Rotary-percussion drill bit with antiwedging gage structure

Claim 1

IN A ROTARY-PERCUSSION BIT OF THE TYPE USING WEAR RESISTANT INSERTS FOR CUTTING STRUCTURE, SUCH INSERTS HAVING BASES AT ONE END AND CUTTING TIPS OPPOSED THERETO, SUCH BIT HAVING A UPPER STEEL SHANK ADAPTD FOR CONNECTION TO A PERCUSSION TOOL AND A LOWER STEEL BODY TERMINATING IN A BLUNT BOTTOM SURFACE AND HAVING A CIRCUMFERENTIAL GAGE SURFACE INTERSECTING SAID BOTTOM SURFACE, SUCH INSERTS BEING DISPOSED WITH THEIR BASES SECURED IN SAID BODY AND THEIR CUTTING TIPS PROTRUDING FROM THE BOTTOM SURFACE OF SAID BODY AND DISTRIBUTED IN CONCENTRIC ROWS IN SPACED APART RELATION, THE INSERTS OF THE OUTERMOST OR HEEL ROW BEING ANGULARLY DISPOSED WITH THEIR CUTTING TIPS PROTRUDING AT SAID INTERSECTION AND THEIR BASES SECURED IN THE BODY ABOVE SAID RADIALLY INWARDLY FROM THEIR CUTTING TIPS WHILE THE INSERTS OF THE INNER ROWS ARE DISPOSED WITH THEIR BASES GENERALLY DIRECTLY ABOVE THEIR CUTTING TIPS, THE IMPROVEMENT COMPRISING SAID CIRCUMFERENTIAL GAGE SURFACE HAVING A NET AREA LESS THAN THE PRODUCT OF THE NUMBER OF HEEL INSERTS, THE AVERAGE CROSS SECTIONAL DIMENSION OF SUCH HEEL INSERTS, AND THE BIT DIAMETER.