BQ NQ HQ PQ Boart Longyear Surface Set Diamond Core Bits For Faster Drilling Stone Surface-Set Diamond Bits are set with a singular layer of natural or synthetic diamond utilizing a hard matrix compound on the face of the bit. The diamond set design ensures sufficient overlap to prevent premature wear of the matrix. Surface-Set diamond bits are primarily recommended for use in drilling relatively soft, abrasive, unconsolidated formations that are not effectively drilled by