Repairing copper nut wear after long-term use requires a comprehensive assessment based on the degree of wear, usage scenario, and cost-effectiveness. Common repair methods include machining, surface hardening, material filling, and lubrication optimization.
If the copper nut is only slightly worn and has not caused thread failure, mechanical repair can be used to restore its precision. For example, re-tapping can be used to rethread the worn hole using a tap that matches the original thread specifications, followed by replacing a new screw with the appropriate thread. This method is suitable for applications where the wear layer is thin and the thread depth still meets the standard, but the machining angle and verticality must be strictly controlled to avoid further damage due to improper operation. For nuts with uneven wear, a combination of grinding and polishing can be used. Metallographic sandpaper can be used to gradually polish the tooth surface, remove local scratches, and then smooth the surface to restore the tightness of the thread fit.
When the surface hardness of copper nuts decreases due to long-term wear, surface hardening can significantly improve their wear resistance. Metal anti-wear repair technology uses nanomaterial lubricant additives to form a chemically bonded protective layer on the friction surface. For example, nanoparticle lubricants containing inorganic elements, metal sulfides, or rare earth compounds can be used. Their high diffusivity and surface effects compensate for wear notches. This technology can enhance surface strength without changing the nut's dimensions and is particularly suitable for equipment operating at high speeds or high temperatures. If wear is accompanied by material fatigue cracking, heat treatment of the nut can be considered. Adjusting the quenching temperature and tempering process can eliminate internal stresses and slow crack growth.
For copper nuts with extensive wear and insufficient thread depth, material filling repair can quickly restore their function. Threaded sleeve installation technology involves pressing a prefabricated metal threaded sleeve into the worn hole, creating a new standard threaded connection. This method is simple to operate and provides stable repair results, but ensures that the threaded sleeve material is compatible with the copper nut substrate to avoid electrochemical corrosion. If the equipment requires extremely high nut strength, cold welding can be used to fill the worn area. Using high-hardness stainless steel welding consumables for low-temperature welding reduces the risk of thermal deformation and creates a repair layer with a strong bond to the substrate.
Lubrication optimization repair slows wear by improving friction conditions and is suitable for preventive maintenance or mild wear scenarios. Specialized lubricants containing anti-wear additives, such as electrolytes containing nano-alumina particles or urea complexes, can form a shear-resistant lubricating film on the threaded surface, reducing friction and filling minor scratches. For applications subject to frequent impact loads, solid lubricant coatings can be employed. Materials such as molybdenum disulfide or polytetrafluoroethylene can be sprayed onto the nut surface. Their self-lubricating properties effectively absorb vibration energy and extend the nut's service life.
In actual repair, a comprehensive decision must be made based on the cost of equipment downtime, the difficulty of nut replacement, and the economic viability of the repair. For example, copper nuts on large presses, due to their unique size and high replacement costs, can be repaired using jet electrodeposition technology for localized repair. Using a CNC system to precisely control the electrolyte spray range, a nanocrystalline metal layer is deposited on the worn areas, achieving a synergistic repair. For copper nuts on ordinary machine tools, if the housing is made of cast iron, the press-fit copper nut liner can be directly replaced. This modular design reduces maintenance complexity.
