What is bearing? What do the bearing symbols mean?

In this article we present the common types of bearings and common international symbols that we encounter in today's market.

1- What is the ammunition used for?

In the design of machines as well as in the manufacture of machines and equipment, in order to reduce the frictional force when the two parts move relative to each other, people design sliding bearings (also known as bearings) and bearings.

You current ammo has been standardized and pre-made, when using we just choose accordingly and use.

2. What should we pay attention to when choosing bearings?

  • Purpose use: we can choose bearings light, medium, heavy, type of bearings round, kneading bullets, ammunition chopsticks, needle bullets, taper bullets, forks...
  • Suitable for details when assembling such as  inner diameter,  outside diameter, thickness of bearing bearing…
  • Bearing cost: is also a factor when choosing bearings, so it is possible to replace different types of bearings to meet the requirements of use

3. Structure of the bearing ammunition

Includes: Outer ring; inner ring, roller and cage

4. How to know the bearing parameters when designing and using bearings?

Bearing symbols have 05 numbers and 02 letters, usually people write 4  numbers and 2 letters


  • Where ABCDE are numbers
  • XX is the letters

The last two numbers (DE) are the convention for the inner diameter of the bearing:

  • For holes of 20 mm or more, we take the last 2 numbers DE and multiply by 4: like a 6204 bearing, we have an inner diameter (hole) of 04 x 5 = 20 (mm).
  • For holes smaller than 20 mm, the symbol is as follows: 03 is 17mm; 02 is 15 mm; 01 is 12mm; 00 is 10mm
  • The outer diameter of the bearing we look up in the table.

The third number from the right (C) is the load-bearing level of the bullet: 

  • 8 or 9 super light load only;
  • 1 or 7 indicates very light loads;
  • 2 light load only;
  • 3 medium load only;
  • 4 only heavy loads;
  • 5 only very heavy loads;
  • 6 indicates average load like 3 but thicker;

According to different load, ball diameter and outside diameter are different

For example bearing 6204 is a light bearing

The 4th number from the right (B) is the bearing type 

  • 0: Bearing bearing 1 row
  • 1: Bearing bearing two-row bridge cage;
  • 2: Short cylindrical ball bearing;
  • 3; Ball bearings support 2 rows of spherical beds;
  • 4: Needle ball bearing or long cylindrical ball bearing
  • 5: Helical cylindrical ball bearing
  • 6: Bearingblocking support
  • 7: Taper ball bearing
  • 8: Thrust ball bearing
  • 9: Blocking drive

The 5th number from the left (A) has structural meaning, basically understood as follows:

  • 3: Single row short cylindrical ball, retaining ring without flange
  • 4: Same as number 3 but has a barrier
  • 5: There is a slot to install the locking ring locating in the outer barrier
  • 6: There is an oil stopper made of steel sheet
  • 8: There are 2 feathers steel plate oil stopper
  • 9: Bishort cylindrical chopsticks in a row

XX is the type of bearing cap:

Different manufacturers use different symbols:

The types of bearing caps are as follows:

  1. Iron lid:
  • SKF : 2Z
  • FAG : ZR,2ZR
  • NACHI : ZE,2ZE

2. Plastic cap:

*Plastic cap  contact type:

  • SKF : RS1 (RSH),2RS1 (2RSH) …..can work in temperature – 40° to +120°
  • RS2 (2RS2)     …..can work in temperature – 60° to +180°
  • FAG : RSR,2RSR                     NSK : DU,DDU
  • NTN : LU,LLU                           KOYO : RS,2RS,RD,2RD

* Non-contact type plastic cap : can work in temperature - 40° to +120°

  • SKF : RZ (RSL),2RZ(2RSL)           FAG : RSD(2RSD)
  • NTN : LB,LLB                                 NSK : V,VV
  • KOYO : RU,2RU                             NACHI : NKE,2NKE



THT bac dan


vong bi con




bi cau chan

4. How to maintain bearings to increase the life of bearings

  • Assembling axis concentricity, no radial deviation,
  • For gearbox bearings with oil, lubricate with oil through pump or impeller
  • For bearings outside the gearbox, there is a barrier ring, periodically grease the bearing 
  • Avoid water, sand, or dirty objects falling into the bearing

5. Use of bearings in the design of automatic doors – automatic gates

  • For motors, bearings are installed according to European standards, so the quality is tested to be good and durable.
  • For automatic doors: depending on the structure and number of doors, choose suitable bearings, avoid using market goods, mainly used bearings.