What Are Our Concerns About Bearings（43）

Q1:What is thrust roller bearing?

A:Thrust roller bearings are used to bear combined axial and radial loads mainly in axial direction, but the radial load shall not exceed 55% of the axial load.  Compared with other thrust roller bearings, this kind of bearing has lower friction coefficient, higher speed and self-aligning performance. 

 The rod of type 29000 bearing is asymmetric spherical roller, which can reduce the relative sliding of roller and raceway at work. Moreover, the roller is long and large in diameter, the number of rollers is large, and the load capacity is high. Oil lubrication is usually used, and grease lubrication can be used in some cases of low speed.  In the design selection, should be preferred;  

80000 type thrust cylindrical roller bearing, 90000 type thrust tapered roller bearing and AXK type thrust needle roller bearing can withstand unidirectional axial load, which is much larger than the axial load capacity of thrust ball bearing, and large rigidity, occupy small axial space.  

Thrust cylindrical roller bearing and thrust needle roller bearing are suitable for the occasion of low speed, the speed of thrust tapered roller bearing is slightly higher than that of thrust cylindrical roller bearing.  

Thrust roller bearings are divided into thrust cylindrical roller bearings, thrust self-alting roller bearings, thrust tapered roller bearings, thrust needle roller bearings.  Thrust cylindrical roller bearings are mainly used in oil drilling RIGS, iron and steel machinery.  This type of thrust self-aligning roller bearing is mainly used in: hydraulic generator, vertical motor, ship propeller shaft, tower crane, extruder and so on. 

 Thrust tapered roller bearing this kind of bearing main uses: one-way: crane hook, oil drilling ring.  Two-way: roll neck of rolling mill.  Planar thrust bearing is mainly subjected to axial load in assembly and is widely used.  

Although the installation and operation of thrust bearings are relatively simple, errors often occur in actual maintenance, that is, the installation position of the tight ring and loose ring of the bearings is not correct, which results in the loss of the bearing and the journal is quickly worn out.  The tight ring is installed on the end face of the stationary part, that is, wrong assembly.  The inner ring of the tight ring is a transition fit with the shaft journal. When the shaft rotates, the tight ring is driven and friction occurs with the end face of the stationary part. When the axial force (Fx) is applied, the friction torque is greater than the resistance moment of the inner diameter fit, resulting in forced rotation of the tight ring and the shaft mating surface, which intensifies the wear of the shaft journal.  

Q2：How to identify the bearing type?

A:Imported bearings and domestic bearings are divided into nine categories;  

• ★ Class 0 — Deep groove ball bearings 604-699, 6000-6044, 6200-6240, 6300-6334, 6403-6418, 6800-6844, 69-6930, 16001-16032  
• ★ Class 1 — Self-aligning ball bearings 1200-1222, 1300-1322, 2200-2222, 2300-2322  
• ★ Class 2- Cylindrical roller bearings N203-NF309, NJ203-NJ330, NJ2204-NJ2328, NU202-NU1408,NU2205-NU2338,NUP207-NN3060  
• ★ Class 3 — Self-aligning roller bearings 21304-22226, 22228-22348, 22348-23072, 23120-2317223218-24152  
• Class 6 – Angular contact ball bearings 5200-5315,7000-7240,7244-7410  
• ★ Class 7 – Tapered roller shafts 30202-32330,E30202-E32319,HR30202-HR32009,HR32010-HR33216  
• ★ Class 8 – Thrust ball bearings 23917-29434,51100-51244,51304-51420  
• ★ Class 9 – Thrust roller bearings AXK1024-AXK120155, 81102-89320ZW, 29322-29444 89448-91754  
• ★ External spherical bearings UC201-UC313,UCF203-UCT206,UK205-UKP213  
• ★ Needle roller bearings RNA4900-TA5520,SDM6Y-307641,TLA1010Z-SDE40Y  
• ★ Ball screw bearings, stainless steel bearings, oil bearing, linear bearing, bearing seat  

Q3:What is the rated axial load of double row tapered roller bearing 352008?

A:Tapered roller bearings belong to separation bearings, bearing inner and outer rings have conical row raceway.  According to the number of roller rows, the bearings can be divided into single row, variable row and four row tapered roller bearings.  Single row tapered roller bearings can withstand radial load and single direction axial load.  When the bearing bears radial load, there will be an axial component, so when another bearing that can withstand the axial force in the opposite direction is needed to balance it.  

The capacity of single-row tapered roller bearings to bear axial load depends on the contact Angle, that is, the outer raceway Angle, the greater the Angle, the greater the axial load capacity.  Tapered roller bearings in the amount of single row tapered roller bearings.  Small size double row tapered roller bearings are used in front wheel hub of car.  Four row tapered roller bearings are used in heavy machines such as large cold rolling mill and hot rolling mill.  

Q4:What is the method of representation of bearing type?

A:1. Bearing type representation: Code (fourth digit from right)

• 0: deep groove ball bearing  
• 1: self-aligning ball bearing  
• 2: cylindrical roller bearings  
• 3: self-aligning roller bearing  
• 4: needle roller bearings  
• 5: spiral roller bearings  
• 6: Angular contact ball bearing  
• 7: tapered roller bearings  
• 8: thrust ball bearing thrust angular contact ball bearing  
• 9: thrust cylindrical roller bearing thrust self-aligning roller bearing thrust needle roller bearing thrust tapered roller bearing  

2.  Bearing dimension representation  

Diameter series, code (third digit from right)  

Ultra light: 7 cases: 1000700  

Ultra light: 8 and 9 cases: 7000800 7000900  

Extra light: 1 7 cases: 7000100 7002700  

Light: 2 cases: 3056200  

Chinese: 3 cases: 300  

Weight: 4 cases: 2086400  

Width series, code (seventh digit from right)  

Narrow: 7 cases: 7000800  

Normal: 1 case: 1000700  

Width: 2 cases: 2007900  

Extra-wide: 3 cases: 3000700  

Example: 4774900  

Height series, code (seventh digit from right)  

Extremely low: 7 cases: 7589900  

Low: 9 cases: 9008900  

Normal: 1 example: 1008900  

3, bearing inner diameter representation  

Bearing standard inner diameter: 10  

01 Inner diameter: 12  

02 INSIDE diameter: 15  

03 Inner diameter: 17  

Number *5= Inner diameter Example: 205: Inner diameter 25, 206, 30  

Bearing code is read as:  

Lead code: Bearing clearance, bearing tolerance class  

Code number right number:  

7: Width series  

6.  5: Bearing structure form  

Type 4:  

3: Diameter series  

2,1: bearing inner diameter  

Example: 3G3053220, that is, radial clearance according to the third group, class G tolerance, tolerance grade according to the letters B, C, D, E, G, in order from high to low tolerance grade.  Class G is generally omitted in the bearing code  

Imported bearing precode indicates the brand, 6203,6 means thrust angular contact ball bearing, 2 means light series, 03 means bearing inner diameter, 03 inner diameter is 17  

6305,6 means thrust angular contact ball bearing, 3 means medium series, 05 means inner diameter, 5 times 5, inner diameter is 25.