As a technical expert in the field of hardware manufacturing, this article analyzes the design, classification, and suitable application scenarios of down-the-hole (DTH) drill bits.
Structural Design and Performance Advantages
1. Carbide Insert Configuration
Spherical Inserts: Featuring spherical tips, these are suitable for crushing hard rock (e.g., granite, basalt), with a single-insert compressive strength exceeding 2000 MPa.
Chisel Inserts: Featuring a saw-toothed design, these are adapted for medium-hard rock strata (e.g., limestone, sandstone), reducing energy consumption per unit of drilling footage.
2. Standardized Thread Connections
Mainstream thread specifications include T38 (for small-scale drilling rigs) and T45 (for deep-hole mining operations), with a thread tolerance of ±0.01 mm.
3. Optimized Flushing Channels
Large-diameter drill bits employ a spiral air channel design; when paired with a compressed air velocity of ≥25 m/s, this enhances chip removal efficiency by 40%.
Application Scenario Classification and Selection Logic
1. Classification by Industry
Mining: Spherical inserts are recommended for metal mines (insert pitch < 15 mm), while chisel inserts are recommended for coal mines (insert height 8–10 mm).
Construction Engineering: Medium-diameter drill bits (100–300 mm) are recommended for pile foundation construction, with a hole diameter tolerance of ≤2‰.
Water Well Drilling: Composite geological formations require a stepped-row insert configuration to balance both efficiency and cost-effectiveness.
2. Adaptation to Air Pressure Systems
Low Air Pressure Bits (0.7–1.2 MPa): Suitable for soft rock strata, with a single-hole depth of ≤15 m.
High Air Pressure Bits (2.5–3.5 MPa): Adapted for deep-hole blasting in metal mines, delivering an impact energy of ≥450 J per blow.
Key Aspects of Operation & Maintenance and Strategies for Extending Service Life
1. Wear Monitoring Techniques
Carbide Insert Wear Thresholds: Inserts must be replaced if wear on the tip height exceeds 3 mm; drilling must be halted for regrinding if thermal cracks on the cutting edge exceed 0.5 mm.
Spline Groove Inspection: Circumferential wear exceeding 1.5 mm will result in torque transmission failure; if the mating clearance exceeds 0.3 mm, repair is required. 2. Lubrication and Rust Prevention Strategy
Molybdenum disulfide lubricant should be applied to the threaded connections; for long-term storage, NC200 series rust-preventive oil must be applied.
3. Domestic Technological Breakthroughs
A single PDC down-the-hole (DTH) drill bit achieved a total footage of 2,627 meters. Its efficiency in flint formations reached three times that of conventional bits, while its impact toughness was enhanced by 60%.
In the future, DTH drill bits will evolve toward high-strength, lightweight designs. It is recommended to establish a wear-and-tear database to optimize replacement cycles. By precisely matching rock formation characteristics with operating parameters, an optimal balance between efficiency and cost can be achieved.