A milling device for cutting up road surfaces which includes a roller-type milling body including a rotatably-mounted spiral conveyor, a plurality of rotary cutters carried on the spiral conveyor, the rotary cutters mounted for free rotation about their respective longitudinal axes. A plurality of retaining boxes is provided, each retaining box detachably connected by at least one screw in a respective trapezoidally-shaped positive radial recess in a wall of the spiral conveyor, each retaining box having a bore hole therein for receiving a respective one of the rotary cutters. The retaining boxes each have a trapezoidally-shaped shaft part for being matingly received in the trapezoidal recess with the narrow side of the trapezoidally-shaped shaft facing towards the spiral conveyor.

An edge cutter bit assembly for use in conjunction with a rotatable drum having an edge. The edge cutter bit assembly includes a holder that includes a plurality of bores wherein each bores carries a chisel cutter bit so that the chisel cutter bit is non-rotatable. The holder is oriented with respect to the drum so that at least a portion of each one of the cutter bits extends past the edge of the drum.

A multi-bladed reaming apparatus for enlarging a subterranean borehole, the apparatus having a tubular body with a plurality of longitudinally-extending, circumferentially-spaced, generally radially-extending blades carrying cutting elements, the blades being unequally spaced about the body. The cutting depth of the cutting elements on at least one of the blades is adjusted to modify the distribution of the depth of cut (DOC) among the cutting elements to substantially equalize the volume of formation material removed by the blades. Wear is reduced and the potential for premature failure of cutting elements on any single blade is alleviated.

Drill bit cutters and drill bits equipped with the cutters. The cutter is mounted on a bit to present the formation with a radiused, curving, side wall cutting face that is concave in one dimension and convex in another dimension. In a preferred form, the cutting face is in the form of a portion of a surface of revolution generated by an arc segment that is concave relative to the axis of revolution. The cutting face is formed on a layer of polycrystalline diamond disposed on a substrate of tungsten carbide. In another side wall cutter arrangement, a standard cylindrical cutter with a diamond cap is mounted to present the curved cylindrical side of the cap to the formation. Curved side wall cutting faces cut more efficiently than the usual flat end face of conventionally mounted cutters. A major portion of the diamond volume in a side mounted cutter trails the point of cutting face engagement with the formation to provide impact resistance and an increased diamond wear area. The radiused face cutter may be mounted in any orientation on the bit. When mounted conventionally, such that the axis of the cutter is inclined away from the bit and into the direction of bit rotation, the cutter end surface rather than the side wall cuts the formation. In this orientation, the rake of the cutter may be increased to place a second cutting surface into engagement with the formation to provide two cutting surfaces.