Bearing Selection Guide
The types, structures, and sizes of rolling bearings are diverse. In order to make the mechanical device play the expected performance, it is very important to choose the most suitable bearing.
To select a bearing, many factors need to be analyzed. The general sequence is as follows:
(1) Understand the operating conditions of mechanical devices and bearings, etc.
(2) Clear requirements for bearings
(3) Select the type of bearing
(4) Select the bearing configuration
(5) Select bearing size
(6) Select bearing specifications
(7) Installation method of selected bearing
The location of the bearing, the operating conditions, and the environmental conditions are the prerequisites for choosing a suitable bearing. For this, it is necessary to obtain the following data and information:
(1) Function and structure of the mechanical device
(2) Where to use the bearing
(3) Bearing load (size, direction)
(4) Rotation speed
(5) Vibration and shock
(6) Bearing temperature (ambient temperature, temperature rise)
(7) Ambient atmosphere (corrosive, clean, lubricating)
How to select the bearing type for your machine?
When selecting a bearing type, it is important to fully understand the operating conditions of the bearing. The following table lists the main analysis items:
| Analysis Items | Selection Method | |
| 1) Bearing installation space | Bearings that can be accommodated in the bearing installation space. |
As the shaft is designed with an emphasis on the rigidity and strength of the shaft, the shaft diameter is the inner diameter of the bearing, which is generally determined first. However, rolling bearings have a variety of size series and types, from which we should select the most suitable bearing type. |
| 2) Load | The following factors need to be considered:
The size of the load; Radial load, axial load; from one direction or two-direction; The degree of vibration or shock. |
Generally speaking, the radial load capacity of bearings with the same inner diameter increases in the following order: deep groove ball bearings |
| 3) Rotation Speed | The limit speed of the bearing is not only taken from the bearing type but also limited to the bearing size, cage type, accuracy grade, load condition, and lubrication method, etc. Therefore, these factors must be considered when selecting. |
The following bearings are mostly used for high-speed rotation: Deep groove ball bearings, |
| 4) Rotation Accuracy | For machine tool spindles that require high runout accuracy, as well as machinery that requires high speeds such as turbochargers, high-precision bearings in Grade 5, Grade 4, and Grade 2 should be used. | The following bearings are generally used in high accuracy applications:
Deep groove ball bearings, |
| 5) Rigidity | When the bearing is under load, the contact part between the rolling elements and the raceway will be elastically deformed. "High rigidity" means that the amount of deformation of this elastic deformation is small. | In parts such as the main shaft of the machine tool and the final reduction gear of the automobile, while increasing the rigidity of the shaft, the rigidity of the bearing must also be improved.
Roller bearings are less deformed under load than ball bearings. Preload the bearing (negative clearance) can increase rigidity. This method is suitable for angular contact ball bearings and tapered roller bearings. |
| 6) Relative inclination of the inner ring and outer ring | If the relative tilt between the inner ring and the outer ring is too large, the bearing will be damaged due to internal load. Therefore, we should select a bearing type that can withstand this tilt. | The allowable tilt angle (or self-align angle) increases in the following order: |
| 7) Assembly and disassembly | Frequency and method of assembly and disassembly for regular inspection | When assembly and disassembly are frequent, it is more convenient to use cylindrical roller bearings with separable inner and outer rings, needle roller bearings, and tapered roller bearings.
Tapered bore spherical ball bearing and spherical roller bearings can be easily assembled and disassembled through the use of fasteners or withdrawal sleeves. |
How to select the correct bearing configuration for your machine?
The type of machinery is different, the service conditions of the bearings will be different, and the performance requirements are also different. Generally speaking, there are more than two bearings that would be used on a shaft.
