Types of Down-the-hole Drilling Tools

Table of Contents

Down-the-hole drilling tools are commonly used drilling equipment in engineering construction. They are widely used and come in many types. It has different models and kinds according to the specific application requirements and working conditions. This article will introduce the characteristics and types of down-the-hole drilling tools.

What is a down-the-hole drilling tool?

DTH drilling tools

The down-the-hole drilling tool uses compressed air as the power source. It immerses the rock drilling impact power part into the rock drilling hole and controls the piston to reciprocate through the impactor’s gas distribution device to impact the down-the-hole drill bit arranged at the front end of the hammer, a rock drilling equipment that transmits impact energy to the drill bit, and the drill bit breaks the rock. This tool finds widespread applications in various settings, including open-pit and underground mines, quarries, hydropower projects, water well drilling, mineral exploration, rock anchoring, geothermal excavation, subway engineering excavation, side pile support, and other construction sites.

Characteristics of down-the-hole drilling tools

Down-the-hole drilling tools have the following characteristics:

  • High straightness of drilling holes and smooth hole wall.
  • Good rigidity of drill pipe and hammer, not dependent on high axial thrust.
  • Drilling depth is not limited.
  • It has a simple structure and easy operation.
  • Low investment in equipment, easy to maintain.

Types of down-the-hole drilling tools

Down-the-hole drilling tools mainly include DTH hammers, DTH drill bits and drill pipes.

DTH hammer

DTH hammer

DTH hammer is an integral part of DTH drilling rig to connect DTH drill bit and drilling rig. It is widely used in metallurgy, coal, chemical industry, mining, water conservancy, hydropower, highway, railway, national defense, construction, and other engineering hole forming operations.

Down-the-hole hammer is an essential part of the down-the-hole drilling rig, its quality directly affects the drilling speed and drilling cost. Therefore, the most basic requirements for down-the-hole drilling rigs for down-the-hole hammers are high-performance parameters and high drilling efficiency; simple structure, easy to manufacture, use, and maintain; reliable operation of parts and long service life and the ability to function normally in various rock formations work.

DTH drill bit

DTH drill bit

The DTH drill bit is a kind of drill tool connecting the impactor with the spline of the drill bit to guide and transmit the rotation energy for the impact, with the drill bit and the DTH hammer diving into the hole to break the rock. It is mainly used in large open-pit mines, underground ore mining, anchoring engineering, quarrying, construction engineering rock drilling, and large-scale engineering construction.

During the drilling process, the upper end of the drill bit bears the impact of the piston, and the lower end hits the rock. It also withstands the abrasive effects of axial pressure, torque, and rock bumps, so the stress state is very complex. Therefore, the drill bit material is required to have high dynamic load strength and excellent wear resistance; the structure should facilitate the entry of compressed air into the bottom of the hole to cool the drill bit and remove rock ballast; the shape should be simple and easy to manufacture; the ratio of the weight of the drill bit to the weight of the piston should be as close as possible to 1, to improve the transfer efficiency of impact energy.

Many factors affect the performance and service life of a drill bit, including the structural design of the drill bit and the selection of material; the quality, shape, tooth fixing process of the carbide, and the drill bit usage and grinding system, etc.

Drill pipe

The function of the drill pipe is to send the DTH hammer to the bottom of the hole, transmit torque and shaft pressure, and deliver compressed air to the hammer through its center hole. The drill pipe experiences a combination of intricate loads, including impact vibration, torque, and axial pressure. Simultaneously, its surface is affected by the abrasive action of sandblasting caused by the rock slag discharged between the hole wall and the drill pipe. Consequently, the drill pipe is mandated to possess ample strength, stiffness, and impact toughness. Additionally, the diameter of the drill pipe must adhere to the specifications for effective slag discharge.

To sum up, different types of down-the-hole drilling tools have their unique characteristics and scope of application. We can select appropriate down-the-hole drilling tools based on actual needs, which can improve the efficiency of rock drilling and provide better support and protection for engineering construction.

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