The button bit is a drilling tool widely used in geotechnical engineering. It has the characteristics of high efficiency, durability, and strong adaptability. The vital parameters of the button bit are related to its service life. To better understand and use the button bit, this article will introduce the essential parameters of the button bit.
Geometry of button bit
The geometric dimensions of button bit include inclination angle β, clearance angle α, and blade height H, which have a great influence on the service life of button bit.
Inclination angle β
Gauge buttons bear a large bending moment, so whether its design is reasonable or not directly affects the service life of drill bit. To reduce the force and radial wear of gauge buttons, and to prevent broken buttons and clamping, they should be inclined outward. Fixing technology requires sufficient steel wall thickness around the carbide to provide “holding force” and “supporting force”. In this regard, the larger the inclination angle, the better. However, when the inclination angle β is greater than 35°, it is easy to lose and break teeth.
Clearance angle α and blade height H
Clearance angle α is also called reaming angle. A large clearance angle is helpful for slag removal and prevents the drill from being stuck, but if it is too large will lead to faster radial wear and lower service life. It must be determined according to the crushing characteristics of the ore rock. When drilling soft rock, sufficient slag removal should be considered; for hard and highly abrasive rock, radial wear should be reduced as much as possible.
The blade height H should not be too large, which is conducive to increasing the length of the threaded connection and the contact length of the taper hole so that the contact is reliable and the stress is reduced to prevent the occurrence of broken pants and swollen pants.
Determination of powder discharge slot
Rock slag broken by impact rock drilling, if not removed from the bottom of the hole in time at the moment it is produced, will be crushed again, which not only reduces the speed of rock drilling but also increases the hazardousness of rock dust.
For medium-hard or below medium-hard rocks, the powder discharge slot is an important factor affecting the rock drilling speed. As long as the carbide strength allows, reducing the number of buttons and increasing the powder discharge slot will help to improve the perforation speed. In hard rocks, the wear resistance of carbides and the strength of skirt body should be considered first. In short, different types of powder discharge slots should be designed according to different rock conditions.
Button parameters
Number of buttons and button diameter
The number of carbides in drill bit is one of the most important parameters, which is related to the diameter of drill bit, the form of the structure, and the size of the impact power transferred. It should meet two conditions: the lowest power consumption per unit volume of rock crushed and sufficient strength of carbides.
The size of button diameter usually considers the following three factors: sufficient fracture resistance, solidity of the fixed buttons, and the possibility of button distribution.
The reasonable distribution of buttons has a significant impact on the performance of drill bit. The basic principles of button distribution: are effectively crushing, reasonable burden; uniform wear; solid button; convenient repair and grinding; no rock wall.
Button shape selection
Carbides are subjected to comprehensive effects such as cyclic alternating loads, repeated bending moments, torques, and impacts during work. It has a conical button, parabolic button, and ogive button. Conical button is high drilling efficiency. Parabolic button feeding speed is fast, which can not only ensure a certain rock drilling efficiency but also have a better service life. Ogive button is a fast button feed speed and excellent rock drilling efficiency.
Water hole
The position, quantity, and size of water holes are also directly related to the slag discharge efficiency and the wear of cemented carbide. The total area of the cross-section of the water hole should be equal to or greater than the cross-sectional area of the center hole of drill rod. The position of the water outlet of water hole on the side of drill bit should be as close as possible to the end of the outer edge of drill bit to ensure that the water flow can directly reach the fundus and quickly wash away the broken rock particles around the fundus to reduce repeated crushing. At the same time, concealed water outlets should be used as much as possible to effectively prevent deformation and blockage of the water outlets during the whole service period. Open the water outlet in the powder drain and close to the root of carbides. The jet angle of the side water hole is generally 30°~40° with the center line, preferably no more than 45. The jet angle of the water hole in the part is generally 15~25 with the center line preferably not more than 30°.
Diameter
Diameter is the main specification parameter of button bits, which determines the diameter and efficiency of the drilled holes. Depending on the application requirements, the diameter of the button bit can range from tens of millimeters to hundreds of millimeters. Choosing the appropriate drill bit diameter is critical to ensuring drilling quality and drilling efficiency. When selecting the drill bit diameter, factors such as the purpose of drilling, the characteristics of the rock, and construction conditions need to be considered.
Mechanical properties
Mechanical properties are crucial indicators for assessing the quality of button bits. These properties primarily include hardness, tensile strength, compressive strength, flexural strength, and toughness. These performance parameters directly impact the button bits’ service life and drilling quality. High-quality materials and advanced technology can ensure that the button bit has excellent mechanical properties and can maintain good working conditions and service life in various complex environments. When selecting a button bit, we should pay attention to whether its mechanical performance parameters meet the actual needs to ensure the smooth progress of the project.
Conclusion
The vital parameters of button bits directly affect its performance and use. Therefore, when selecting and using button bits, we should comprehensively consider the impact of these parameters based on engineering needs and actual conditions to ensure the efficiency and safety of drilling operations. At the same time, strengthening quality inspection and maintenance work can detect and deal with potential problems in time, which is also an important measure to ensure the button bits’ performance and service life.
