Designation of Bearings

DESIGNATION OF BEARINGS

A bearing number has four parts to it which includes four numbers and a set of letters. Each of the first two numbers stand for something, the last two designate size. The letters dictate the variation of the bearing. These letters can also be followed by more letters designating internal clearance.

In detail:

First number (will be a 1-7) designates the bearing type:
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

The second number designates the series, or cross section. This is basically equivalent to the second number of a tire rating; it's a ratio of the bore to the width of the bearing, which also controls the O.D. of the bearing. The larger the cross section, the larger the O.D. of the bearing.

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

The third number (which is a set of two numbers) indicates the bore (in mm) of
the bearings. All bearings are designated with metric standards, not inches.
Numbers are as follows:
00 = 10 mm
01 = 12 mm
02 = 15mm
03 = 17 mm
For 20-480mm 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)

The letters after the number indicate the variation. These change from manufacturer to manufacturer, but here are some of the common ones:

Plain -- No Shield
Type Z -- One Shield (normally will have metal shields)
Type 2Z -- Two Shields (one on each side)
Type RS1 -- One Seal (normally the R indicates rubber)
Type 2RS1 --Two Seals (one on each side)
Type LL -- Two Seals (just another manufacturer's designation)
CD -- 15 degree contact angle (for angular contact)
ACD = 25 degree contact angle (for angular contact)

The bearings can also have a C2, C3, C4 or C5 designation after the bearing number. This indicates that the internal fit (the inner race to ball to outer race) is not standard. If your bearing has one of these designators, make sure you get a bearing with the same designator. A C2 is less than standard clearance, while a C3, 4, and 5 are larger than standard.