Analysis of Bearing Clearance and Application of Matching Instruments

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Improving the bearing clearance rate is a crucial aspect of ensuring the quality and performance of bearings. One of the key indicators in bearing matching is the radial clearance, which refers to the total gap between the inner and outer raceways and the rolling elements in the diameter direction. This clearance plays a vital role in determining whether a bearing meets the required specifications and is essential for its proper operation. If the clearance value does not meet the technical standards, it can negatively affect the load distribution, rotation accuracy, vibration levels, and overall lifespan of the bearing. Therefore, maintaining and improving the clearance rate is essential for achieving reliable and long-lasting bearing performance. In the process of manufacturing bearings, if the radial clearance pass rate is low, it's important to identify the root cause quickly. A causal analysis approach helps uncover the main factors affecting the quality of the bearing clearance. These factors typically include testing instruments, process methods, and operator skills. Traditionally, the method of matching inner and outer rings with steel balls involved measuring the diameter errors using an instrument, calculating the inner and outer groove diameters based on the gauge clearance, and selecting the appropriate scale. However, this approach often led to inconsistencies due to variations in measurement techniques and the curvature of the grooves. As a result, the radial clearance qualification rate was unstable, leading to frequent rework and difficulty in maintaining consistent product quality. To address these issues, the use of specialized matching instruments has proven effective. By ensuring the accuracy of both the processing of bearing parts and the testing instruments, these tools allow for more precise and consistent radial clearance measurements. The principle behind the matching instrument involves ensuring that the bearing clearance adheres to standard rules. The formula for radial clearance error in a ball bearing is: **U = XY - 2Z** or **XY = U + 2Z** Where: - **U** = Radial clearance of the bearing without load - **X** = Outer groove diameter error - **Y** = Inner groove diameter error - **Z** = Steel ball diameter error The U value can be referenced from national standards, while the Z value is usually marked on the steel ball. The matching instrument is used to measure the X and Y values simultaneously, select the appropriate steel ball, and then check the radial clearance using a radial clearance meter. The calibration process of the matching instrument involves aligning the inner and outer groove diameter specifications. Since the instrument uses a two-point comparison method, it requires two calibration standards: one for the inner ring and one for the outer ring. The instrument is equipped with three dial gauges—two for the inner and outer groove diameter errors, and one for the (XY) value at the same time. For example, if the actual diameter error of the outer ring groove is +8 µm, and the inner ring groove is -5 µm, then **XY = +8 - (-5) = 13 µm**. When calibrating, the central dial gauge should point to +13 µm. If it doesn't, the instrument needs to be adjusted accordingly. Once the inner and outer groove diameter scales are properly sorted, the left and right dial gauges can be omitted, and only the central dial gauge is used to reflect the (XY) value and select the appropriate steel ball. This ensures that the radial clearance meets high specification requirements. It's important to emphasize that during the matching process, standard parts should always be used to calibrate the instrument. Avoiding shortcuts ensures accurate (XY) measurements, which directly impacts the correct calculation of the bearing clearance. With proper use of matching instruments, the qualified rate can reach up to 98–100%.

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Recommended Reading: - Characteristics of LYC Universal Joint Bearings - Tapping Techniques in SKF Bearings - Common Knowledge and Technology of Imported Bearings - Features and Applications of Plastic Bearings - How to Extend the Life of Rolling Mill Bearings This article is linked to http:// Please reference China Bearing Network http:// Previous: Precautions for Ensuring Normal Operation of Spindle Bearings Next: Common Causes of Failure in NSK Imported Bearings and Application Notes

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