Diamond cutter rock bit with penetration limiting

A rotary rock bit comprising:

• a bit body;
• a plurality of diamond cutters on the bit body each with a cutting edge extending from the bit body a selected distance for engaging the bottom of a hole being drilled at a selected rake angle and shearing rock during drilling;
• and
• means on the rock bit for engaging the rock being drilled and limiting depth of penetration of the diamond cutters into rock during drilling to a depth of more than about one-fourth and less than about three fourths of the length of the diamond cutters extending from the body.

A rotary rock bit comprising:

• a bit body;
• a plurality of diamond cutters each having a cutting edge;
• means for mounting the diamond cutters on the bit body with the cutting edge protruding from the bit body at a selected rake angle for shearing rock upon rotation of the rock bit;
• and
• means mounted on the bit body for engaging rock being drilled and limiting depth of penetration of the diamond cutters into rock being cut to less than about three-fourths of the extent of protrusion of the cutting edge of the diamond cutter from the bit body.

A rotary rock bit comprising:

• a bit body;
• means at the upper end of the bit body for connecting the rock bit to a drill string;
• a first plurality of arms extending downwardly from the bit body;
• a plurality of diamond cutters mounted on the first plurality of arms for engaging rock being drilled at a selected rake angle and drilling a portion of the bottom of a hole;
• a second plurality of legs extending downwardly from the bit body and interspersed between the first plurality of arms;
• and
• a rolling cone cutter mounted on each of the second plurality of legs, each rolling cone cutter comprising a plurality of carbide inserts protruding from the surface of the cutter cone a distance less than the protrusion of the diamond cutters from the arms for limiting penetration of the diamond cutters into rock being drilled to less than the protrusion of the diamond cutters from the arms.

A core bit comprising:

• a bit body having an axial core receiving passage therethrough;
• a plurality of diamond cutters mounted on the bit body around the passage for drilling an inner annulus of rock around a core, at least one of the diamond cutters having an edge for defining the gage of the core, each diamond cutter comprising a diamond plate bonded to a slug inserted in the bit body so that the diamond plate engages the rock at a selected rake angle;
• and
• a plurality of rolling cone cutters mounted on the bit body for drilling an outer annulus of rock around the inner annulus, each rolling cone cutter including a plurality of carbide inserts protruding from the surface of the respective cone a distance less than the length of the diamond plates for limiting depth of penetration of the diamond cutters to less than the length of the diamond plates.

A rotary rock bit comprising:

• a bit body;
• a plurality of diamond cutters mounted on the bit body for drilling a plurality of annular grooves in the bottom of a hole;
• a plurality of rolling cone cutters mounted on the bit body for drilling at least a portion of the bottom of the hole, the portion drilled by the rolling cone cutters at least partly overlapping the portion drilled by the diamond cutters;
• and
• a plurality of carbide inserts protruding from the surface of each rolling cone cutter, the carbide inserts being in rows on the rolling cone cutters that drill annular grooves the same as at least a portion of the grooves drilled by the diamond cutters, and wherein the carbide inserts protrude from the surface of the rolling cone cutters a distance less than the protrusion of the diamond cutters from the bit body for limiting depth of penetration of the diamond cutters into the bottom of the hole to less than the length of protrusion of the diamond cutters from the bit body.