Drill bit

Claim 1

A DRILL BIT COMPRISING A BIT BODY HAVING A LONGITUDINAL AXIS EXTENDING BETWEEN OPPOSITE ENDS OF THE BODY, ONE END OF THE BODY HAVING A PAIR OF GROOVES, EACH GROOVE DISPOSED ON OPPOSITE SIDES OF SAID AXIS, EACH GROOVE HAVING A CONCAVE BOTTOM SURFACE EXTENDING OUTWARDLY RELATIVE TO THE AXIS AND SLOPING TOWARD THE OTHER END OF THE BODY, AN INNER NON-WORK ENGAGING LAYER FORMED OF CARBIDE MATERIAL IN EACH GROOVE AND INTEGRALLY BONDED TO THE CONCAVE SURFACE IN THE GROOVE, THE SIDES OF EACH INNER LAYER SPACED FROM THE SIDES OF ITS RESPECTIVE GROOVE, THE OUTER END OF EACH INNER LAYER SPACED FROM THE OUTER END OF ITS RESPECTIVE GROOVE, EACH INNER LAYER HAVING A CONVEX OUTER SURFACE SPACED FROM SAID CONCAVE BOTTOM SURFACE, AN OUTER EXPOSED LAYER OF CARBIDE MATERIAL IN EACH GROOVE OCCUPYING THE REMAINDER OF THE SPACE THEREIN NOT OCCUPIED BY THE INNER LAYER AND INTEGRALLY BONDED TO THE SURFACES OF SAID GROOVE AND INNER LAYER WHEREBY EACH OUTER LAYER COMPLETELY ENCLOSES ONE OF SAID INNER LAYERS, EACH OUTER LAYER HAVING A PORTION PROJECTING OUT OF ITS RESPECTIVE GROOVE AND FORMED WITH A CUTTING EDGE NORMAL TO SAID AXIS, THE OUTER LAYERS OF CARBIDE MATERIAL CHARACTERIZED BY BEING HARD AND HAVING PREDOMINANTLY WEAR RESISTANT PROPERTIES, EACH INNER LAYER OF CARBIDE MATERIAL BEING OF SUBSTANTIAL HARDNESS BUT LESS HARD THAN THE OUTER LAYERS AND HAVING MORE RESILIENCY AND TOUGHNESS, A BINDER MATERIAL INTEGRALLY UNITING SAID LAYERS AND SAID BODY.