DETAILED DESCRIPTION OF THE INVENTION The numeral 11 in the drawing designates a typical earth boring drill bit having a threaded shank 13 for attachment to a drill string member.
Nozzles 15 are provided as a means for directing a flow of fluid toward the borehole bottom.
The bit shown in FIG.
1 is also provided with three depending legs or head sections 17 that each support a toothed, rotatable cutter 19, sometimes referred to as a "cone.
" FIG.
2 shows a cutter 19 from the side, including a conical gage surface 21 extending from the backface 23, to the heel row teeth 25.
The gage surface is formed with alternate areas of steel ribs 27 and bands 29 of composite hardfacing material consisting essentially of an alloy steel matrix and particles of sintered or cemented tungsten carbide.
This particular cutter has an intermediate row 31 of teeth and a extreme inner row or spear point 33.
The cutter is mounted on leg 17 by means of a cantilevered shaft that forms a bearing means on the interior of the cutter.
As shown in FIG.
2, each of the teeth has a tooth crest 37 defined between opposing flanks 39,41.
In operation, the bit is rotated so that the cone or cutter 19 revolves clockwise about an imaginary axis passing vertically through the apex of the spear point 33, as viewed in FIG.
2.
Thus, each of the teeth contact the formation being drilled so that on the heel row 25 and intermediate row 31 the respective flanks 43, 45 are trailing while flanks 47, 49 are leading.
In the cone illustrated in FIG.
2, each tooth of the heel row 25 is hardfaced on the leading flank 47 with a first, coarse tube hardfacing while each trailing flank 43 is hardfaced with a second, finer tube hardfacing.
The intermediate row is similarly hardfaced.
The choice of flank to be hardfaced is a matter of experience and varies from one formation to another and also varies with the expected drilling conditions such as weight, rotary speed, type and rate of circulation of drilling fluids, etc.
In some formations and under some conditions, the hardfacing to be used may be the reverse of that illustrated, or other surfaces of the tooth may be hardfaced as well
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Metal Working 
