearing, and seal assembly on to the cutter shaft. This simplified assembly is achieved by using a comparatively large shaft which is normally in the range of 40-50% of the ring diameter. The shaft design is sufficiently robust to permit a cantilever mount of the cutter. The unique configuration allows 30,000 lbs. or more thrust to be applied to a 5 inch diameter miniature disc. This capacity permits single disc cutter technology to be applied to smaller bits or cutterheads than previously possible. Also, a unique method of shaping and installing hard metal inserts improves cutting efficiency over the life of the cutter, and increases wear life in highly abrasive conditions.