Secondary cutting structure

A rolling cone cutter for a three cone roller bit comprising:

• a generally conical roller cutter body having an external surface;
• a recessed groove within the roller cutter body, the groove having a bottom surface;
• a plurality of primary cutting elements retained in a land on the roller cutter body and projecting outwardly from the external surface of the land;
• and
• a plurality of secondary cutting elements retained within the bottom surface of the groove of the roller cutter body, said secondary elements not projecting past the elevation of the land.

A method of drilling a borehole comprising:

• disposing into a borehole a drill bit having a rolling cutter comprising:
• 1) a rolling cutter body;
• 2) a plurality of primary cutting elements that are retained within and extend outwardly from lands on the rolling cutter body;
• and
• 3) a plurality of secondary cutting elements that are retained within grooves on the rolling cutter body and do not extend outwardly past the lands when the cutter body is unworn;
• engaging portions of a borehole with the primary cutting elements but not with the secondary cutting elements so as to cut borehole;
• wearing the primary cutting elements and cutter body so that the primary cutting elements become substantially ineffective to cut borehole;
• and
• engaging portions of a borehole with the secondary cutting elements to continue to cut borehole.