Top Hammer Drill Rod Introduction The Top Hammer Drill Rod is a high-precision threaded rock drilling component engineered for drifting, tunneling and underground mining applications in complex rock and rough terrain conditions. Available in a full range of thread types from R22 to GT60 and diameters from Hex25 to RD60, these drill rods are manufactured from high-strength alloy steel imported from reputable steel mills, with CNC milling and proprietary heat treatment