drill the rock hole within diameter of 50mm. The drill tools are used in metallurgy mine, geological exploration, water
conservancy construction, electricity, traffic, tunnel, quarry, national defence stone project etc. 8 Top Hammer Rock Drilling Bits H22 7 Degree Taper Bit Drill Mining Rock Tapered Copper Drill Bits for Construction Works Top Hammer Rock Drilling Bits H22 7 Degree Taper Bit Drill Mining Rock Tapered Copper Drill Bits for Construction Works