**Analysis of Testing Skills for Bearing and Shaft Cooperation**
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*This article was published on China Bearing Network on January 1, 2013.*
When it comes to the cooperation between bearings and shafts, ensuring proper clearance is essential. This is crucial for smooth operation and longevity of the mechanical system. There are several methods used to test the radial clearance between a bearing and its shaft.
One common method is the **ruler detection method**, which is suitable for bearings with larger diameters. In such cases, a narrow feeler gauge can be directly used to measure the gap. However, for smaller diameter bearings where the clearance is very tight, this method may not be accurate enough. In these situations, other techniques like the **lead wire method** are preferred.
The **lead wire method** is more precise than the feeler gauge but requires more steps. A soft lead wire is used, with a diameter approximately 1.5 to 2 times the expected clearance. The wire is cut into sections of 15–40 mm in length and placed on the journal as well as the upper and lower parts of the bearing. After securing the bearing cover and tightening the bolts to the specified torque, the bolts are loosened, and the cover is removed. The flattened lead wire is then measured using a micrometer to determine the average top clearance of the bearing.
If the clearance is too small, the bearing may need to be adjusted by reducing the thickness of the pad or scraping the bearing surface. If the clearance is too large, additional shims or re-casting of the bearing surface might be required.
Another important aspect is the **adjustment of bearing bushing force**. To prevent axial movement or misalignment during operation, the bearing cap should compress the bushing. This is done similarly to the top clearance measurement, where the thickness of the compressed lead wire is measured. This helps calculate the elastic deformation of the bushing after tightening, which indicates the pressing force applied.
Typically, the bearing bushing force should range between 0.02 and 0.04 mm. If this value does not meet specifications, the thickness of the gasket at the joint between the bearing and housing can be adjusted accordingly. It's important to note that padding the back of the bearing tile is not allowed.
In addition to radial clearance, **axial clearance** must also be considered. Axial clearance can be checked by moving the shaft to one end and measuring the distance between the two ends using a feeler gauge or a dial indicator. This gives an accurate reading of the axial play.
When the sliding bearing clearance does not meet the required standards, adjustments must be made. For split bearings, radial clearance (top clearance) is usually adjusted using shims or by modifying the bearing surface.
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