Bearing Clearance: Definition and Grouping Explained

Bearing Clearance Definition and Grouping Explained

Clearance is a critical concept in bearings, central to the process of bearing selection and maintenance. Therefore, it is essential to elaborate on the concept of rolling bearing clearance, standard limits, selection principles, and corresponding calculations.

Understanding the Concept of Bearing Clearance

Bearing clearance has a clear definition. For rolling bearings, it generally refers to the relative movement distance between one fixed ring and another. It can be understood as the gap between the inner and outer rings of the bearing.

In the case of cylindrical roller bearings, due to the existence of bearing clearance, the inner and outer rings of the bearing can achieve a certain distance of relative movement in the radial direction.

This distance is the radial clearance of the cylindrical roller bearing. For NU and N series cylindrical roller bearings, due to their structure, these two types of bearings can achieve axial displacement.

There is no limit to the axial movement between the inner and outer rings of the bearing structure itself, so these bearings do not have the concept of axial clearance.

For cylindrical roller bearings with flanges like the NJ series, the inner and outer rings of the bearing can move relative to each other axially. This movement is restricted by the internal structure of the bearing, but this amount is generally the axial movement that can be achieved internally by the bearing, which is not included in the clearance.

For deep groove ball bearings, the bearing raceway is an arc groove, so the axial movement of the bearing is restricted by the groove structure. The axial relative movement distance of the inner ring relative to the outer ring is the axial clearance of the bearing; the radial relative movement distance between the inner and outer rings of the bearing is the radial clearance of the bearing.

In general bearing catalogs, under default conditions, the clearance of the following bearings refers to radial clearance:

  • Deep Groove Ball Bearings
  • Cylindrical Roller Bearings
  • Self-Aligning Roller Bearings
  • Needle Bearings
  • Self-Aligning Ball Bearings

Under default conditions, the clearance of the following bearings refers to axial clearance:

  • Angular Contact Ball Bearings
  • Tapered Roller Bearings

Bearing Clearance Grouping and Limit Values

There are national standards for bearing clearances. Newly manufactured bearings follow these standards. The Chinese National Standard GB/T4604 provides the standard limit values for radial clearance in rolling bearings.

According to these standards, the clearance of rolling bearings in China are roughly divided into five groups: Group 2 (C2), Standard Group (C0), Group 3 (C3), Group 4 (C4), and Group 5 (C5).

The Standard Group, also represented by some brands as CN, is the standard clearance. Group 2 has less clearance than the Standard Group, Group 3 has more clearance than the Standard Group, and Group 4 has more clearance than Group 3.

In the application of general motors and gearboxes, the most commonly used clearances are the Standard Clearance and Group C3. Further details on the principles and methods of specific selection will be described later.

In addition to the standard clearance grouping, in the field of motor applications, there is also something called CM clearance. CM stands for Clearance for Motor. Overall, CM clearance falls within the range of Standard (CN) clearance, but its average value is less than that of CN. It represents a narrower segment within the Standard (CN) clearance, situated toward the lower end.

It’s not hard to understand that CM clearance is a subset of CN clearance, but its range is narrower and its average value is smaller than that of CN.

Therefore, it can be considered a type of clearance where the control precision is improved and the overall clearance is reduced. Subsequent sections on bearing clearance and bearing performance will explain how such a choice of clearance benefits the noise performance of the bearing, which is why it’s chosen for application in motors.

The clearances of commonly used deep groove ball bearings are shown in the following table:

Table 1: Deep Groove Ball Shaft μm
Nominal Inner Diameter
d/mm
Group 2Group 0Group 3Group 4Group 5
ExceededTominmaxminmaxminmaxminmaxminmax
2. 56072139023
61007213802314292037
1018010318112518332545
1824011520132820362848
2430111520132823413053
3040111620153328464064
4050115623183630514573
5065115828234338615590
658011810302551467165105
8010022012363058538475120
10012022315413666619790140
120140071848418171114105160
1401602231853469181130120180
16018022520615310291147135200
180200230257163117107163150230

The clearance for commonly used cylindrical roller bearings is shown in the table below:

Table 4: Cylindrical Hole Cylindrical Roller Bearing μm
Nominal Inner Diameter
d/mm
Group 2Group 0Group 3Group 4Group 5
ExceededTominmaxminmaxminmaxminmaxminmax
 10025204535605075
10240252045356050756590
24300252045356050757095
304053025504570608580105
4050535306050807010095125
506510404070609080110110140
6580104540756510090125130165
801001550508575110105140155190
1001201555509085125125165180220
120140156060105100145145190200245
140160207070120115165165215225275
160180257575125120170170220250300
180200359090145140195195250275330
20022545105105165160220220280305365
22525045110110175170235235300330395
25028055125125195190260260330370440
28031555130130205200275275350410485
31535565145145225225305305385455535
355400100190190280280370370460510600
400450110210210.310310410410510565665
450500110220220330330440440550625735
Don't forget, sharing is caring! : )
Shane
Author

Shane

Founder of MachineMFG

As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.

Up Next

Mastering CAD/CAM: Essential Technologies Explained

Basic Concepts of Computer-Aided Design and Computer-Aided Manufacturing Computer-aided design and computer-aided manufacturing (CAD/CAM) is a comprehensive and technically complex system engineering discipline that incorporates diverse fields such as computer [...]

Virtual Manufacturing Explained: Concepts & Principles

Concept of Virtual Manufacturing Virtual Manufacturing (VM) is the fundamental realization of the actual manufacturing process on a computer. It utilizes computer simulation and virtual reality technologies, supported by high-performance [...]

Understanding Flexible Manufacturing Systems: A Guide

A Flexible Manufacturing System (FMS) typically employs principles of systems engineering and group technology. It connects Computer Numerical Control (CNC) machine tools (processing centers), coordinate measuring machines, material transport systems, [...]

Exploring 4 Cutting-Edge Nanofabrication Techniques

Just as manufacturing technology plays a crucial role in various fields today, nanofabrication technology holds a key position in the realms of nanotechnology. Nanofabrication technology encompasses numerous methods including mechanical [...]

Ultra-Precision Machining: Types and Techniques

Ultra-precision machining refers to precision manufacturing processes that achieve extremely high levels of accuracy and surface quality. Its definition is relative, changing with technological advancements. Currently, this technique can achieve [...]

Exploring High-Speed Cutting: Tech Overview & Application

Cutting machining remains the most prominent method of mechanical processing, holding a significant role in mechanical manufacturing. With the advancement of manufacturing technology, cutting machining technology underwent substantial progress towards [...]

Top 7 New Engineering Materials: What You Need to Know

Advanced materials refer to those recently researched or under development that possess exceptional performance and special functionalities. These materials are of paramount significance to the advancement of science and technology, [...]

Metal Expansion Methods: A Comprehensive Guide

Bulge forming is suitable for various types of blanks, such as deep-drawn cups, cut tubes, and rolled conical weldments. Classification by bulge forming medium Bulge forming methods can be categorized [...]
MachineMFG
Take your business to the next level
Subscribe to our newsletter
The latest news, articles, and resources, sent to your inbox weekly.
© 2024. All rights reserved.

Contact Us

You will get our reply within 24 hours.