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Bearing Nomenclature

Here is some information on bearing types and nomenclature that I thought
everyone might enjoy. If you know the bearing number, you don't need to go to
the dealer, just go to a local bearing distributor or a place that sells gear
boxes. They should have them or be able to get them in a day.

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.

If anybody has a set of old bearings and can mic them up (ID, OD and width) I
can cross reference them to a standard bearing number.

Boys and girls, our next lesson will be on proper interference and clearance

Paul Waterloo                    TEL: (860) 267-7714
HydroAire Incorporated           FAX: (860) 267-7387
875 Old Hartford Rd
Colchester, CT  06415          EMAIL: 74543.407@compuserve.com