The hot-pressed diamond drill bit has high hardness abrasion resistance and toughness. 1.size OD 56mm,59mm,75mm,91mm,110mm,130mm,150mm,168mm,200mm,219mmare generally available for stock, other standard sizes are also ordered.2.wooden cases can be used as required.3. Hot-pressed Diamond Drill Bit Hardness and Rock Drillability Grades FormRock Drillability GradeBit Hardness (HRC)Rock ...