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What Is Clearance And How Is Clearance Measured For Rolling Bearings

The clearance of a rolling bearing is the maximum amount of activity that holds one ring in place and the other in radial or axial direction. The maximum activity along the radial direction is called radial clearance, and the maximum activity along 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, clearance can be divided into the following three types:

I. Original clearance

Free clearance before bearing installation. The original clearance is determined by the manufacturer's processing and assembly.

2. Install the clearance 

Also known as fit clearance, it is the clearance when the bearing and shaft and bearing housing have been installed but not yet working. The mounting clearance is smaller than the original clearance due to interference mounting, either increasing the inner ring, reducing the outer ring, or both.

3. Work clearance

When the bearing is in working condition, the inner ring temperature rises to the maximum and the thermal expansion to the maximum, so that the bearing clearance decreases. At the same time, due to the effect of load, elastic deformation occurs at the contact point between the rolling body and the raceway, which increases the bearing clearance. Whether the bearing working clearance is larger or smaller than the mounting clearance depends on the combined effect of these two factors.

Some rolling bearings cannot be adjusted or disassembled. They are available in six models, from 0000 to 5000; There are type 6000 (angular contact bearings) and type 1000, Type 2000 and Type 3000 with cone holes in the inner ring. The mounting clearance of these types of rolling bearings, after adjustment, will be smaller than the original clearance. In addition, some bearings can be removed, and the clearance can be adjusted. There are three kinds of bearings: Type 7000 (tapered roller bearing), type 8000 (thrust ball bearing) and type 9000 (thrust roller bearing). There is no original clearance in these three kinds of bearings. For type 6000 and type 7000 rolling bearings, the radial clearance is reduced and the axial clearance is also reduced, and vice versa, while for type 8000 and type 9000 rolling bearings, only the axial clearance is of practical significance.

Proper mounting clearance facilitates the normal operation of the rolling bearing. The clearance is too small, the rolling bearing temperature rises, unable to work normally, so that the rolling body gets stuck; Excessive clearance, equipment vibration, rolling bearing noise.

The radial clearance inspection method is as follows:

I. Sensory method

1. With hand rotating bearing, the bearing should be smooth and flexible without sticking and astringency.

2. Shake the outer ring of the bearing by hand. Even if the radial clearance is only 0.01mm, the axial movement of the top point of the bearing is 0.10-0.15mm. This method is used for single row centripetal ball bearings.

Measurement method 

1. Check and confirm the maximum load position of the rolling bearing with a feeler, insert a feeler between the rolling body 180° and the outer (inner) ring, and the appropriate thickness of the feeler is the radial clearance of the bearing. This method is widely used in self-aligning bearings and cylindrical roller bearings.

2, check with the dial indicator, first set the dial indicator to zero, then lift the rolling bearing outer ring, the dial indicator reading is the radial clearance of the bearing.

The inspection method of axial clearance is as follows:

1. Sensory method

Check the axial clearance of the rolling bearing with your finger. This method should be used when the shaft end is exposed. When the shaft end is closed or cannot be checked by fingers for other reasons, check whether the shaft is flexible in rotation.

2. Measurement method

(1) Check with feeler. The operation method is the same as that of checking radial clearance with feeler, but the axial clearance should be

C = lambda/sin (2 beta)

Where c -- axial clearance, mm;

-- Gauge thickness, mm;

-- Bearing cone Angle, (°).

(2) Check with the dial indicator. When the crowbar is used to channel the moving shaft to two extreme positions, the difference of dial indicator reading is the axial clearance of the bearing. However, the force applied to the crowbar should not be too large, otherwise the shell will have elastic deformation, even if the deformation is very small, it will affect the accuracy of the measured axial clearance.

Media Contact
Company Name: Hxh Bearing Co., Limited
Contact Person: Hxh Bearing
Email: Send Email
Phone: 18168912858
Address:No.311 Guangnan Road, Liangxi District
City: Wuxi
State: Jiangsu
Country: China

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