How to repair crankshaft wear and tear

The wear of the crankshaft journal is a common fault in engines, often caused by poor lubrication, impurities, etc. If the wear exceeds the standard, it can cause engine noise, low oil pressure, and other problems. The crankshaft repair needs to choose an appropriate solution based on the degree of wear and location, taking into account both repair accuracy and reliability. The following are the mainstream repair methods and applicable scenarios.

1、 Neck grinding repair method: mainstream conventional repair scheme

Journal grinding is the core method for handling slight to moderate wear of crankshafts, suitable for situations where the journal surface has only uniform wear, no cracks, and severe pull marks. During repair, the crankshaft is clamped onto a specialized crankshaft grinder. Based on the actual wear amount, the main journal and connecting rod journal are precisely ground according to the original factory standard repair dimensions to remove the wear layer and restore the roundness and cylindricity of the journal, while ensuring the smoothness of the journal surface. After grinding and repairing, it is necessary to select the corresponding repair size of the bearing shell, so that the fit clearance between the journal and the bearing shell meets the original factory requirements. This method has mature technology, high repair accuracy, and can fully restore the performance of the crankshaft. It is the preferred solution for repair shops.

2、 Electroplating repair method: suitable for repairing minor wear and tear

Electroplating repair mainly involves chrome plating or iron plating processes, which are suitable for situations where the shaft neck is slightly worn and does not require significant cutting. When repairing, first polish and clean the surface of the journal, and then deposit a layer of metal coating on the worn surface through electroplating technology. The thickness of the coating is determined according to the amount of wear. After electroplating, precision grinding is carried out to restore the journal size to standard. This method can preserve the original dimensions of the crankshaft without the need to replace non-standard bearing shells. It has relatively low equipment requirements, but the bonding strength between the coating and the substrate is limited, making it unsuitable for crankshafts with severe wear or high load conditions. In addition, the electroplating process requires anti-corrosion treatment to avoid coating detachment.

3、 Welding repair method: for severe wear or local damage

Welding repair is suitable for situations where the crankshaft journal has severe wear, deep tensile marks, or local metal loss. Common methods include manual arc welding, gas shielded welding, etc. When repairing, the worn parts should be pre treated to remove fatigue layers and impurities, and then special welding materials should be used for surfacing to restore the shaft neck to its original size or repair size. After surfacing, annealing treatment should be carried out to eliminate welding stress, and then grinding and finishing should be carried out. This method has high repair strength and can deal with serious damage, but it requires extremely high welding technology. If the temperature control during welding is improper, it can easily cause crankshaft deformation and crack formation. It is only suitable for professional manufacturers to repair.

The core of crankshaft repair is to choose the right method based on the degree of wear. Minor wear can be repaired by electroplating or small-sized grinding, while moderate to severe wear should be repaired by grinding or welding after grinding. Regardless of the solution, strict inspection of the dimensional tolerances and fit clearances of the shaft neck is required after repair, and the repaired crankshaft must be adequately lubricated before installation to avoid the recurrence of wear and tear faults.