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What is the clearance and how to measure the clearance of rolling bearings?

by:JNSN     2021-12-29
The so-called clearance of a rolling bearing is the maximum amount of movement in the radial or axial direction of one ferrule while the other ferrule is fixed. The maximum amount of movement in the radial direction is called radial clearance, and the maximum amount of movement in the axial direction is called axial clearance. Generally speaking, the larger the radial clearance, the larger the axial clearance, and vice versa. According to the state of the bearing, the clearance can be divided into the following three types:    one, the original clearance    the clearance when the bearing is installed in the free state. The original clearance is determined by the processing and assembly of the manufacturer.  Second, installation clearance    is also called the fit clearance, which is the clearance when the bearing and the shaft and the bearing seat are installed but not yet working. Due to the interference installation, either the inner ring is enlarged, or the outer ring is reduced, or both, the installation clearance is smaller than the original clearance. 3. Working clearance The clearance of the bearing in the working state, the maximum temperature rise of the inner ring and the largest thermal expansion during operation, reduce the bearing clearance; at the same time, due to the load, the contact between the rolling element and the raceway produces elastic deformation. Increase the bearing clearance. Whether the bearing working clearance is larger or smaller than the installation clearance depends on the combined effect of these two factors. Some rolling bearings cannot be adjusted in clearance, let alone dismantled. These bearings have six models, namely 0000 to 5000; some rolling bearings can be adjusted in clearance but cannot be dismantled. There are 6000 type (angular contact bearings) and tapered bore in the inner ring. 1000 type, 2000 type and 3000 type rolling bearings, the installation clearance of these types of rolling bearings will be smaller than the original clearance after adjustment; in addition, some bearings can be disassembled and the clearance can be adjusted. Type 7000 (tapered roller bearings) ), 8000 type (thrust ball bearing) and 9000 type (thrust roller bearing), these three types of bearings do not have the original clearance; 6000 type and 7000 type rolling bearings, the radial clearance is adjusted, the axial clearance It also becomes smaller, and vice versa. For the 8000 and 9000 rolling bearings, only the axial clearance is of practical significance.  Proper installation clearance contributes to the normal operation of rolling bearings. If the clearance is too small, the temperature of the rolling bearing will rise, and it will not work normally, and the rolling elements will be stuck; if the clearance is too large, the equipment will vibrate and the rolling bearing will be noisy.  The inspection method of radial clearance is as follows:   1. Feeling method  1. If the bearing is rotated by hand, the bearing should be stable and flexible without jamming.  2. Shake the outer ring of the bearing by hand, even if the radial clearance is only 0.01mm, the axial movement of the uppermost point of the bearing is 0.10~0.15mm. This method is dedicated to single-row radial ball bearings. 2. Measurement method 1. Check with a feeler gauge to confirm the maximum load position of the rolling bearing. Insert a feeler gauge between the rolling element and the outer (inner) ring which is 18 with it. The thickness of the feeler gauge with suitable elasticity is the radial clearance of the bearing. . This method is widely used in self-aligning bearings and cylindrical roller bearings.  2. Check with a dial gauge, first adjust the dial gauge to zero, and then jack up the outer ring of the rolling bearing. The reading of the dial gauge is the radial clearance of the bearing.  The method of checking the axial clearance is as follows:   1, sensory method  Check the axial clearance of the rolling bearing with your fingers. This method is applied to the occasion where the shaft end is exposed. When the shaft end is closed or cannot be checked with your fingers for other reasons, you can check whether the shaft rotates flexibly. 2. Measurement method (1) Use feeler gauge to check, the operation method is the same as that of feeler gauge to check radial clearance, but the axial clearance should be cu003dλ/(2sinβ)   where c—— axial clearance , Mm;   λ——thickness of feeler gauge, mm;   β——bearing cone angle, (°).   (2) Check with a dial gauge, and use a crowbar to move the shaft so that the shaft is in two extreme positions. The difference between the dial gauge readings is the axial clearance of the bearing. However, the force applied to the crowbar cannot be too large, otherwise the shell will be elastically deformed, even if the deformation is small, it will affect the accuracy of the measured axial clearance.
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