Top hammer drilling threaded button bits (commonly just called button bits) come in a wide variety of types, with no single fixed number — manufacturers like Sandvik, Epiroc (formerly Atlas Copco), RockHound, and others offer dozens of configurations. The exact count depends on how you classify them, but they are typically grouped by 4 main categories:
- Thread Type (connection to drill rod) — This is the most common way to categorize them, as it determines compatibility with specific rock drills and rigs.
- Face Design (bit front shape) — Affects penetration, flushing, and straightness.
- Button Shape (carbide insert profile) — Influences speed vs. wear resistance.
- Skirt/Body Design (e.g., regular vs. retrac) — For stability and retrieval.
1.By Thread Type (The Most Common Way to Categorize)
Thread type determines compatibility with your drill rods and rig. Most manufacturers offer 10-15 major thread types for top hammer bits, with sizes ranging from 28mm to 152mm in diameter. Popular threads include R-series (rope threads) for smaller holes and T-series (trapezoidal) for larger, heavier-duty applications.
Here’s a breakdown in a handy table:
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| Thread Type | Typical Diameter Range | Best For |
|---|---|---|
| R25 | 28-45 mm | Small holes, bolting, tunneling |
| R28 | 32-51 mm | Drifting, medium holes |
| R32 | 38-64 mm | Bench drilling, general mining |
| R35 | 45-76 mm | Medium bench, longhole drilling |
| SR28 / SR35 | 32-64 mm | Specialized small-medium holes with enhanced energy transfer |
| R38 | 51-89 mm | Production drilling |
| T38 | 64-102 mm | Bench and tunneling |
| T45 | 76-127 mm | Heavy quarrying, large-scale blasting |
| T51 | 89-152 mm | Large production holes |
| ST58 / ST68 | 102-152 mm+ | Deep longhole drilling |
| GT60 | 102-152 mm+ | High-performance mining & tunneling |
2.By Face Design (Affects Penetration and Hole Straightness)
The face (front) shape influences how the bit interacts with rock, flushing efficiency, and deviation control. There are 4-6 main face designs, chosen based on rock type and desired speed vs. accuracy.
- Drop Center (Concave): Recessed center for better centering and straighter holes. Great for medium-hard rock; improves flushing.
- Convex (Dome): Rounded for aggressive penetration in soft to medium rock. High speed but may wander in hard rock.
- Reaming Type: For enlarging holes; often dome-shaped.
- Cross or X Type: Less common for buttons, but used in specialized bits for fractured rock.
Table for Selection:
| Face Design | Rock Type Suitability | Advantages | Disadvantages |
|---|---|---|---|
| Drop Center (Concave) | Medium-Hard Rock | Excellent hole straightness, superior centering, good flushing efficiency | Moderate penetration rate compared to convex designs |
| Convex (Dome) | Soft to Medium Rock | Aggressive penetration, fastest ROP (rate of penetration), high drilling speed | Prone to hole deviation / wandering in harder or fractured formations |
| Reaming Type (often dome-shaped) | Hole enlargement in various rock types | Effective for reaming / oversize holes, maintains gauge stability | Not optimized for primary drilling, slower initial penetration |
| Cross / X Type | Fractured / Broken Rock | Better stability in unstable ground, reduces deviation in fractured zones | Less common in modern button bits, lower overall ROP in competent rock |
3.By Button Shape (Impacts Speed vs. Wear Resistance)
The carbide buttons’ profile is crucial for rock fracturing. There are 3-6 common shapes, with mixes (e.g., ballistic front + spherical gauge) for optimization.
- Spherical (Dome/Round): Best for hard, abrasive rock (F14+); high wear resistance but slower.
- Ballistic (Semi-Ballistic/Parabolic): Pointed for soft-medium rock (F12 or less); fast penetration but wears quicker.
- Conical (Sharp/Tapered): For very hard or soft rock; excellent fracturing but fragile.
Quick Comparison:
Standard Button Bits
Standard button rock drill bits are the most commonly used type of button rock drill bit. They are designed with carbide button on the tip and are suitable for drilling through hard rock formations. Standard button rock drill bits are available in a range of sizes and can be used for both surface and underground drilling.
Suitable: General rock drilling with balanced speed and durability.