In order to facilitate axial positioning, most of the bearings are used as fixed-end bearings, and the rest are used as floating-end bearings. The following table lists the choice of fixed end and floating end bearing structure.
| Analysis | Applicable bearing type | |
| Fixed-end Bearing |
Bearings used for axial positioning and fixing: Select bearings that can bear radial and axial loads at the same time. In order to bear the bidirectional axial load, it is necessary to consider the corresponding strength according to the axial load during installation. |
Deep groove ball bearings, Match pair angular contact ball bearings, Double row angular contact ball bearing, Self-aligning ball bearing, Cylindrical roller bearings with ribs, Double row tapered roller bearing,
|
| Floating-end Bearing |
Used to avoid the expansion and contraction of the shaft caused by temperature changes during operation, and to adjust the axial position of the bearing. It is advisable to select a bearing that only bears the radial load and the inner ring and outer ring can be separated. When using non-separable bearings, a clearance fit is generally adopted between the outer ring and the housing, so that when the shaft expands and contracts with heat, the bearing can be used for axial avoidance.
|
Separate type:
Non-separable type: Deep groove ball bearing, Combined angular contact ball bearing (back to back combination), Double row angular contact ball bearings, Self-aligning ball bearing, |
| When the shaft does not distinguish between the fixed-end and Floating-end. | When the bearing spacing is small and the effect of shaft expansion and contraction is not large, two angular contact ball bearings or tapered roller bearings that can withstand axial load are used in face to face or back to back configuration.
Adjust the axial clearance after installation with nuts or washers.
|
Deep groove ball bearing, Self-aligning ball bearing, (NJ type, NF type) |
| For vertical shaft | The fixed end uses bearings that can bear radial load and axial load at the same time. When the axial load is large, the thrust bearing and the radial bearing are used together.
Similarly, a bearing that can only bear the radial load is selected for the floating end to avoid expansion and contraction of the shaft. |
Fixed end Combined angular contact ball bearing (back to back) Double row tapered roller bearings Thrust bearing and radial bearing are used together
|
How to select bearing types according to different industrial applications?
1. Select bearings for Machine Tools:
CNC Pipe Threading Lathe
CNC Lathe Machine
CNC Milling Machine
CNC Turning Center
Grinding Machine
etc.
For the precision machine tool spindle bearings, the precision grade should be better than P5, better in Grade P4, Grade P2. The following bearing types are widely used in the machine tools industry:
1) Angular Contact Ball Bearings
Angular contact ball bearings are the conversion bearings of deep groove ball bearings. They are characterized by the high rotating speed, which can bear radial load and axial load at the same time and can also bear pure axial load. Its axial load capacity is determined by the contact angle, and increasing with the increase of contact angle.
Advantages of angular contact ball bearings:
1. Simple structure;
2. The rotating speed is relatively high;
3. The friction torque is relatively small;
4. It can bear radial and axial loads at the same time;
5. The same external dimension is larger than the dynamic and static load capacity of deep groove ball bearings;
6. High rotation accuracy and low noise.
2) NN cylindrical roller bearings:
The NN cylindrical roller bearing is one separable type bearing and easy to assemble and disassemble. The advantages of the double-row cylindrical roller bearings are high stiffness and high precision, so they are usually used as main shaft bearings of precision machine tools.
Tapered roller bearings can withstand the combined radial and axial loads based on the radial direction. The bearing capacity depends on the raceway angle of the outer ring, the larger the angle, the greater the bearing capacity.
4) Double-direction Thrust Ball Bearing:
Advantages:
high precision, good rigidity, sufficient lubrication, low-temperature rise, high speed and convenient disassembly.
They are widely used on spindles of machine tools. This bearing can bear the combined load of radial and axial load at the same time, and limit the axial displacement of the two sides of the shaft. It is often used in combination with double-row cylindrical roller bearings NN series.
2. Select bearings for
Rotating Units, Medical Equipment,
Measurement Instruments
The following bearing types are widely used in precision rotary tables and industrial robots:
High precision: Grade P5, P4, P2.
High rigidity: This series bearing has preloaded.
High load：capable withstand double-direction axial load, radial load, and tilting moment
Small size: thin section, space-saving for machine tools.
YRT rotary table bearing structure can bear double-direction axial load, radial load, and tilting moment.
APPLICATION:
high precision rotary table,
milling machine, index head,
hobbing machine
CNC machine tools.
