Abstract: Hard metal cutters have the attachment portion of their axial length which is cylindrical in cross section, mechanically secured by a transition fit within cylindrical sockets provided in a suitable steel body, such as, for example, a rock drill bit; the cylindrical sockets contain a local circumferential band of deformed and compressed metal axially spanning the innermost cylindrical boundary of the maximum hard metal diameter upon assembly. This eliminates detrimental tensile stresses due to assembly; and provides a region of high compressive stress to reduce the effective fatigue loads during drilling.

Abstract: According to a depicted embodiment thereof, the novel threaded engagement means comprises a drill rod coupling which is centrally bored and threaded to receive threaded drill rods. A stack of apertured discs, however, engages and lines the threaded bore. The discs intimately engage, and bridge between, the coupling and drill rod threads, and communicate torque therebetween. The coupling has a bearing surface or land upon which the discs are supported, and a retainer set in a recess formed in the coupling secures the disc stack in place.

Abstract: According to a depicted embodiment thereof, the novel earth bit comprises a shank having a threaded end and a bit head centrally bored and threaded to receive a shank. A stack of apertured discs, however, is interposed between the threaded bore or cavity in the bit head and the threaded end of the shank. The discs intimately engage, and bridge between, the shank and bit head threads, and communicate torque therebetween. The bit head cavity has a bearing surface or land upon which the discs are supported, and the shank has an annular shoulder which bears upon the stack and, thus, compressive forces are communicated from the shank to the bit head. The bit head, of the invention, then, comprises the aforesaid bit head, having the stack of discs secured therein by a retainer, for use, in a plural-part earth bit having a threaded shank.

Abstract: According to a depicted embodiment thereof, the novel earth bit comprises a shank having a threaded end and a bit head centrally bored and threaded to receive a shank. A stack of apertured discs, however, is interposed between the threaded bore or cavity in the bit head and the threaded end of the shank. The discs intimately engage, and bridge between, the shank and bit head threads, and communicate torque therebetween. The bit head cavity has a bearing surface or land upon which the discs are supported, and the shank has an annular shoulder which bears upon the stack and, thus, compressive forces are communicated from the shank to the bit head. The bit head, of the invention, then, comprises the aforesaid bit head, having the stack of discs secured therein by a retainer, for use, in a plural-part earth bit having a threaded shank.

Abstract: The stabilizer, according to a preferred embodiment thereof, comprises a generally tubular body which is axially slit, according to the prior art. According to the invention, the surfaces of the body immediately adjacent to the slit have ribs formed thereon which define bearing surfaces for clamping together, to draw the surfaces together, closing the slit, and thereby contract the stabilizer to facilitate its insertion into an undersized bore. The novel method, then, comprises contracting an axially slit friction rock stabilizer by engaging the aforesaid ribs (formed thereon) with a tool, to contract the stabilizer to a reduced and constrained cross-sectional dimension, inserting the stabilizer into an undersized bore, and releasing it therein, in order that it may engage and stabilize the surface of the bore (of the earth structure).

Abstract: The stabilizer, according to a preferred embodiment thereof, comprises a generally tubular body which is axially slit, according to the prior art. According to the invention, the surfaces of the body immediately adjacent to the slit have ribs formed thereon which define bearing surfaces for clamping together, to draw the surfaces together, closing the slit, and thereby contract the stabilizer to facilitate its insertion into an undersized bore. The novel method, then, comprises contracting an axially slit friction rock stabilizer by engaging the aforesaid ribs (formed thereon) with a tool, to contract the stabilizer to a reduced and constrained cross-sectional dimension, inserting the stabilizer into an undersized bore, and releasing it therein, in order that it may engage and stabilize the surface of the bore (of the earth structure).