What is a Shank Adapter? How to Improve Its Service Life?

Table of Contents

With the rapid development of high-frequency, high-power full-hydraulic rock drilling equipment, the rock-drilling process and conditions have changed, and the market has increased the matching and technical requirements for the shank rod in the supporting drilling tools. Therefore, a variety of shank adapters are produced correspondingly.

What is a shank adapter?

The shank adapter is an important part of the rock drilling tool. It directly bears the high-frequency impact and strong torsion of the rock drill during operation and transfers the impact energy of the rock drill piston movement from the end of the shank adapter to the drill rod and the drill bit for rock drilling operations. In short, the shank adapter is a part connected with the rock drill at one end and the drill rod at the other end.

shank adapter

Classification of shank adapters

shank adapters

There are three types of shank adapters: flange-type shank adapters, lug-type shank adapters, and spline adapters.

The cross-section of the flange-type shank adapter is hexagonal, with inner circle diameters of 22mm and 25mm, lengths 108mm and 159mm. Made by forging process and used for light rock drill.
The lug-type shank adapter is used for inner-rotating medium-sized guide-type rock drills, and the diameter of the drill rod is 25mm or 32mm.
The spline adapter is often used for heavy-duty guide-type external rotating rock drills with large torque, and the diameter of the drill rod is more than 38mm. Commonly made by machining methods.
No matter what kind of shank adapter it is, due to its harsh working environment and load complexity, people have higher requirements on the usability of the shank adapter. For example, in the choice of materials, the shank adapter material is 23 CrNi3Mo, because Cr and Ni elements can improve the hardenability of steel, make the overall performance of the shank adapter after quenching uniform, improve the overall strength and toughness, and can make the organization and performance of carburizing layer improved. The addition of Ni has a good effect on the quality of the infiltrated layer, which can avoid the excessive carbon concentration on the surface and make the concentration change smoothly, which improves the easy formation of more retained austenite in the carburized layer after quenching. It is necessary to reduce residual austenite in the process, and the addition of Mo can overcome the shortcomings of temper brittleness of Cr Ni steel. The carbon content of the steel is selected at 0.20%-0.35%, to make the core of the shank adapter in the heart after carburizing quenching have high enough strength, obtain the best hardening effect, and make the performance between the carburizing layer and the heart gentle transition, improve the service life of the shank adapter. The manufacturing process of the 23 CrNi3Mo steel shank adapter is: blanking → forging → normalizing → machining forming → carburizing → high-temperature tempering → quenching → low temperature tempering → fine grinding.

The function of the shank adapter

The shank adapter plays a vital role in rock drilling operations. Firstly, it withstands the high-frequency impact and strong torsion of the rock drill and is a bridge connecting the rock drill with the drill rod and drill bit. Secondly, the shank adapter transmits the impact energy of the rock drill piston movement to the drill rod and drill bit, so that the drill bit can drill into the rock smoothly. In addition, the shank adapter also withstands the reaction force from the rock, safeguarding the internal components of the rock drill from damage.

How to improve the service life of the shank adapter?

Selection of high-quality raw materials

The service life of the shank adapter is closely related to the quality of its raw materials. High-quality high-strength alloy steel material exhibits superior strength and toughness, capable of withstanding more impact and torque. Therefore, when choosing a shank adapter, priority should be given to products using high-quality alloy steel as raw materials.

Precision processing technology

The processing accuracy of the shank adapter also has an essential impact on its service life. Precision processing technology can ensure that the shank adapter’s shape, size, and surface quality meet standard requirements, reducing stress concentration and wear caused by poor processing. Therefore, when manufacturing the shank adapter, advanced processing equipment and processing processes should be used to ensure the quality and performance of the shank adapter.

Reasonable heat treatment process

Heat treatment is an essential means to improve the performance and service life of the shank adapter. Heat treatment processes such as quenching and tempering can enhance the hardness, toughness, and wear resistance of the shank adapter, improving its ability to withstand impact and torsion forces. Therefore, when manufacturing the shank adapter, reasonable heat treatment process parameters, and procedures should be formulated to ensure the performance and stability of the shank adapter.

Reasonably matched rock drill

The service life of the shank adapter is closely related to the matching degree of the rock drill. If the model and specification of the rock drill do not match, it will cause the shank adapter to bear excessive impact force and torque, thus shortening its service life. Therefore, when selecting a rock drill, a suitable match should be made based on engineering requirements, rock properties, and other factors to ensure that the shank adapter can function normally and stably.

Correct use

In addition to quality control during the manufacturing process, correct use is also a critical factor in improving the service life of the shank adapter. During use, you should pay attention to the following points:

  • Regularly check the appearance quality and wear of the shank adapter, and replace seriously worn shank adapters promptly;
  • Keep the shank adapter in good coordination with the rock drill, drill rod, and drill bit to avoid excessive gaps and looseness;
  • Maintain sufficient cooling water supply during use to lower the temperature of the shank adapter and reduce wear;
  • Clean and maintain the shank adapter regularly to remove dirt and rust on the surface and maintain it in good working condition.

Storage and care

When storing, the shank adapter should be placed in a dry and ventilated place to avoid moisture and corrosion. When maintaining, the shank adapter should be regularly lubricated and rust-proofed to maintain its good performance and service life.

In addition to this, as the last section of the drill tool, the shank adapter is inevitably subjected to the bending moment during rock drilling operations; at the same time, due to the reflection of the shock compression wave at the free end and the section change, a tensile stress wave will also be generated inside the shank adapter. The alternating action of impact compression and tensile stress, coupled with the corrosion of mineral water, will cause impact corrosion fatigue fracture of the shank adapter. The shank adapter fracture is the main factor affecting its service life, so to improve the service life of the shank, we can start by improving the impact fatigue strength at the notch of the shank adapter. The following two measures can be adopted.

1. Ensure the machining quality of recess of thread portion and the circular arc transition of sealing ring groove

The fracture of the shank adapter mainly occurs at the recess of the thread portion and the sealing ring groove of the inner hole. Most of the reasons for the problems in these two parts are that the machining quality of the arc transition is poor. Therefore, to improve the ability of the shank adapter to resist impact fatigue fracture, the machining quality of these fragile parts should be strictly guaranteed first.

2. The good carburizing heat treatment process ensures high notch impact bending fatigue strength of shank adapter material 

In machining, ensuring arc transition quality and reducing stress concentration can improve the fatigue resistance of the shank adapter. But local stress concentration is inevitable. Therefore, how to improve the notch impact bending fatigue strength from the material itself becomes another important aspect to improve the fatigue resistance of the shank adapter.

Conclusion

As an integral component of rock drilling tools, the service life of the shank adapter directly impacts work efficiency and cost. By employing various methods, we can effectively prolong the service life of the shank adapter, thereby reducing engineering costs and enhancing work efficiency.

In practical applications, we can also formulate more detailed shank usage and maintenance plans based on specific engineering needs, rock properties, and other factors to ensure that the shank adapter can work stably for a long time. At the same time, we should focus on the development and application of new shank adapter products in the market, continuously updating and improving our use and maintenance methods to align with evolving engineering needs and market conditions.

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