A hollow drilling tool is made up of an axially extending tubular carrier part, a cutting body at one end of the carrier part, and guide elements located in the axial direction of the carrier part between the cutting body and the carrier part. The radially outer surface of each guide element is in alignment in the axial direction of the carrier part with the radially outer surface of the cutting body. The guide elements guide the hollow drilling tool in a borehole formed by the cutting body.

A drill bit sub, which has a drill bit with three equally angularly spaced cutters releasably threaded into its bottom surface, has its lower portion reduced in diameter. A collar is welded to the uppermost portion of the lower portion of the drill bit sub and has its lower surface formed at an angle to its longitudinal axis. A protective sleeve, which is a hollow cylindrical metal tube, is removably mounted on the lower portion of the drill bit sub and has its upper surface at the same angle as the lower surface of the collar. The protective sleeve has three equally angularly spaced wear strips, which are substantially aligned with the three cutters on the drill bit. A first break out ring is mounted between the bottom of the protective sleeve and a support surface on the drill bit so that the drill bit bears against the bottom of the first break out ring. The drill bit sub has its upper portion, which is beneath its threaded upper end threaded into a threaded receptacle in a lowermost drill section of the drilling tool, reduced to receive a second break out ring.

A drill bit used for obtaining core samples in concrete or rock formations. The drill bit comprises a cylindrical body having a generally annular-shaped cutting surface at one end and at least one waterway including an inner channel on the interior surface of the body extending to the cutting surface and an outer channel on the exterior surface of the body extending to the cutting surface at a point radially spaced from the point where the inner channel extends to the cutting surface. The waterway further includes a recessed portion on the cutting surface connecting the inner and outer channels at the points at which the channels respectively extend to the cutting surface. Such a waterway helps to wash the cutting surface of the bit so that concentration of drill cuttings on the cutting surface is minimized.

This invention is directed to a stabilizer-reamer which is useful in drilling oil wells and holes in mineral formations. The stabilizer-reamer extends the life of the drill bit by maintaining the diameter of the hole to original specifications. The stabilizer-reamer comprises a stabilizer portion which reduces excessive lateral movement of the drill bit, a reamer portion which reams away undersize portions of the walls of the hole and a rock chip grinding portion which breaks down oversize rock chips in the hole.

A drill section includes a hollow tube having a reduced portion of a box disposed in each end. Each box is welded to the hollow tube by a circumferential weld extending around an angled portion connecting the reduced portion of the box to a portion of the box having the same outer diameter as the hollow tube. There preferably is welding of the reduced portion of the box to the hollow tube through three equally angularly spaced slots at each end of the hollow tube. A break out ring is disposed on a threaded pin of a tool joint between the box, which has a threaded recess extending inwardly from its end to receive the threaded pin to attach the tool joint to the box, and an annular surface of the tool joint. A protective sleeve on the box has an annular end surface at the same angle to its longitudinal axis as an annular end surface of a collar, which is welded to the box, and held thereagainst by the tool joint attached to the box. One tool joint has a threaded recess, and the other tool joint has a threaded pin, which extends into the threaded recess of the tool joint of the drill section above it while the threaded recess in the tool joint receives the threaded pin of the tool joint of the drill section beneath it or the threaded end of a drill bit sub.