Retractable Thread Drill Bit: Solving the Bit Sticking Problem in Complex Formations
In rock drilling operations such as mining and tunneling, bit sticking (jamming) is one of the most frustrating problems for crews. After the bit penetrates, the rock cuttings generated by fracturing accumulate and become compacted between the bit body and the borehole wall — this not only prevents smooth withdrawal of the bit but can also damage the drill rod, seriously delaying the project schedule. The problem is especially severe in fractured, broken, or loose formations.
To address this industry pain point, we have launched the retractable thread drill bit (also known as the easy-return thread drill bit). This bit integrates the high-efficient rock breaking capability of cemented carbide buttons with the anti-jamming, easy-retract design of a reverse taper, solving the traditional problems of bit sticking and difficult withdrawal while significantly improving drilling efficiency and service life. Whether for mining or tunneling applications, our retractable thread drill bit provides a reliable solution.
1. Core Technology: Our Retractable Bit Body Design
The core of the retractable thread drill bit lies in our independently developed retractable bit body design.
The bit body is the steel part that connects to the drill rod. Traditional bit bodies are either straight cylindrical or have a positive taper, making them prone to jamming due to cuttings accumulation when withdrawing. Our retractable bit body, by contrast, adopts a reverse taper (back taper) design, presenting an “upper thick, lower thin” shape — the end near the thread (connecting to the rod) is thicker, while the end near the bit head (contacting rock) is thinner.
The advantage of this design is: during withdrawal, as the bit is lifted upward, a natural gap forms between the bit body and the borehole wall. The accumulated cuttings slide down quickly along the reverse taper slope, no longer wedging the bit — greatly reducing the risk of sticking.
Our retractable bit body also features the following technical characteristics:
The outer diameter of the bit head is 0–8 mm larger than the outer diameter of the bit body, effectively reducing friction between the bit and the borehole wall.
Several axial debris discharge grooves (straight or helical) are provided on the outer wall of the bit body, enhancing debris removal and preventing cuttings buildup.
Excellent debris discharge leads to higher borehole quality, significantly improving borehole straightness and roundness, thereby ensuring subsequent blasting results.
The above design makes our retractable thread drill bit especially suitable for loose rock masses and broken formations with poor integrity, effectively improving borehole straightness and assisting in drill tool retrieval.
2. Bit Material and Manufacturing Process
Superior bit performance comes from our insistence on high-quality materials and advanced processes.
2.1 High-Quality Raw Materials
We use high-strength alloy steel for the bit body, combined with cemented carbide buttons (typically tungsten carbide). The hardness of this cemented carbide far exceeds that of ordinary steel, enabling it to withstand wear and impact in hard rock — it is the core component for rock breaking.
2.2 Advanced Heat Treatment
We employ a carburizing heat treatment process, allowing the bit to meet rock excavation requirements at various hardness levels while minimizing energy loss during impact energy transmission. The energy is concentrated on the rock, achieving efficient penetration.
2.3 Precision Button Fixing and Assembly
We are equipped with advanced CNC machining equipment and a mature alloy button assembly process (hot press fitting / thermal shrinking technology), ensuring that the buttons are firmly fixed. The button loss rate is below 0.1%. Uniform fixing force reduces the risk of button loss or loosening, further ensuring drilling verticality.
2.4 Strict Quality Control
Every bit undergoes rigorous quality inspection before leaving the factory, ensuring you receive a truly high-quality rock drilling bit.
3. Bit Specifications and Selection Guide
Our retractable thread drill bits offer extensive options in multiple dimensions to suit different working conditions and equipment requirements.
Thread types available:
R22, R25, R28, R32, R35, R38, T38, T45, T51, T60, ST58, ST68, and various taper connections. Among these, R32, T38, T45, and T51 are the most common choices in mining and tunneling.
Bit diameters:
Our product range covers 38 mm to 152 mm.
Specific examples:
T38 bits: 64 mm, 76 mm, 89 mm, 102 mm
T45 bits: 89 mm, 102 mm
T51 bits: 89 mm, 115 mm, 127 mm
Different diameters suit different blasthole or anchor hole sizes.
Bit face types:
Flat face: For hard, abrasive rock (e.g., granite)
Concave face: For medium-hard rock, good straightness
Convex face: For soft rock, fast penetration
Button shapes:
Spherical button: Hard rock, high wear resistance
Ballistic button: Medium-hard rock, fast penetration
Conical button: Soft rock, high drilling efficiency
Parabolic / semi-ballistic button: Other specific conditions
Bit body types:
Standard body: For intact, stable rock
Retractable body (the core configuration of our retractable thread drill bit): Recommended for loose, broken, fractured formations to effectively prevent sticking
Heavy-duty body: For extreme conditions with high impact and high wear
4. Industry Applications
Our retractable thread drill bits are widely used with hydraulic drifters (or pneumatic rock drills) and corresponding drill rods, primarily in:
Underground mining: Ore body penetration, blasthole drilling
Open-pit mining: Bench blasthole drilling
Tunneling and subway projects: Rock blastholes, pipe roof support holes
Slope support and foundation anchoring: Anchor holes, cable bolt holes
In complex geological conditions such as fractured or broken zones, standard bits frequently suffer from sticking or even complete loss of the drill string, with a single loss costing thousands of RMB or more. Our retractable thread drill bit, with its unique reverse taper body design, reduces the sticking rate to a negligible level, dramatically lowering your drill tool loss costs while reducing withdrawal time and minimizing abnormal rod wear — delivering significant overall benefits.
5. Our Commitment
Every bit is made from high-quality materials with strict processes — reliable quality.
Professional bit selection guidance to help you match the most suitable bit model.
Custom bit production to meet special working conditions.
Comprehensive after-sales support with rapid response to any bit usage issues.
From design to production, from inspection to delivery, we focus exclusively on the rock drilling bit field. The retractable thread drill bit is our professional solution for tackling drilling challenges in complex formations — and our sincere effort to help frontline workers solve the real-world problem of bit sticking.
If you are interested in our retractable thread drill bit or need selection advice for your specific construction site, please feel free to contact us. With factory expertise and dedication, we look forward to providing you with high-quality rock drilling bits and technical support.
Let me know if you’d like a simplified short version for a datasheet or catalog.
