Rock drilling tools play an important role in coal mining and tunnel construction. They are necessary tools for drilling and blasting and are also consumables. The rock drill bit is an essential part of the rock drilling tool, directly responsible for breaking down the rock mass. Its purpose is to fracture solid rocks by leveraging the impact generated by blades and teeth, creating rock holes of varying diameters. It consists of two major types, taper and threaded, according to the different connection methods. This article will introduce the definition, applications, and types of taper bits to help you understand it better.
What is a taper drill bit?
The taper drill bit is a lightweight rock drilling tool employing the tapered hole on the skirt body for linking with the cone of the tapered drill rod, facilitating the fracture of rock masses. Typically paired with a hand-held or outrigger-type light rock drill, it finds its niche in shallow hole drilling and sees primary application in mining, tunnel engineering, tunnel excavation, stone mining, and similar operational environments. This drill bit is designed to improve drilling efficiency and reduce drilling costs.
Types of taper drill bits
Taper drill bits include chisel bits, three-blade drill bits, cross bits, and tapered button bits.
Chisel bit
The manufacturing process of the chisel bit is relatively simple, easy to resharpen, reliable in operation, and has strong adaptability to rock mass properties. It is suitable for light internal combustion, electric, pneumatic, and hydraulic rock drills to drill rock holes with a diameter of less than D50mm in various types of rocks. Its disadvantage is that if the strength of the drill bit is low, it wears quickly and is easy to get stuck, which often causes damage to the drill bit and affects the progress. Consequently, it has gradually fallen out of favor and is now only encountered in a limited number of projects.
Three-blade drill bit
This particular drill bit is an evolution of the original chisel bit, featuring a discontinuous drill blade structure. Since the development of the three-edged drill bit, companies worldwide have engaged in continuous research and development, consistently unveiling three-blade drill bits based on this foundational structure. These iterations involve ongoing enhancements to both form and materials. In contrast to the chisel bit, the three-edged drill bit structure offers more breaking points, resulting in superior work quality. The use of carbide material in the tool head maximizes drilling performance, and the geometry is conducive to efficient production with radial resistance.
The three-edged drill bit boasts outstanding wear performance, high rotation speed that minimizes the risk of getting stuck, a prolonged re-grinding cycle, numerous, and an extended service life. However, it’s worth noting that the manufacturing process is relatively intricate, contributing to a comparatively higher cost. Despite this, the maintenance of the three-blade drill bit is simpler, reducing the overall maintenance workload during production and subsequently lowering production organization costs.
Practical experience has shown that the optimal diameter for the three-blade drill bit falls within the range of 32 to 40 mm. This type of drill bit demonstrates its highest production efficiency when applied to brittle rocks and solid, cracked rock formations.
Cross bit
Cross bits represent the predominant category within the flake series bits globally. Typically featuring a diameter ranging from 32 to 48 mm, these bits improve upon the three-edged drill bit design by incorporating an additional blade arranged in a cross shape. This innovation significantly enhances wear resistance, estimated to increase by approximately 30% to 50% compared to chisel bits. The stable geometry of cross bits, combined with simple processing technology, ensures reliable quality. At the same time, the brazing chisel’s broken point allows for convenient operation.
Cross bits exhibit strong adaptability to varying rock drilling conditions and are virtually unrestricted by the type of rock drilling machine or the rock body’s performance. In numerous mining projects worldwide, including countries like Sweden and Canada, cross bits and button bits have become commonplace replacements for chisel bits, underscoring their effectiveness and widespread adoption in the industry.
Taper button bit
The button bit is designed to adapt to high-power hydraulic rock drills, mainly to improve production efficiency and reduce labor workload. These bits predominantly incorporate carbide blades with a concentric design on the drill bit. The carbide teeth used in these bits come in various shapes, including spherical, tapered, and conical. Spherical teeth exhibit the highest wear resistance and strength, followed by conical spherical teeth, with conical teeth ranking lowest in these aspects. However, the efficiency of rock drilling is the opposite.
Given these considerations, choosing button bits should be based on different rock formations and equipment. In operational contexts, button bits are mainly responsible for the crushing work, with the typical failure mode involving cracked or even broken teeth. Consequently, in soft rock layers, it’s advisable to opt for low-strength conical tooth drill bits. In the medium hardness of the rock layers, a choice between spherical teeth or a combination of conical and intermediate teeth is suitable. In hard rock layers, the preference is for spherical tooth drill bits.
It’s crucial to note that the number of teeth is an essential structural parameter, varying across different types of button bits with different diameters. This variation in teeth number influences their performance under distinct working conditions. Practical experience has validated the application of such button bits in brittle, corrosive rock formations, characterized by their rapid drilling speed, high stability, production of coarse rock powder, and extended service life.
Selection of taper drill bits
When selecting a taper drill bit, there are several factors to consider to ensure it is suitable for your specific engineering needs.
- Geological conditions: different formations have different hardness, brittleness, and abrasiveness, so it is necessary to choose a taper drill bit suitable for the current geological conditions.
- Drilling process: different drilling processes have varying requirements for the type and specifications of the taper drill bit. Depending on the engineering needs, it’s essential to choose the appropriate drilling process and the corresponding taper drill bit.
- Budget and Cost: the price of a taper drill bit varies based on factors such as material, manufacturing process, and performance. When selecting a taper drill bit, it’s critical to consider the project budget and overall costs. Opt for a product with a higher price-to-performance ratio to ensure efficient use of resources while meeting project requirements.
- Brand and reputation: choosing a brand with a good reputation and reputation can ensure the stable quality and performance of the taper bit and reduce risks during use.
Recognizing the significance of the taper drill bit as a crucial rock drilling tool in infrastructure construction is essential. A comprehensive understanding of its definition, types, and applications is pivotal for using it effectively, leading to enhanced work efficiency and quality. With the continuous advancement of technology, we expect to see more efficient taper bits to meet the evolving requirements of the engineering field. Staying informed and adapting to these technological improvements will undoubtedly contribute to further advancements in work processes and outcomes.
