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. Depending on the nature of its work, we can also think of it as a tool.

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.

Whether it is in the selection of materials or the production process, we are all to improve the service life of the shank adapter. How to improve the service life of the shank adapter?

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.

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.

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.

Of course, improving the service life of the shank adapter is not only solved from the failure mode of shank adapter fracture but there are other forms of shank adapter failure. Judging and dealing with these failure modes is also essential to improving the service life of the shank adapter. Specifically, you can learn from the article “13 ways to solve the failure of the shank adapter “. The above is the whole introduction about what a shank adapter is and how to improve its service life. I hope to answer your doubts in this regard. We are also very welcome to contact us to understand.