In a diamond bit having mud channels formed in the face thereof, a single row of diamonds is arranged along each mud channel. The diamonds are positioned so that the scraping edge of each diamond is between two perpendicularly arranged planes of the diamond and so that one of these planes lies in the wall of the mud channel.

An improved rotating diamond bit for earth boring is devised by incorporating generally triangular, prismatically shaped synthetic polycrystalline diamond elements in the teeth of the boring bit. The polycrystalline diamond elements are set on lands defined on the bit face such that two opposing triangular faces of the prismatic diamond element form a dihedral angle in the direction of travel of the element defined by the bit rotation. The polycrystalline diamond element is thus inclined with respect to the direction of linear travel of the element when the bit rotates. In other words, the normal to the parallel opposing triangular faces of the diamond element is acutely inclined with respect to the direction of travel of the element. A shoulder-to-gage transition pattern of the junk slot, waterway and collector is arranged to uniformly distribute the flow of fluid across the shoulder to guage transition. Further, the distribution of fluid from the central conduit within the longitudinal core of the bit to a plurality of nozzles which merge with corresponding waterways on the bit face is arranged such that fluid is preferentially delivered to a radially innermost nozzle and thereafter in a graduated series of steps in lesser amounts to a series of sequenced nozzles more radially disposed from the center of the rotating bit.

A rotary drag bit is disclosed which eliminates the problem of the disorientation and dislodging of cutting elements on the bit body. The drag bit includes a replaceable head cover which is adapted to be removably attached to the face and gage surfaces of the bit body head portion. The head cover is preferably made of tungsten carbide and includes a plurality of projections integrally formed thereon. These projections function as a backing and include a planar surface for receiving a plurality of synthetic diamond discs which are bonded thereto. The projections and discs are oriented radially on the bit body to face the direction of drag bit travel. The discs form cutting edges for gouging and removing cuttings from the bottom of the borehole. The tungsten carbide head cover functions as a wear surface around the bases of the cutting elements to prevent erosion thereof. By being integrally formed with the head cover, the projections are prevented from rotating or becoming dislodged. By being removable the head cover can be replaced when worn and the bit body can be used over again.

A steel tooth, particularly suited for use in a rolling cone bit, includes a root region, a cutting tip spaced from the root region and a gage facing surface therebetween. The gage facing surface includes a knee, and is configured such that the cutting tip is maintained at a position off the gage curve. So positioned, the cutting tip is freed from having to perform any substantial cutting duty in the corner on the borehole corner, and instead may be configured and optimized for bottom hole cutting duty. The knee on the gage facing surface is configured and positioned so as to serve primarily to cut the borehole wall. It is preferred that the knee be positioned off gage, but that it be closer to the gage curve than the cutting tip.

A long lasting rotary drill bit for drilling a hole into variable hardness geological formations that has a self-actuating mechanism responsive to the hardness of the geological formation to minimize the time necessary to drill a borehole. A long lasting rotary drill bit for drilling a hole into variable hardness geological formations that has a mechanism controllable from the surface of the earth to change the mechanical configuration of the bit to minimize the time necessary to drill a borehole. A monolithic long lasting rotary drill bit for drilling a hole into a geological formation having hardened rods composed of hard material such as tungsten carbide that are cast into a relatively soft steel matrix material to make a rotary drill bit that compensates for wear on the bottom of the drill bit and that also compensates for lateral wear of the drill bit using passive, self-actuating mechanisms, triggered by bit wear to drill relatively constant diameter holes.