Bearing Number Designations by Dennis Turk (with permission)

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Bearing numbers have been universal for a very long time.

Example: 88504

The 5 in the number indicates the OD and the 04 indicates the ID and these are metric dimension bearings.


The 88 before the 504 may indicate a special seal or an offset inner ring as in agriculture bearings.

They can also mean the basic bearing dimensions have something different about them, as in a special inner diameter or outer diameter. There are bearings that havea metric OD and an inch ID and also the reverse of this.

Craftsman drill press I had used a bearing that was metric on the outside and inch on the inside.

If the bearing number has a suffix then these indicate seal or shield configurations. A 6203 2RS is a bearing with two rubber seals and etc. Different manufactures use different codes for seals and shields but the basic bearing number will always be the same as long as there is no alteration of the basic bearing size in ID OD and width. Same goes for prefixes it’s an mfg'scall what they call the item.

There are as many variations in bearings as there are stars in the sky. I have been through one of these under drives and replaced the bearings but it was someyears ago and I don’t remember the particulars details. If you find are placement bearing with the same numbers it’s a good chance it’s the same bearing.

Turk
 
That is not entirely correct. The last three digits of the bearing number indicate the bore, od, and width of the bearing, excluding any extended inner races. The 88 prefix describes a bearing with extended inner races on both sides of the bearing, while the 87 prefix describes a bearing with only one extended inner race.

6200 series bearings are bearings that can sometimes have special bores (usually in fractional measurements. For example, a 6202-1/2 bearing would be a standard 6202 but with a 1/2" bore. When purchasing 6200 series bearings, the bore needs to be measured to insure the correct size, as the bearing will not be stamped with the special bore information.

Greg
 
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