Equipment Assembly and Positioning
Just as building with blocks requires the right baseplate, DTH (Down-The-Hole) drilling begins with precise positioning:
Chassis leveling: Calibrate the rig using a level; an inclination exceeding 3° will affect drilling verticality.
Drill rod connection: Apply specialized grease to the threads; hand-tighten first, then secure with a wrench by an additional half-turn.
Air compressor connection: Check air hose seals; air leakage must be less than 5% at 0.7 MPa pressure.
Hole Collaring and Stabilization Techniques
This stage determines the success of the drilling operation:
Low-speed collaring: Maintain an initial rotation speed of 30 rpm; gradually increase speed after the bit penetrates 10 cm into the rock.
Air pressure control: Maintain a cuttings-clearing airflow of 15 m³/min; accumulated rock dust accelerates bit wear.
Angle correction: Stop and check every 50 cm of drilling; make timely adjustments if the deviation exceeds 2°.
Continuous Drilling and Completion
Maintaining a steady rhythm is more important than using brute force:
Parameter matching: For medium-hard rock, a combination of 0.8 MPa air pressure and 80 rpm rotation speed is recommended.
Drill rod management: Perform reverse rotation to clear cuttings after adding every three drill rods to prevent the drill from getting stuck.
Hole completion: Decelerate 0.5 m before the target depth; stopping abruptly may cause the bit to jam.
