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The threaded extension rod is a hollow circular or hollow hexagonal rod with connecting threads at both ends or one end of the rod. It is the main part of the threaded connection rock drill tool. It has the advantages of wide application range, fast drilling speed, small impact energy transfer loss, high rock drilling efficiency, easy realization of mechanized drilling, and improvement of rock drilling conditions.
The main thread form of the threaded extension rod
1. Corrugated thread (R thread)
The main thread structure form.
Characteristics are as follows:
A. After surface strengthening treatment such as carburizing, it has sufficient wear resistance.
B. The loss of energy transfer is small.
C. The loading and unloading are more convenient.
D. It can be processed by a special lathe, and the manufacturing cost is low.
2. Compound thread (HL thread)
Characteristics are as follows:
A. Large pressure area, high energy transfer efficiency.
B. Slow wear, large allowable wear amount, long service life.
C. Convenient loading and unloading.
3. Trapezoidal thread (T thread)
The characteristics are excellent application performance and long drilling life. It has gradually become the main threaded connection structure with drilling tools for medium and large cross-section threaded connections.
Types of threaded extension rods
1. Extension rod
This is a threaded extension rod with the same nominal diameter of the thread and the hollow steel rod. The hollow steel does not need to be upset by hot forging, and the thread is directly formed by machining.
2. Light-weight extension rod
This type of drill rod is a threaded extension rod with the nominal diameter of the thread larger than the hollow steel. During processing, the end of hollow steel must be forged and upset before threading. During drilling, the reduction in the weight of drill rod is beneficial to improve drilling efficiency.
3. Drifting and tunneling rod
The drifting and tunneling rod is a threaded extension rod whose nominal diameter of the thread is greater than or equal to one end of hollow steel and equal to or less than the other end.
4. MF rod
This is a circular or hexagonal threaded extension rod with an internal thread at one end and an external thread at the other end. Because it combines the coupling sleeve and the drill rod, it reduced the weight of the matching rock drilling tool, shortened the thread connection length, and reduced the impact energy loss at the thread connection, the connection, replacement, installation, and removal are more convenient, the drilling speed is accelerated, and the drilling efficiency is greatly improved.
5. Other structural threaded extension rods
It includes guide rods and tube rods. They are not commonly used, and no further introduction.
Application of threaded extension rod
1. Different thread types
| Classification of thread | Nominal diameter applicable | Scope of application for rock drilling |
|---|---|---|
| Corrugated thread | 22、25、28、32、38 | Medium and small diameter rock holes |
| Trapezoidal thread | 38、45、51 | Medium and large diameter rock holes |
| Compound thread | 32、38、45 | Medium and large diameter rock holes |
| S thread | More than 51 | Large diameter rock holes |
2. Different structures
| Structure classification | Main mode of use | Main application of rock drilling | |
|---|---|---|---|
| Distribution of rock drilling holes | Rock hole depth | ||
| Extension rod | multiple connections | Upward fan hole, downward vertical hole, and oblique hole | middle、deep |
| Light-weight extension rod | |||
| Drifting and tunneling rod | single connection | Longitudinal horizontal hole and oblique hole | shallow、middle |
| MF rod | multiple connections | Upward fan hole, downward vertical hole, and oblique hole | middle、deep |
With the rapid development of modern rock drilling machines, high-frequency, high-power hydraulic rock drilling equipment has also been significantly developed. The market demand for thread drilling tools with medium and large cross-sections has increased accordingly, which has also promoted the rapid development of threaded drill rods.Manufacturers can combine domestic and foreign production experience to improve the thread drilling tools production technology, such as material selection, hollow steel production process, etc, so as to usher in a new era.
