Rock drill bits are the tools for breaking rocks in the percussion rock drilling system, and their quality directly affects the economic benefits of the enterprise. The requirements of rock drilling are reasonable shape and structure, fast rock drilling speed, strong wear resistance, sufficient mechanical strength, good powder discharge performance, long service life, convenient manufacturing and repair, and low cost. In the coal mining project, there are chisel bits, cross bits, button bits, and carbide composite chip bits used in rock drilling.
Chisel bit
Chisel bits are the earliest and most widely used rock drilling tools in mining engineering. The working part of drill bit is a straight carbide blade. Its structure is simple, easy to process, and low in cost. It is suitable for rock drilling of tough overall rocks and has been widely used in mining engineering. However, its main problems include low drill bit strength, fast radial wear, easy to jam drill bit; the working part of drill bit is a whole blade with a circular arc, and the radius of the edge arc and the height of the piece are too large, once the piece is off and fragmented, drill bit will be scrapped early; the taper hole is too shallow, the connection between the drill rod and drill bit is not firm, easy to break or block the water hole in the work; poor powder discharge system, the diameter difference between the small and large ends is too small, easy to block and stick the drill, so the drilling speed is low, fast wear, easy to appear inverted cone phenomenon; the resharpening cycle of drill bit is short, the number of regrinding is less, and the production efficiency is not high.
Cross bit
The wear resistance of the cross bit is 30%-50% higher than that of the chisel bit. It has a stable geometric shape, relatively simple processing, good quality fixed button, convenient operation, and strong adaptability to rock drilling conditions. In mining, this type of drill bit is mainly suitable for tough, fractured, and abrasive rocks.
Button bit
Button bit was developed with the rapid development of high-power hydraulic rock drills to meet the need to improve productivity and reduce the labor intensity of workers.
Button bit has a new design for the shape of the carbide blade and its position distribution on the drill bit. The button types used for drill bits are mainly conical, parabolic, and ogive. Different button types of button bits should be selected according to different rock hardness and rock drilling machines.
According to the number of buttons, there are many types of button bits, and the number of buttons is closely related to the diameter, structure, and impact energy of drill bit. This type of drill bit is mainly suitable for brittle and abrasive rocks, and its main advantages are fast drilling speed, stable work, good blast hole quality, and coarse rock powder. The service life of button bit is about 3 to 5 times that of chisel bit, and it saves time, effort, labor, and materials.
Carbide composite chip bit
Cemented carbide composite chip bit is a newer type of rock drilling tool developed and designed by absorbing the advantages of the above-mentioned drill bits. It overcomes the defects of flake blades and button blades and concentrates the advantages of cross and button bits in rock drilling. Compared with the traditional drill bit, the cemented carbide composite chip bit has the advantages of fast speed, long service life, less grinding, stable quality, saving carbides and steel, and low cost. Its main technical and economic indicators exceed the traditional chip shape and button series rock drilling tools.
To sum up, in mine excavation construction, because of the influence of geographical environment, rock properties, and other conditions, the stress of various drill bits is more complicated, the failure forms are different, and the service life is different, so the type of drill bit must be selected reasonably according to the corresponding working environment and the drilling ability of the rock. In addition, the working conditions of rock drills and workers should be considered to minimize the labor intensity of workers and the consumption of drill bits to obtain high economic benefits.
