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About dth bits

Types of DTH bits

Direct Down Hole (DTH) bits are available in various forms for specific mining needs.

  • Crown DTH Bits:

    The most common bit type, Crown bits, have a concave spherical or circular shape on their cutting surfaces. They feature a central pilot hole, followed by gaged rings and a flush port. The pilot hole initiates the drilling, while the gaged rings ensure hole diameter control. Flush ports allow for air or water circulation to remove debris and cool the bit. Crown DTH bits are widely used in various geological conditions and are suitable for different rock formations. They offer good hole quality and drilling efficiency.

  • Convex Crown DTH Bits:

    Similar to crown DTH bits, but with a convex (outward curved) cutting face design. This design allows for better weight distribution and reduced bit wear, especially in hard rock formations. They provide efficient drilling and good hole control.

  • Conical DTH Bits:

    Have a conical shape with a tapered cutting face. They are suitable for creating blast holes for mining and water well drillings.

  • Sand DTH Bits:

    Specifically designed for drilling in sandy or unconsolidated formations. They typically have a spherical or dome-shaped protrusions (teeth) pattern on the cutting surface. The teeth help to stabilize the borehole and prevent collapse in loose soil conditions.

  • Reaming DTH Bits:

    Equipped with teeth or pads, DTH reamer bits expand existing boreholes. They work by following pre-drilled holes and increasing their diameter. DTH reamer bits are useful for creating larger openings for production wells, pipeline crossings, or geological investigations.

  • Pilot DTH Bits:

    Smaller bits used to create the initial holes or pilot holes in a drilling program. Once the pilot hole is established, larger production DTH bits may be used for subsequent drilling.

  • Button DTH Bits:

    These bits drill rock with the use of buttons instead of blades. They have a more extended life expectancy, though it may take longer to drill with these types of DTH bits. DTH bits come in standard and modified button DTH bit configurations. Standard button DTH bits have a smooth button design, while modified button DTH bits have a more button design.

Specifications and maintenance of DTH bits

Specifications

  • Sizes

    The Down-The-Hole bits come in different sizes, with an outer diameter ranging from 3 to 36 inches.

  • Shank

    It is the part that connects the hammer and the bit. The DTH shank comes in different forms and sizes, such as Asahi shank, SD shank, HD shank, and others, which are compatible with various DTH hammers.

  • Count and arrangement of teeth

    The DTH bits have high-temperature-resistant teeth, which typically get arranged in a conical or triangular shape. Typically, there are 7, 11, 13, or more teeth on the bit.

  • Material

    Many DTH bits are usually made of alloy steel, carbon steel, and other materials.

Maintenance

  • Keep the clean bit

    After use, wash the bit with clean water. Use an air compressor or a blowgun to blow out residual debris and moisture inside the bit, ensuring it is dry and clean.

  • Inspect the bit

    Regularly check the state of the bit. Look for issues such as broken, deformed, or worn teeth. Also, check whether the shank has cracks or deformations and timely repair or replace the damaged bits if any is found.

  • Lubricate the bit

    Apply an appropriate amount of lubricant to the moving parts and connection portions of the DTH bit after cleaning and inspection. Lubrication can reduce wear and improve the bit's operating efficiency.

  • Store properly

    When not in use, store the DTH bit in a dry and clean storage place. Avoid exposure to the sun or getting wet, thus preventing rust and damage.

Usage Scenarios of DTH Bits

Since their introduction into the drilling industry, DTH bits have become invaluable across many mining and construction sectors. They are the gold standard for creating high-quality blast holes in various types of rock. Their ability to maintain hole diameter even at great depths makes them ideal.

