Although rock drilling tools are a general term for various product types, their main parts are mainly rock drill bits and drill rods. Although the coupling is also a member of the rock drilling tool family, it’s less popular than the drill bit and drill rod, so is it unnecessary? Can we first understand what a coupling sleeve is?

The coupling sleeve is a sleeve-like part with an internal thread for connecting the shank adaptor and the drill rod or two drill rods. Its classification and characteristics can refer to the following three:

Half-bridge coupling sleeve: There is a small bridge area without thread in the middle; the drill rod thread cannot pass through the middle of the coupling sleeve; the bridge area where the end of the drill rod is against the coupling sleeve; the half-bridge coupling sleeve is most suitable for high-torque equipment; most the wave thread and the stepped thread coupling sleeve are half-bridge type.

Full bridge coupling sleeve: avoid the possibility that the coupling sleeve slowly penetrates the joint along the thread; usually used for outdoor construction; it has the characteristics of better disassembly, and the connection is relatively tight; the probability of being stuck is small.

Conversion coupling sleeve: The two ends of the coupling sleeve have different thread specifications, commonly known as the reducing coupling sleeve, which is used for the connection between products with different thread specifications, and is only used under special circumstances.

Since the coupling sleeve is relatively simple compared to the drill bit and the drill rod, most manufacturers or users do not pay attention to it, and there is very little information about it that can be found online. From the above content, we can also see that the coupling sleeve is still very necessary. Don’t ignore it because it is too simple, or even throw it away when you find that there is a problem with it. Although it is simple, it does sometimes fail. Today, we will mainly share 15 ways to solve the failure of the coupling sleeve.

1. The solution to the coupling sleeve end is chipped, cracked, or flared caused by the drill rod not being firmly seated into the coupling sleeve from the mismatch of threads: It is important to standardize on a single source supplier for components to ensure proper thread tolerance. Don’t mix to match.

2. The solution to the coupling sleeve end is chipped, cracked, or flared caused by mixing old thread components with new ones: Install new coupling sleeves with new drill rods.

3. The solution to the coupling sleeve end is chipped, cracked, or flared caused by misalignment of feed: Check affected equipment.

4. The solution to the coupling sleeve end is chipped, cracked, or flared caused by overheating of the coupling sleeve: The maximum running temperature for coupling sleeves is 182℃.

5. The solution to the coupling sleeve end is chipped, cracked, or flared caused by improper heat treatment: Forward for analysis.

6. The solution to the coupling sleeve end is chipped, cracked, or flared caused by the drop of the drill rod when retracting on up holes: Use a rock drill with a shank adapter thread engaged to lower steel.

7. The solution to the coupling sleeve end is chipped, cracked, or flared caused by starting percussion or rotation with the end of the shank adapter resting against the end of the coupling sleeve： Do not engage percussion or rotation if the shank adapter thread end is not aligned inside coupling sleeve.

8. The solution to the failure across the thread section caused by hole deviation or misalignment of the feed-in about the hole direction: Employ straight hole drilling devices.

9. The solution to the failure across the thread section caused by low feed pressure: Monitor feed force and tune to conditions.

10. The solution to the failure across the thread section caused by the heavy rotational loads from drilling with dull bits: Resharpen the bits when the wear flats appear 1/3 dull or discard them when tungsten carbide button height is compromised.

11. The solution to the failure across the thread section caused by the surface layer of the drill rod compromised by nicks or dents: Avoid hammering on the connection. Use a breakout plate to loosen joints. Employ proper care and handling.

12. The solution to pitting or galling in the threads caused by unused blow energy being reflected and absorbed: Adjust percussion and feed pressures to rock conditions.

13. The solution to pitting or galling in the threads caused by drilling with dull drill bits: Resharpen bits when the wear flats appear 1/3 dull or discard them when carbide profile height is compromised.

14. The solution to split coupling sleeves caused by drilling with worn threads: Replace coupling sleeves more frequently.

15. The solution to split coupling sleeves caused by excessive feed pressure: Monitor feed force and tune to conditions.

The reason for the failure of the coupling sleeve is not that there is a problem with the coupling sleeve itself, nor is it that a new coupling sleeve can solve the fundamental problem. From the above solutions, we can see that most of them are caused by the user’s selection of equipment during operation, improper use, or the thrust of the current equipment that is not suitable for the ground conditions. We have also shared with you the methods to solve the failure of drill bits, drill rods, and shank adapters, in which we also repeatedly mentioned the problem of improper operation. Therefore, I would like to remind everyone again to improve production efficiency and economic benefits of the enterprise, no matter what kind of drilling tool fails, direct replacement is not the only way to solve the problem. In addition to eliminating the possible problems of the product itself, the correct operation and regular inspection of each component and equipment are very important, which requires enterprises to have complete operating procedures or drill tool suppliers can provide professional consulting for enterprises.