Patent ID: 7458646

Claim:
An elongate rotatable cutting tool body with a central longitudinal axis, the tool body comprising: an axial forward end and an axial rearward end; a head portion, a shank portion and a collar portion, and the collar portion being mediate of and contiguous with the head portion and the shank portion; the head portion being adjacent to the axial forward end, and the shank portion being adjacent to the axial rearward end; the cutting tool body being made of steel having a nominal composition comprising 0.33-0.38 weight percent carbon, a minimum of 0.0005 weight percent boron, 1.10-1.35 weight percent manganese, 0.15-0.30 weight percent silicon, a maximum of 0.045 weight percent sulfur, a maximum of 0.035 weight percent phosphorus, and balance of iron; an axial forward hardness region beginning at and extending a first pre-selected distance in an axial rearward direction from the axial forward end to encompass the entire head portion and at least an axial forward section of the collar portion, the axial forward hardness region having a hardness equal to or greater than a first hardness wherein the first hardness is equal to 52 Rockwell C, and the axial forward hardness region having a first average hardness wherein the first average hardness is greater than 52 Rockwell C; an axial rearward hardness region beginning at and extending a second pre-selected distance in an axial forward direction from the axial rearward end to encompass an axial rearward section of the shank portion, and the axial rearward hardness region having a third average hardness; a transition hardness region mediate of and contiguous with the axial forward hardness region and the axial rearward hardness region, the transition hardness region encompasses an axial rearward section of the collar portion and an axial forward section of the shank portion, and the transition hardness region having a second average hardness; and the second average hardness being less than the first hardness, and the third average hardness being less than the second average hardness.