How to Choose the Right DTH Drill Bit: A Complete Selection Guide

A practical field guide to matching DTH (Down-The-Hole) button bits to rock formation, hole size, depth and hammer — for drilling managers, procurement officers and exploration engineers.

In this guide:

1. Why bit selection decides your cost per meter
2. Button shape: spherical vs ballistic vs conical
3. Bit face design: flat, convex, concave, drop-center
4. Matching diameter to hammer and application
5. Carbide grade and steel body
6. Flushing holes and shank compatibility
7. Rock-type decision table
8. Pre-order selection checklist
9. Frequently asked questions

Down-the-hole drilling has become the default method for deep, large-diameter and hard-rock holes — water wells, geothermal loops, production blast holes, foundation piles and mineral exploration. But the hammer is only half the story. The DTH drill bit is the component that actually contacts the rock, and the wrong choice quietly drains your budget through slow penetration, broken buttons and premature bit changes.

This guide distills two decades of bit manufacturing and field service into a selection framework you can apply before the next job. It pairs with our high-air-pressure DTH bit range and our full line of DTH drilling rigs.

1. Why bit selection decides your cost per meter

A DTH bit's performance is governed by four interacting variables: the button geometry, the face profile, the diameter and shank, and the carbide grade. Each must be matched to the dominant rock condition. Mismatches produce predictable failures:

• Sharp conical buttons in granite → tip breakage and short life.
• All-spherical buttons in soft clay → slow penetration and low efficiency.
• Low-toughness carbide at high air pressure → frequent button loss and cracking.
• Oversized bit → higher air consumption and drilling resistance; undersized bit → fails to reach required hole diameter.

The right bit is rarely the most expensive one — it is the one correctly matched to formation, hammer, compressor capacity and application. That is what keeps your cost per drilled meter low.

2. Button shape: spherical vs ballistic vs conical

Tungsten-carbide buttons are the wear-sensitive cutting elements of a DTH bit. Their shape controls the trade-off between penetration speed and wear resistance.

Gauge vs face buttons. Gauge buttons sit on the outer ring and grind against the borehole wall, so they wear fastest and must protect hole diameter. They are typically spherical and one hardness grade tougher than the face buttons. Face buttons break virgin rock and can use a slightly softer, faster-cutting grade. A XDDRILL high-air-pressure bit commonly pairs spherical gauge buttons with ballistic front buttons to balance life and speed.

3. Bit face design: flat, convex, concave, drop-center

The face profile changes how impact energy is distributed and how cuttings are evacuated.

Rule of thumb: concave for soft-rock speed, flat for versatility, convex for hard-rock durability, drop-center for straightness in broken ground.

4. Matching diameter to hammer and application

The bit diameter must match both the required hole size and the DTH hammer's shank and recommended range. Typical bands:

Our high-air-pressure bit line spans DHD3.5/DHD3.5A (90–108 mm, flat face), DHD340/DHD340A (108–130 mm, convex face) and DHD350/DHD350A (140–178 mm, convex/flat/concave faces) — covering water well, quarry, mining and geotechnical ranges in a single sourcing plan. See also our open-pit mining solution and slope reinforcement solution for matched rig-and-bit setups.

5. Carbide grade and steel body

Carbide grade determines hardness, toughness and wear resistance. It is matched to rock hardness, abrasiveness and operating pressure.

The bit body should be premium alloy steel with high toughness, fatigue resistance and proper heat treatment. Cold-press or interference-fit button retention (versus conventional brazing) reduces button fallout under heat and impact — a key reliability factor on deep, high-pressure jobs.

6. Flushing holes and shank compatibility

Flushing holes carry compressed air to the hole bottom, evacuating cuttings, cooling the bit and preventing regrinding. An optimized flushing design raises penetration, lowers temperature, reduces button wear and cuts jamming risk. Number, size and position should suit the rock, diameter, pressure and depth — wet or deep holes need enhanced flushing.

Shank compatibility. DTH bits connect via a splined shank, not threads. A QL60 hammer needs a QL60-shank bit; an SD8 hammer needs an SD8-shank bit. Always confirm the shank series (DHD, COP, QL, Mission, SD, NUMA) and diameter with your supplier before ordering. If your hammer is underperforming rather than your bit, see our guides on troubleshooting low impact energy and DTH hammer lubrication.

