BEARING BRIEF
The technological development of mankind in mechanical matters begins with the invention of the wheel.
At the point reached today, there is usually a bearing in the hub of the wheel and everything that rotates. 
Therefore, bearing is the most used machine element in the world.


    NUMBERING SYSTEM IN BEARINGS
Bearings are produced by major companies in the world and the same type of bearings are put on the market with a standard numbering system. 
This systematic has been standardized and published by ISO. Even in countries that do not use the metric system, these standard notations are followed.

The size systematic standardized by ISO was carried out simply as follows.

• The last two digits of the notation (far right)  used to indicate the inside diameter.  (See 3.1 inside diameter notation)

• The number to the left of the inside diameter designation (third from the right) is used to indicate the outside diameter. 
  In this digit, the smallest outer diameter with the same inner diameter size is indicated by 8, and the digit in the digit changes as 8, 9, 0, 1, 2, 3, 4 as the outer diameter increases.

• The number to the left of the outside diameter designation (fourth from the right) is used to indicate the bearing width. The number 0 is used for the narrowest bearing width with the same inside diameter. As the bearing width increases, this figure becomes 0, 1,  It is denoted as 2, 3, 4, 5. 
  (For thrust bearings, these numbers range from thin to thick as 7, 9, 1.)

• The letter or numbers at the beginning (leftmost) of the bearing designation indicate the bearing type. (See 3.2 Bearing type designation)

• After a space is left to the right of the two numbers on the right reserved for the inner diameter in the bearing notation, the special shapes of that bearing are indicated with various numbers or letters. (See 3.3 bearing special shape notations
  
  BEARING INSIDE DIAMETER

• There is a very simple rule about bearing inside diameter.
  For bore diameters greater than 19 mm and less than 496 mm, 5 times the last two digits in the bearing designation gives the bearing bore.
  Example: NU 1088 cylindrical bearing inner diameter d= 88*5= 440 mm.

• Since the last two digits in the display can be the largest 99, the last digits are written directly after the "/" sign for inner diameters greater than 5X99= 495mm. Example: 618/750  Single row ball bearing with an inside diameter of 750 mm. These rules apply to all bearing types.
  
  
  
  BEARING TYPE DESCRIPTION

• The starting characters in the display determine the bearing type. Accordingly, if the first characters

• 6  or  16  if it starts with , the bearing is a single row ball bearing
  4  If it starts with , the bearing is a double row ball bearing. 
  one  or  2nd  If it starts with , the bearing is a self-aligning ball bearing.
  7  If it starts with , the bearing is an angular contact ball bearing.
  3  If it starts with , the bearing is a double row angular contact ball bearing.
  Q  If it starts with , the bearing is a four-point contact ball bearing.
  N  or  319  If it starts with , the bearing is a cylindrical roller bearing.
  HK  or  N  or  RNA  If it starts with , the bearing is a needle roller bearing.
  K  or  T  or  3  If it starts with , the bearing is a tapered roller bearing.
  2nd  If it starts with , the bearing is a spherical roller bearing.
  5  If it starts with , the bearing is an thrust ball bearing.
  8  If it starts with , the bearing is an thrust roller bearing.
  29  If it starts with , the bearing is an axial spherical roller bearing.
  
  DISPLAY OF SPECIAL SHAPES OF BEARINGS

• The alphabetic letters at the end of the bearing designation mean:

• K   : inner diameter tapered bearing

• Z   : One side closed bearing

• 2Z : Two-sided closed bearing

• N   : One side of the bearing has a ring slot

• NR  : Bearing has circlip with circlip seat on one side

• M   : Balls or rollers in bronze cage

• L     : Ball or rollers in alloy cage

• T     : Balls or rollers in Synthetic resin cage