The Structure of DTH Drill Bit

Table of Contents

With the development of deep-hole blasting and mining technology, DTH drill bits are widely used because of their high efficiency, safety, and environmental protection, simple structure, and easy operation. However, the harsh working environment of the DTH drill bit and some uncontrollable reasons can easily cause damage to the rock drill bit and seriously affect the service life. To maximize the advantages of DTH drill bit and prolong its service life, manufacturers can further improve its performance by studying the structure of DTH drill bit.

DTH drill bit is mainly composed of a skirt body, shank adapter nylon tube, carbides, and powder discharge air blowing system.

DTH drill bit

Skirt body structure

The skirt body mainly plays the role of transmitting stress shock waves, holding and fixing carbides, and transmitting torque. The skirt body structure of DTH drill bit is equivalent to the spline stepped shaft parts, which undertake the function of transmitting torque, but it is different from ordinary spline shaft parts, which also have to bear high-frequency axial force from the DTH hammer while transmitting torque, the working environment is extremely harsh.
When designing the structural parameters of the connection part of DTH drill bit, we must pay attention to the size-matching relationship of the spline. The dimensional accuracy of mining drilling tools is generally considered not very high, and thus the fit relationship between the elements in the design and processing process is easily ignored, especially by those manufacturers who cannot produce DTH hammers. To ensure that the drill bits produced by the enterprise can be compatible with hammers produced by other companies, it often adopts a large clearance fit, and the existence of this clearance makes the drill bit extremely vulnerable to the additional instantaneous circumferential impact force from the spline sleeve of the hammer during use, and the larger the clearance the more obvious this impact effect is. When the peak shear force generated by this circumferential impact plus the positive stress caused by the high-frequency axial impact force exceeds the permissible stress of skirt body material, it is easy to cause the drill bit skirt body fracture or collapse block and carbides fracture and other phenomena, the service life of drill bit will be greatly affected. In addition, if the matching clearance is too large, it will also cause energy loss during the working process of drill bit and reduce production efficiency. Therefore, we must be careful when determining the parameters of drill bit connection part. While ensuring product interchangeability, we should take as small a clearance fit as possible to reduce the energy loss of the hammer and the damage to the drill bit.

Carbides

carbides

Cemented carbides mainly bear the high-frequency stress wave from the hammer, and directly transmit the high-frequency stress wave to the rock surface to participate in the cutting work. The stress of carbide is extremely complicated during work, especially the gauge button, under the action of high-frequency impact force, generates bending moments and torques, which can easily cause a broken button. Therefore, the carbide grade and button shape as well as the distribution of carbides should be considered comprehensively when designing the drill bit, and the corresponding carbide should be selected for different rock hardness, different geological structures, and the actual working conditions of the drill bit.

Powder discharge air-blowing system

The powder discharge air blowing system of DTH drill bit is composed of the end hole of drill bit, the blowing hole on the top surface, and the powder discharge grooves on the top and side. There is a certain matching relationship between the top-blowing holes and each element.
The depth of the powder discharge groove should generally be selected according to the working air pressure, rock hardness, and other factors. The higher the working pressure or rock hardness, the smaller the depth of the powder discharge groove can be. Otherwise, it can take a larger value.
There are many factors affecting the service life of DTH drill bits, and structural factors are only one of them, but structural factors belong to the source factor, which directly affects the quality of DTH drill bits. Only by carrying out research in various aspects under the premise of guaranteeing the quality of DTH drill bit, it is possible to maximize the service life of DTH drill bit.

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