How to Select DTH Equipment and Tool? Depth and Diameter Are Key
Mar 14,2026
In DTH (Down-The-Hole) drilling, the depth and diameter of the borehole are the core basis for equipment selection. The depth determines the required air pressure rating of the hammer and the performance of the air compressor; the diameter determines the size of the hammer and bit. These three components must be precisely matched to achieve efficient drilling and cost control. Incorrect selection leads to low efficiency, high wear, or even project failure. This article details the matching principles.
Core Equipment Matching Guide Based on Borehole Parameters
The following table clearly illustrates how to match the key selection parameters for the Hammer, Bit, and Air Compressor based on different ranges of borehole diameter and depth.
Borehole Diameter (mm) | Recommended DTH Hammer | Recommended Bit Diameter (mm) | Min. Air Pressure (bar) | Suitable Depth Range (m) | Typical ROP (m/h) |
|---|---|---|---|---|---|
90–110 | DHD3.5 / QL3.5 | 95–105 | 7–10 | 0–200 | 15–25 |
110–130 | DHD4 / QL4 | 115–125 | 10–14 | 0–300 | 12–22 |
130–152 | DHD5 / QL5 | 140–152 | 12–17 | 0–400 | 10–20 |
152–165 | DHD6 / QL6 | 152–165 | 15–20 | 0–500 | 8–18 |
200–254 | HD50 / SF6 | 200–254 | 17–24 | 0–600 | 6–15 |
254–311 | HD65 / SF8 | 254–311 | 20–28 | 0–800 | 5–12 |
The Golden Rules for DTH System Matching and Summary
In summary, matching a DTH drilling system follows three golden rules:
- The Hammer is the Heart: Borehole diameter determines its size, while depth and rock hardness determine its pressure rating—"Deep holes, hard rock, large diameter" always require a high-pressure hammer.
- The Bit is the Executor: Its size must strictly match the hammer. "Prioritize efficiency with blast-hole bits for soft rock; prioritize longevity with button bits for hard rock." For deep holes in hard rock, premium button bits are non-negotiable.
- The Air Compressor is the Power Source: "Pressure ensures impact, CFM ensures cleanup." Insufficient pressure fails to break rock, while insufficient CFM leads to rod sticking or hole blockage. CFM must be precisely calculated based on annular area with a safety margin.
Proper matching is the foundation for achieving efficient, economical, and safe drilling. Neglecting the decisive influence of depth and diameter on equipment selection will prevent even advanced machinery from performing to its potential.
Have you ever encountered construction challenges in your projects due to improper DTH equipment selection? Which parameter in equipment compatibility do you value the most? Share your hands-on experiences and insights in Our Community Forum.
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