  • Mining Industries: In the mining industry, DTH bits are used for creating blast holes in open-pit mines and underground tunnels. In open-pit mines, precise drilling patterns are crucial to ensure controlled blasts that minimize rock fragmentation. DTH bits enable miners to achieve accurate hole dimensions and depths, facilitating efficient blasting and extraction processes.
  • Water Well Drilling: DTH bits play a vital role in the exploration and construction of water wells. These bits can penetrate hard rock formations to reach water tables deep underground. Using DTH bits, drillers can quickly and precisely create wells, guaranteeing access to invaluable water resources for both domestic and agricultural irrigation purposes.
  • Geothermal and Oil Rifting: In the oil and geothermal industries, the reliability and precision of DTH bits are paramount. In oil extraction, DTH bits drill into potential oil reservoirs, navigating complex geological formations. Similarly, in geothermal energy production, these bits create wells that tap into geothermal reservoirs for sustainable energy generation. Their durability and accuracy make them indispensable in these resource-intensive applications.
  • Tunneling and Civil Engineering: Tunneling projects in civil engineering call for drilling holes for anchor systems, rock bolts, and drainage. DTH bits are essential in creating these holes, ensuring the stability and safety of tunnels and underground structures. Whether drilling for rock anchors to support tunnel walls or holes for drainage systems, DTH bits provide precise and reliable drilling solutions.
  • Construction: The construction industry also benefits from DTH bits. These bits drill foundation holes for large-scale construction projects, such as constructing bridges, buildings, and wind farms. The precise and efficient drilling offered by DTH bits contributes to the stability and integrity of these foundational elements.

How to Choose DTH Bits

Choosing the right DTH drill bits for the hammer is a job that requires careful research and assessment of the relevant factors. To ensure optimal drilling performance and a good cost-benefit ratio, it is essential to consider the rock formation, desired hole specifications, bit design features, and quality.

  • Rock Formation Analysis:

    The first step in selecting a suitable DTH bit is to analyze the geological conditions of the drilling site. The rock type and its structural characteristics need to be examined carefully. Different kinds of rock formations, such as consolidated formations (granite, basalt, limestone,etc.), soft to medium-hard formations (sandstone, siltstone, calcium, etc.), and fractured or heavily chiseled formations need to be taken into consideration.

  • Size and Depth Specifications:

    Specify the dimensions of the drill holes and the drilling depth required. Determine the diameter and depth of the hole needed for the specific application. This will help to choose the DTH bit that can meet the hole specification.

  • Bit Design Features:

    Consider the particular functional attributes of the DTH drill bits. Select the shape and design of the bit that suits the application. For instance, multi-cone bits are well suited for oil and gas exploration drilling, while PDC bits are more appropriate for water well and coal bed methane drainage vertical drilling. Besides, it is also necessary to consider the material used in the bit. Tungsten carbide inserts offer better wear resistance and longer life than conventional steel inserts.

  • Quality:

    Finally, it is essential to ensure the quality of the DTH bit selected to guarantee its reliability and lifespan. Choose a supplier with a proven reputation and good after-sales service. Consider the warranty offered by the manufacturer to ensure that the bit is protected from defects during the warranty period.

Q & A

Q1: Which type of rock can a DTH bit drill?

A1: The design of DTH bits makes them ideal for drilling into hard and abrasive rock formations. Such rock formations include granite, basalt, quartzite, sandstone, limestone, and schist.

Q2: How deep can a DTH bit drill?

A2: The bit diameter and boost pressure determine the drilling depth when using the DTH drilling technique. The standard DTH bits can achieve a depth of 20 meters to 30 meters per drilled hole.

Q3: What is the advantage of DTH bits?

A3: The rear-circulating water DTH bits offer improved flushing efficiency, reduce wall stick, and enable high-rate water flow through the bit. These bits are preferable in soft-to-medium formations requiring high penetration rates and good hole quality.

Q4: What's the penetration rate of DTH bits?

A4: The penetration rate of DTH bits varies depending on factors like the rock type, the power of the hammer used, the bit design, the bit diameter, the level of operator expertise, and the equipment maintenance. In ideal conditions and using the appropriate specifications, the DTH bit can achieve a penetration rate of 20 to 100 cm per minute in hard rock.