The invention is embodied in a heavy duty drill bit for hard/soft rock drilling comprising a high fatigue-resistant, high alloy steel bit body having a PCD cutter member and an enlarged shank portion constructed to accommodate torsional forces at high thrust pressures, and reamer means for compensating the effect of bore hole rifling. The invention further involves the method of forming a roof bolting matrix in extremely hard rock formations having a compression strength up to about 50,000 psi using PCD wafers on a high tensile strength steel body coupled by a heavy duty shank through high fatigue-resistant reamer means to a high strength drive steel member.