the shale the leading side is configured so that the flow vectors of the shale and mud do not make sharp turns as they pass the tooth generally that means that there will be little if any portion of the leading side that is flat and normal to the direction of rotation of the cutter preferably all surfaces having any significant width on the leading side are at least 45 u00b0 from a position facing into the direction of rotation in the embodiment of fig2 and 3 heel row tooth 29 is generally conical except for the flat outer end 35 rather than being elongated the crest or apex 36 is rounded and dome shaped the leading and trailing flanks and the inner end referenced as inner portion 37 are rounded into the shape of a cone inner portion 37 forms a heel row tooth 29 that is thus partially conical in shape the width or diameter of apex 36 is measured at the point of curvature from the sloping sides the width or diameter of the base of tooth 29 is measured at the point where tooth 29 joins the supporting metal of cone 21 and it is measured from outer end 35 to the inner portion 37 the width of apex 36 is preferably less than one third the width of the base the underlying support metal or tooth stub 31 is formed in this partially conical shape hardfacing 33 is applied over tooth stub 31 typically in a generally uniform thickness the leading side of conical inner portion 37 has no flat areas that might impede the flow of viscous shale and drilling mud referring again to fig1 a plurality of inner row.