Retrac Button Bits
Retrac button rock drill bits are designed with a retractable drill bit that can be extended and retracted as needed. This feature allows the drill bit to maintain a constant contact with the rock surface, resulting in a more efficient drilling process. Retrac button rock drill bits are ideal for drilling through loose rock formations and are commonly used in mining and tunneling operations.
| Feature | Specification |
|---|---|
| Design | Rear-facing reaming buttons – strategically placed for efficient back-reaming and hole enlargement |
| Rock Type Suitability | Fractured, blocky, loose, or collapsing formations – excels where borehole stability is poor |
| Primary Applications | Surface open-pit mining, tunneling, underground development, raise boring, and exploration drilling |
| Key Benefits | Improved hole enlargement in unstable ground, reduced risk of hole collapse, better alignment in fractured rock, faster reaming cycle |
Suitable: Drilling in unstable formations where hole collapse is a risk. RockHound’s retrac button bits are engineered with high-strength steel bodies and premium carbide inserts to resist breakage.
Drop Center Button Bits
Drop center button rock drill bits are designed with a slightly concave tip that creates a central depression on the rock surface. This feature allows the drill bit to maintain a more stable contact with the rock surface, resulting in a more efficient drilling process. Drop center button rock drill bits are suitable for drilling through hard rock formations and are commonly used in quarrying and mining operations. For efficient and safe mining and tunneling operations, selecting the right type of mining drill bits is crucial.
| Feature | Specification |
|---|---|
| Face Design | Concave with central drop |
| Rock Type | Hard, abrasive rock |
| Applications | Long-hole drilling, quarrying |
Suitable: Straight, deep holes in competent rock. Ideal for drilling a hole in a rock with precision in underground drill bit applications.
Ballistic Button Bits
Ballistic button rock drill bits are designed with multiple carbide buttons on the tip that provide a higher impact force and a faster drilling process. This type of carbide button bit is suitable for drilling through medium-hard rock formations and is commonly used in quarrying and mining operations.
Suitable: High-speed drilling with aggressive cutting. RockHound offers custom ballistic button bits for soft to medium rock with low-cost threaded button bit options
Spherical Button Bits
Spherical button rock drill bits are designed with many spherical carbide buttons on the tip that provides a high impact force and is highly resistant to wear and tear. This type of drill bit is suitable for drilling through hard and abrasive rock formations and is commonly used in mining and tunneling operations.
Suitable: Long-life drilling in extreme conditions. RockHound’s spherical drill bits use premium grade carbide for maximum button retention and bit life.
4.By Skirt & Body Design (For Stability and Retrieval)
The skirt (body) affects bit retrieval in fractured rock. 3-5 main designs:
- Standard/Normal Skirt: Straight body; for stable, solid rock.
- Retrac (Retractable): Tapered or splined for easy pull-back in loose/fractured rock; prevents jamming.
- Straightrac: Enhanced retrac for straight holes.
- Heavy Duty/Guide Skirt: Reinforced for abrasive conditions or guiding.
- Short/Long Skirt: Variations for specific depths.
From GSS(Guiyang Special Steel as our supplier), retrac is essential for underground drilling.
Specialized / Premium Types
Manufacturers offer optimized variants for extreme conditions:
- Autobit (Sandvik) — Extra-long grinding intervals for automation/longhole drilling.
- Powerbit (Epiroc) — High-performance with advanced button treatment.
- Top Center or Speedbit — Raised center buttons for faster collaring/straighter holes.
- Heavy Duty / High-Performance(RockHound) — Thicker body, larger buttons for quarrying/production.
Quick Selection: Main Categories & Use
| Category | Main Types / Sub-Types | Best For | Typical Benefit |
|---|---|---|---|
| Button Shape | Spherical, Ballistic, Conical / Parabolic | Hard/abrasive rock → Spherical Medium rock → Ballistic |
Wear resistance vs. penetration speed trade-off: Spherical offers longest life in highly abrasive conditions, Ballistic delivers faster ROP in medium-hard formations |
| Face Design | Drop Center, Convex | Fractured / broken rock → Drop Center Hard / competent rock → Convex |
Enhanced hole straightness, superior flushing efficiency, reduced deviation, and better overall stability in top hammer drilling |
| Skirt | Standard, Retrac | Unstable / collapsing ground → Retrac | Prevents bit jamming and hole collapse, improves reaming performance, reduces stuck bit risks in fractured or loose formations |
| Thread | R-series (small), T-series (medium), GT/ST (large) | Matched to bit diameter & hammer power requirements | Ensures perfect compatibility, maximum energy transfer efficiency, minimized thread wear and premature failure |
| Specialized | Autobit, Powerbit, Top Center, Speedbit | Automated drilling, longhole production, high-volume operations | Extended service life, significantly higher ROP, reduced bit changes and downtime → lowest cost per meter in high-production top hammer drilling |
Notice:There isn’t one single number of types — it’s modular! Most operations stock 4–8 common combinations (e.g., T45 ballistic drop center retrac, T38 spherical flat standard) and select based on rock type, hole depth, and rig. For your specific drilling (e.g., quarry vs. tunneling), matching the right combo can boost meters drilled per bit by 20–100%!