7. Rock-type decision table

8. Pre-order selection checklist

1. Formation: hardness (UCS/MPa), abrasiveness, fracturing, moisture.
2. Target hole diameter: within the hammer's recommended range.
3. Hammer shank series: DHD / COP / QL / Mission / SD / NUMA.
4. Button shape: matched to rock hardness and abrasion.
5. Face design: matched to formation and objective (speed vs life vs straightness).
6. Carbide grade: matched to impact and pressure.
7. Flushing: adequate holes for depth and wet conditions.
8. Body material: premium alloy steel, interference-fit buttons.
9. Depth: deeper holes demand higher wear resistance and stability.
10. Air supply: confirm compressor capacity supports the bit and hammer.

Need a matched DTH bit and rig for your project?

XDDRILL (Hubei Xingda) manufactures high-air-pressure DTH bits in DHD, COP, QL, Mission, SD and NUMA shank series from 90 mm to 178 mm+, backed by 20+ years of manufacturing, ISO9001 and CE certification, and field service in 50+ countries. Send your formation, hole diameter, depth and air capacity to sales@xingdamachinery.com for a tailored bit-and-rig recommendation, or visit our contact page.

Frequently Asked Questions

What is the difference between spherical, ballistic and conical DTH bit buttons?

Spherical buttons are rounded and most wear-resistant, preferred for hard, abrasive rock (granite, basalt, quartzite). Ballistic/parabolic buttons are sharp and penetrate fastest in soft to medium formations but wear quicker in abrasive ground. Conical buttons balance penetration and durability for medium-hard rock. Gauge buttons usually use spherical inserts for diameter protection.

Which DTH bit face design should I use?

Flat face distributes impact evenly and is the most durable for hard, abrasive rock and easy to resharpen. Convex/dome face protects gauge buttons and extends life in hard formations. Concave face concentrates energy at the center for fast penetration in soft to medium rock. Drop-center improves hole straightness in hard, fractured ground.

How do I match DTH bit diameter to the hammer?

The bit shank must match the hammer series (DHD, COP, QL, Mission, SD, NUMA) and the bit diameter should fall within the hammer's recommended drilling range. Common ranges: 90–110 mm for water well, anchoring and small construction; 110–140 mm for quarrying and general mining; 140–165 mm for production blast holes; 165–203 mm for large mining; 203 mm+ for deep water wells, geothermal and foundation work.

What carbide grade should a DTH bit use?

Carbide grade is matched to rock hardness and impact. High-cobalt fine-grain grades such as YG15C/K30 suit hard rock and high air pressure (≥1.2 MPa) with strong impact resistance. YG11C/K40 balances wear and toughness for abrasive sandstone. YG8C is a general-purpose medium-hard grade. YG6C offers high toughness for soft, weathered formations and rapid drilling.

Why are flushing holes important on a DTH bit?

Flushing holes let compressed air evacuate rock cuttings, cool the bit and prevent regrinding debris at the hole bottom. Optimized flushing improves penetration rate, lowers operating temperature, reduces button wear, keeps the hole clean and lowers the risk of bit jamming. Number, size and position should suit rock type, diameter, air pressure and depth.

Can I use one DTH bit for all rock types?

No. A single bit cannot perform optimally across all formations. Spherical buttons and flat/convex faces suit hard abrasive rock, while ballistic buttons and concave faces suit soft to medium ground. Mismatched bits cause button breakage, rapid wear or slow penetration. Match the bit to the dominant formation and keep a backup configuration for variable ground.

How do I confirm shank compatibility with my DTH hammer?

DTH bits connect via a splined shank, not threads. A QL60 hammer requires a QL60-shank bit; an SD8 hammer requires an SD8-shank bit. Provide your hammer model and target hole diameter to the supplier to confirm the correct shank series and bit size before ordering.

Where can I get DTH bits and drilling rigs matched to my project?

XDDRILL (Hubei Xingda) manufactures high-air-pressure DTH bits in DHD, COP, QL, Mission, SD and NUMA shank series from 90 mm to 178 mm+, plus pneumatic and full-hydraulic DTH drilling rigs. Share your formation, hole diameter, depth and air capacity with sales@xingdamachinery.com for a matched bit-and-rig recommendation.

Published by XDDRILL (Hubei Xingda) — pneumatic DTH and full-hydraulic core drilling rig manufacturer. Explore our full product range or read more industry news.