Rotary drill bit with improved cutter and seal protection

A rotary cone drill bit for forming a borehole, said drill bit comprising:

• a body with an underside and an upper end portion adapted for connection to a drill string for rotation about a central axis of said body;
• a number of angularly-spaced arms integrally formed with said body and depending therefrom, each of said arms having an inside surface with a spindle connected thereto and an outer shirttail surface, said spindle projecting generally downwardly with respect to said body and inwardly with respect to said axis and having a generally cylindrical upper end portion connected to said inside surface and an inner sealing surface on said spindle within said upper end portion;
• and
• a plurality of cone cutters equalling said number of arms and mounted respectively on one of said spindles, each of said cone cutters including an internal generally cylindrical wall defining a cavity for respectively receiving said spindle such that a generally cylindrical gap is formed between said spindle and cavity wall, said gap extending throughout its length in a direction substantially parallel to a central axis of said spindle and having an outer segment intersecting with said shirttail surface and opening upwardly with respect to said body and outwardly from said shirttail surface, including an outer sealing surface in said cavity wall concentric with said inner sealing surface, and including a seal element sealing between said inner and outer sealing surfaces;
• each of said cutters including a generally conical composite cutter body having a base formed of a conventional steel material with a backface formed of a hard metal material disposed on an outer portion of said base and having a tip formed of a conventional steel material, wherein said hard metal material is incompatible with heat-treating processes for said tip;
• and
• wherein for each of said cutters said base is generally ring-shaped and formed separately of said tip.