A drilling bit, such as a crenellated drilling bit for fluid-jet supported rotary drilling in rock comprises a nozzle for directing a jet of high-pressure fluid against rock material being bored. In addition to transporting away rock chips, the jet penetrates fissures in the rock and supports the breaking down of the rock structure by the drilling bit. Since such nozzles tend to wear more rapidly than the cutting edges of the drilling bit, a readily exchangeable nozzle insert is provided. The no...

A drill bit for drilling bore holes in underground formations comprising a bit body with a connecting spigot for connecting to a drill string or the like, and a cutting head which comprises a circumferential face extending parallel to its longitudinal axis and an end face having a drilling axis which is aligned with the axis of the connecting spigot. The drilling axis is parallel to and is offset relative to the axis of the cutting head. It is preferred that the end face is, at least in part, co...

A downhole impact drill having a drill bit head with a drill bit sector for drilling an enlarge hole upon rotation of the drill. The bit is mounted within a chuck for movement between a retracted, working position in which the bit is coaxially mounted for drilling and an extended, non-working position in which the bit is loosely mounted within the chuck to permit the bit to swing laterally to reduce the diameter of the drill bit head envelope. In its extended, non-working position, the bit is su...

A drill bit for use in combination with a through-the-steel drill stem, the drill bit including an elongated body portion having a bore through which cuttings may be removed, a web extending transversely across the bore for receiving a drill tip, and drill ports leading from the drill tip to the bore and from the periphery of the body portion to the bore, the drill ports comprising opposed axially extending openings contoured as a hemisphere to define opposed axially extending faces of the web a...

A drill bit the point of which has two or more outer cutting edges and is formed with a V-shaped notch. The V-shaped notch has its center lying on the axis of rotation of the drill bit and opens in the direction of feed of the tool. The V-shaped notch defines inner cutting edges terminating in respective outer cutting edges.

A tool such as a drill has a cylindrical shank for insertion in a tool holder of a rotary percussive or other rotary machine, such as a drilling machine. The shank has a first surface extending transversely of the shank from a point of intersection with the periphery thereof and a second surface extending from the first surface at the end of the first surface remote from the point of intersection of the first surface with the periphery of the shank to a point of intersection with the periphery s...

A bit holder for a replaceable bit is disclosed. The bit is of the type having a pointed head portion axially extending from a shaft portion. The bit holder has a holder part for receiving the bit and has a base part for securing to a cutter head. The bit holder part is releaseably secured to the base part for easy replacement. The holder part has at least one reaction surface cooperating with one reaction surface on the base part for counteracting forces arising on the bit while cutting. A bolt...

An improved drill bit and a method for making the same. A body having an upper end is adapted for connection to a source of rotary motion. A curved surface formed on the lower end of the body includes a plurality of cutting elements embedded therein. A port provides drilling fluid between the curved surface and the bore during drilling. The cutting elements and fluid courses formed on the curved surface define a gap between the surface and the bore during drilling. The gap is formed to provide n...

A drill bit, particularly for cutting deep holes in hard materials, includes a tubular shank with a solid center and diametrically opposed coolant conduits which supply coolant to a tungsten carbide tip located on one end of the tubular shank. Swarf and debris are carried by the coolant away from the cutting area and along swarf clearance channels located along the exterior of the shank tube out of the borehole. The carbide tip is brazed to the tubular shank and is formed with a pair of angularl...

A drill bit is provided with a pair of cutting edges which are positioned so that a narrow slot is formed therebetween in an area including the rotational axis of the drill bit and so that the lines joining the rotational axis of the drill bit and the innermost points of the respective cutting edges are at an angle not larger than about 160.degree. with each other as viewed in the axial direction of the drill bit.