Many people are often confused by numbers written to describe bearings. For some, they believe it is insignificant while for some others, they know it is important but they just do not know what it represents. That is simply what we will be addressing in this article. To start with, these numbers are used to categorize and describe bearings so that it becomes easier to know what a bearing is used for by just reading its code.
Also, these codes let you know if the bearing is suitable for what you intend to use it for. Perhaps, the most significant importance of such codes is that they are used as a standard for describing bearings regardless of who the manufacturer or maker is.
For instance, let us analyse a bearing with a code of 6902.
S 6902 2RS
In the above, S represents the prefix. 6902 is the code and 2RS is the suffix.
The prefix usually convey certain information. There are different types of prefixes.
K – Used for cage with roller elements
L – Used to convey a removable bearing ring
R – Denotes a ring with roller set
S – Roll body of stainless steel
W – Stainless steel deep groove ball bearing
The first number, i.e. ‘6’ represents the type of bearing. Often times, a bicycle bearing is denoted with a ‘6’ and can be interpreted as a “Deep Groove”. Conversely, a ‘7’ can be interpreted as a “Single Row Angular Contact”.
The second number, i.e. ‘9’ tells us about the series of the bearing. It is also an indication of how robust the bearing is.
9 – Very thin section
0 – Extra light
1 – Extra light thrust
2 – Light
3 – Medium
4 – Heavy
The third digit and fourth digit, i.e. ‘02’ defines the size of the bore of the bearing. It usually ranges from 00 to 03.
00 – 10mm
01 – 12mm
02 – 15mm
03 – 17mm
It is important to state that numbers above 03 exist. However, their value is usually about 5 times that of the last two digits in the bearing code.
Like prefix, there are different suffixes.
K – Means that a bearing has taper bore
P2 – Impressive precision
E – Indicates that the design is reinforced
Z – One side is open, the other side has a metal seal
2 Z/ZZ – There is a metal seal on both sides
RS – Rubber seal on a side, the other side is open
2RS – Rubber seal on both sides