3. Select bearings for Steel Industry, Rolling Mills
Bearings for rolling mills must withstand heavy loads and high-speed rotations as well as very severe operating environments. In various industries, they are used under severe conditions in every respect. Thus, the requirements for the bearing's material, structure, and accuracy are very strict. Tedin produces double-row tapered roller bearings, four-row tapered roller bearings, and four-row cylindrical roller bearings for hot strip mills and cold strip mills. For the Z-mill or Sendzimir mill, Tedin produces double row cylindrical roller bearings and three-row cylindrical roller bearings for backup rolls.
Tedin's advantages:
1. High Purity Material:
DAYE steel or BAOSHAN steel GCr15SiMn, GCr18Mo, 100CrMo7-4, or imported OVAKO steel;
2. High Accuracy:
For roll neck bearings for rolling mills: ISO Grade P5, P4;
For backup roll bearings for Z-mills: ISO Grade P4,
The interface height difference of all bearings on the same shaft ≤ 0.005mm.
The difference between the wall thickness of adjacent bearings ≤ 0.002mm.
3. Crowned inner ring, raceway & rollers: Tapered rollers of TRB: with logarithmic profile,
4. With a specially designed cage structure.
5. Consistency of roller profiles and sizes
The tapered rollers of the double row and four-row tapered roller bearings are manufactured to such close dimensional and geometrical tolerances that they are practically identical. This provides optimal load distribution, reduces noise and vibration, and enables preload to be set more accurately.
6. Improved fatigue life
7. Reduced noise vibration
8. Customized structures and dimensions available
Typical Case:
Sendzimir mill (Z-mill): 20 high cold rolling mills for steel strip.
Applied bearing types: NNCF3680181X (sealed type), NNCF2660168X (sealed type)
Rolling mills for steel types: alloy steel, stainless steel, beryllium copper, etc.
Sendzimir mill (Z-mill): 12 high cold rolling mills for steel strip.
Applied bearing types: NNCF43110205X (sealed type), NNCF3680171X (sealed type), NNCF3680224X (sealed type)
Rolling steel types：Carbon Steel,Nonoriented silicon steel,Oriented silicon steel, etc.
FAQ:
1) The correct assembly method of four-row cylindrical roller bearings for rolling mills.
2) How to determine the clearance of four-row cylindrical roller bearings for rolling mills?
3) What are the common overload forms of rolling mill bearings?
4) Strengthen the maintenance of rolling mill bearings to extend the effective service life.
4. Select Tapered Rollers forWind Turbine Main Bearings
Tedin produces large-size tapered rollers for wind turbine main bearings.
Tapered Rollers for Wind Turbine Bearings:
(rotor bearings, main shaft bearings of wind turbines)
Diameter: 50mm - 130mm;
Material: 100CrMo7-4, Case-hardened Steel G20Cr2Ni4A, OVAKO Steel, TIMKEN 3311 Steel, TIMKEN 4320 Steel;
Profile: Logarithmic Profile
Sorting Diameter Variation: 0.003 mm;
Surface super finished: Ra 0.2
Tapered Rollers φ 62 x 116mm
(Onshore)
Large end diameter: 62.32mm
Length: 116mm
Material: Case-hardened Steel
Hardness: HRC 58-62
Case-hardened Depth: ≥3mm
Profiling: Logarithmic Profile
Surface Roughness: Ra 0.2
Diameter Variation: 0.003mm
Used for 5 MW Wind Turbines
(Offshore)
Material: Case-hardened steel
Hardness: HRC 59-63
Effective Case-hardened depth: ≥3.5mm
Diameter Variation: 0.003mm;
Profile: Logarithmic Profile
Surface Roughness: Ra 0.2
FULL Test Reports we can offer for the large-size tapered rollers:
1. Material Certificate
2. Chemical composition inspection result
3. Grain size inspection result
4. Retained austenite content microstructure
5. Cleanliness
6. Surface and core Hardness
7. Case hardness depth
8. NDT inspection result(MT,UT)
9. Roller profile report
10. Roughness test report
11. Burning test report
12. Final test reports on Dimensions