Rock drill bits are tools for drilling and rock drilling in hard materials such as rocks. They play an important role in construction, mining, tunnel construction, and more. According to different uses and characteristics, there are many rock drill bit types, each with unique advantages and scope of application.
According to the different rock-breaking mechanisms of the head blade and teeth, rock drill bits are divided into chip series and button series. In the chip series drill bit, according to the diameter, the number of drill blades, and the arrangement, is subdivided into four categories: chisel-shaped, three-edged, cross-shaped, and X-shaped.
According to different connection methods, there are two types of rock drill bits: tapered bit and thread bit. This classification is the most commonly used.
Tapered bit
Tapered drilling tools refer to a type of light rock drilling tools that use the taper hole of the skirt body to connect with the cone of the drill rod to realize the impact and rotation transmission of the rock drill. Tapered drilling tools include tapered bits and drill rods. Tapered bits include chip bits and button bits, and they are mainly used in mining, tunnel engineering, roadway excavation, stone mining, and other working conditions.
Chisel bit
It has a relatively simple manufacturing process, convenient regrinding, reliable work, and strong adaptability to rock mass performance. It is often used with light internal combustion, electric, pneumatic, and hydraulic rock drills to drill rock holes with a diameter of less than 50mm in various types of rock.
Three-edged drill bit
It is a small-diameter cored triple-edged drill bit with a longer service life, faster drilling speed, and straighter hole drilling than the chisel bit in the diameter range of D32~D45mm.
Cross bit
It is the main variety in the chip series. The diameter is in the range of D29~D48mm, which has strong adaptability to rock drilling conditions and is almost not limited by rock drilling models and rock mass performance.
Button bit
It started from the deep well button roller cone bit for oil drilling and the DTH button bit for deep hole drilling in mines. It has gradually developed into a wide range of large, medium, and small-diameter button bits for rock drilling.
Because of its reliable connection, it can transmit high torque and is easy to extend the drill rod, so it is commonly used on drilling frames or drill jumbos to drill deeper and larger diameter holes.
Chisel bit
It has two types of internal and external corrugated thread connections. External threads are used mainly for small drill bit diameters.
Cross bit
It has two types of internal and external thread connections. External thread connections are more used for small drill bit diameters and sometimes for large-diameter drill bits. Internal thread connections are the most widely used.
X bit
It is an internal thread connection and is mainly used for surface and underground post-rock drilling.
Button bit
Because of its long passivation period, it helps to save working hours, reduce the physical labor of workers and speed up the progress of the project. Therefore, threaded button bits with different diameters are widely used in various types of hard and brittle rocks to cooperate with drill jumbos for rock drilling.
The geometry of rock drill bits
The basic principles of geometric structure and parameter design of rock drill bits are effective rock breaking, timely powder discharge, stable shape, strong and wear-resistant, round and straight drilling, flexible rotation, reliable connection, convenient disassembly, easy manufacture, and beautiful appearance. Therefore, rock drill bits’ optimal geometric structure and parameters form the basis of the technical and economic indicators such as the drilling service life, drilling speed, carbide utilization rate, cost, and market competition. The material and manufacturing technology are all guaranteed around the geometric structure.
Parameters of rock drill bits
Tapered bit
| Rock drill bit type | Parameter |
| Chisel bit | D32(B22*7°)、D35(B22*7°、B25*12°)、D38(B22*7°、B25*12°)、D41（40、42）(B22*7°、B25*12°)、D43(B22*7°、B25*12°)、D45(B22*7°、B25*12°) |
| Three-edged drill bit | D32(B22*7°)、D35(B22*7°、B25*12°)、D38(B22*7°、B25*12°)、D41（40、42）(B22*7°、B25*12°)、D43(B22*7°、B25*12°)、D45(B22*7°、B25*12°) |
| Cross bit | D32(B22*7°)、D35(B22*7°、B25*12°)、D38(B22*7°、B25*12°)、D41 (B22*7°、B25*12°)、D43(B22*7°、B25*7°)、D45(B22*7°、B25*12°)、D48(B25*12°) |
| Button bit | D32 three-tooth (B22*7°)、D35 four-tooth (B22*7°、B25*12°)、D38 four, five-tooth (B22*7°、B25*12°)、D41（40、42）four, five, six-tooth (B22*7°、B25*12°)、D43 six-tooth (B22*7°、B25*7°)、D45 six, seven-tooth (B25*12°)、D48 seven-tooth (B25*12°) |
Threaded bit
| Rock drill bit type | Parameter |
| Chisel bit | D35(22R)、D38(22R、25R）、D41(25R、28R)、D43(25R、28R) |
| Cross bit | D35(22R)、D38(22R、25R）、D41(25R、28R)、D45(25R、28R)、D48(32R)、D51(32R)、D57(32R)、D64(32R、38R、38T) |
| X bit | D64(32R、38R、38T)、D70(32R、38R、38T)、D76(32R、38R、38T、45T)、D89(38R、38T、45T)、D102(38R、45T、51T) |
| Button bit | D35 four-tooth（25R)、D38 four, five, six-tooth（25R、28R）、D41(40、42) four, five, six-tooth（25R、28R）、D43 six, seven-tooth(25R、28R）、D45 six, seven-tooth (28R、32R)、D48 seven-tooth (25R、28R)、D51 nine-tooth (28R、32R)、D57 nine-tooth (32R)、D64 nine, ten, twelve-tooth (32R、38R、38T)、D70 eleven-tooth（38R、38T）、D76 ten, eleven, twelve, thirteen-tooth（38R、38T、45T、51T）、D102 eleven, fourteen, fifteen, sixteen-tooth（38R、38T、45T、51T）、D115 fifteen, seventeen, eighteen-tooth（45T、51T）、D127 eighteen-tooth（51T） |
How to choose rock drill bits?
When using a hand-held or outrigger light rock drill and a small-diameter drill bit for shallow hole drilling, adopt tapered drilling tools. When the diameter of the drill bit is large, and the drill frame and rock drilling rig are used underground or in the open for medium and deep rock drilling, adopt threaded drilling tools.
Selection of cemented carbide grades
Various rock drill bits and geological formations typically correspond to specific cemented carbide grades for optimal compatibility.
- The higher the uniaxial compressive strength value of the rock, the greater the toughness. In order to prevent the blades and teeth from breaking, it is advisable to choose alloys with higher cobalt content and higher strength.
- For brittle rocks with low uniaxial compressive strength but high corrosion resistance, it is advisable to use carbides with lower cobalt content and higher hardness.
- For extremely tough rocks whose uniaxial compressive strength exceeds 300MPa, it is advisable to choose specialized carbide grades exhibiting enhanced toughness and containing 10% to 15% cobalt. However, in cases where the rock is highly abrasive, maintaining a moderate cobalt content is crucial.
Selection of rock drill bit diameter
- Select the rock drill bit diameter required for drilling and blasting: the diameter of the blasting hole is determined according to the diameter of explosives and detonation equipment needed for the blasting project; the diameter of the anchor bolt hole is determined according to the diameter of the anchor bolt and anchoring method, generally proposed by the engineering department.
- Select the appropriate rock drill bit diameter according to the impact energy of the rock drill.
As an indispensable tool in modern engineering construction and mining, rock drill bits improve work efficiency and promote the development of these industries. Different types of rock drill bits play unique roles in various fields. After reasonable selection and use, they can better fulfill rock drilling tasks and contribute to the development of industries.