If you Contact Us your rock type or thread size, RockHound can narrow it down further.
How to Choose the Right Top Hammer Button Bit Type
Factors to consider:
- Rock Hardness: Use Mohs or Protodyakonov scale (e.g., spherical for hard granite).
- Hole Size/Depth: Smaller threads for shallow holes.
- Drilling Conditions: Retrac for fractured rock.
- Rig Compatibility: Match threads and optimize parameters (e.g., 50-150 RPM rotation).
| Factor | Recommendation |
|---|---|
| Rock Hardness | Soft to medium → Ballistic Hard & competent → Spherical Very hard & abrasive → Spherical + Retrac / Drop Center |
| Hole Depth | < 10 m → Standard skirt / Ballistic buttons > 10 m → Drop Center face / Retrac skirt |
| Flushing Conditions | Poor flushing / broken ground → Drop Center Good flushing / stable ground → Standard / Spherical |
| Drill Rig & Thread | Match thread to rig power & bit size: T38 (small/medium), T45 (medium), T51 (large/heavy duty) |
Conclusion: Optimize Your Drilling with the Right Button Bit
There isn’t a fixed “how many” for top hammer button bits, but understanding these 4 classifications empowers you to select the best for your project. Whether it’s an R32 flat face for hard rock or a T51 retrac for mining, the right choice boosts efficiency and cuts costs.
The classification of top hammer drill button bits is based on common drilling practices and field experience from mining, quarrying, and construction projects worldwide.
Understanding these classifications helps drilling professionals choose the right button bit for their rock conditions, drilling rig, and project requirements.
Related Reading：
FAQ
There isn't one fixed number because button bits are modular. Manufacturers like RockHound offer dozens of configurations by mixing and matching four main categories:
Thread Type: Compatibility with your drill rod (e.g., R32, T45).
Face Design: How the bit hits the rock (e.g., Drop Center, Convex).
Button Shape: The profile of the carbide inserts (e.g., Spherical, Ballistic).
Skirt Design: The body shape for stability or retrieval (e.g., Standard, Retrac).
Thread selection depends on the hole diameter and the scale of the job:
R-Series (R25, R28, R32): Ideal for small holes (28–64 mm), drifting, and tunneling.
T-Series (T38, T45, T51): Best for medium to large production holes (64–152 mm) in quarrying and bench drilling.
GT/ST Series (GT60, ST68): Designed for high-performance, large-scale mining and deep long-hole drilling.
Drop Center (Concave): Choose this for hole straightness. It features a recessed center that helps the bit stay on track. It is excellent for medium-hard rock and offers superior flushing.
Convex (Dome): Choose this for speed. It has a rounded face for aggressive penetration in soft-to-medium rock, though it may "wander" (deviate) in very hard formations.
It is a balance between service life and penetration rate (ROP):
Spherical (Round): The most durable shape. Use these for very hard, abrasive rock like Granite or Iron Ore. They drill slower but resist chipping and wear.
Ballistic (Parabolic): These are pointed and aggressive. Use these for soft-to-medium rock to achieve maximum drilling speed. Note that they wear out faster in abrasive ground.
A Retrac (Retractable) bit is essential for unstable, fractured, or collapsing ground. Unlike a standard bit, a Retrac bit has a tapered body with rear-facing cutting buttons. This allows the bit to "drill its way back out" of the hole if the rock collapses behind it, preventing jammed tools and lost equipment.
| Bit Type | Best Rock Condition | Key Advantage |
| Standard | Stable, Medium-Hard | General purpose, balanced performance. |
| Retrac | Fractured / Loosening | Prevents jamming; easy retrieval in "bad" ground. |
| Drop Center | Hard / Competent | Superior hole straightness and flushing. |
| Ballistic | Soft to Medium-Hard | Highest penetration rate (ROP). |
| Spherical | Very Hard & Abrasive | Maximum wear resistance and service life. |
