How A Bearing is Named ?

How a bearing is named?

Though it is very simple device supporting a rotating or sliding shaft, but its nomenclature is very intriguing. A bearing name usually contains initial 4 numbers. So what does each number convey? Each has its own value and they tell a lot about a particular bearing. (we are talking about the metric bearings here, so the dimensions are in mm). The first number tells us about the type of bearing. The second number denotes the cross-section/series. The third and fourth number taken together tells about the bore or inner diameter. Let’s take an example:

I have a bearing with number on this bearing is 6001; we go through each number one step at a time.

First number tells about the type of bearing, here is a list of different type of bearings;

1 = Double Row self-aligning
2 = Double Row self-aligning (wide)
3 = Double Row
4 = Angular Contact
6 = Single Row Deep Groove
7 = Angular Contact

So, from the list we come to know that our sample is a “Single Row Deep Groove” bearing.


Now coming on to the second number, which signifies the cross-section / series:

18 = Thin Section, Light
19 = Thin Section, Medium
0 = Very Light
2 = Light
3 = Medium
4 = Heavy

From the above list we know that we have a “very light” bearing (0).


The third and fourth number together signifies the bore of the bearing:
00 = 10 mm
01 = 12 mm
02 = 15mm
03 = 17 mm
For 20-480 mm bore bearings: Last 2 digits x 5 = Bore (mm) i.e. – if the bearing number was 04 (04 x 5 = 20 mm), 05 (05 x 5 = 25 mm), and so on...

Our bearing has last two digits as 01, which tells that it has a bore of 12 mm.

What if the bearing has only three numbers instead of four numbers? Like 607. The answer is simple; we can know what first two numbers tell. Since the fourth number is not there, the third numbers itself is the bore of the bearing. So a 607 bearing is a “Single row deep groove, and is very light and is having bore of 7 mm”.

But that is not the end; we may have these numbers followed by few letters (alphabets). The last letters indicate something special about the bearing.

For example:
Z Single shielded
ZZ Double shielded
RS Single sealed
2RS Double sealed
V Single non-contact seal
VV Double non-contact seal
DDU Double contact seals
NR Snap ring and groove
M Brass cage

So, now what does the bearing suggests – 6310-2RS …………… ?