in steerable applications requiring greater durability at the shoulder 236 large chamfer cutters 110 may optionally be employed but oriented at a 10 u00b0 cutter backrake further the chamfer angle of cutters 110 in each of regions 226 and 236 may be other than 45 u00b0 for example 70 u00b0 chamfer angles may be employed with chamfer widths looking vertically at the cutting face of the cutter in the range of about 0 035 to 0 045 inch cutters 110 being disposed at appropriate backrakes to achieve the desired chamfer rake angles in the respective regions a boundary region rather than a sharp boundary may exist between first and second regions 226 and 228 for example rock zone 46 bridging the adjacent edges of rock zones 42 and 42 of formation 40 may comprise an area wherein demands on cutters and the strength of the formation are always in transition due to bit dynamics alternatively the rock zone 46 may initiate the presence of a third region on the bit profile wherein a third size of cutter chamfer is desirable in any case the annular area of profile 224 opposing zone 46 may be populated with cutters of both types i e width and chamfer angle and employing backrakes respectively employed in region 226 and those of region.