You can learn a lot about a bearing just from its part number. A typical bearing is the 6203ZZ bearing. This part number can be divided into it's components: 6203ZZ which means: Type Code Series Bore Suffix The type code indicates the type of bearing. While each manufacturer uses their own numbers, there are a few numbers that could be considered standard in the industry.
Self-Aligning Ball Bearing This kind of ball bearing has a spherical outer race, allowing the axis of the bearing to "wander around". This is important because misalignment is one of the big causes of bearing failure.
Spherical Roller Bearing
Double-Row Angular Contact Ball Bearing 3 Designed to take axial as well as radial loads.
Double-Row Ball Bearing 4 Designed for heavy radial loads.
Thrust Ball Bearing 5 Intended for exclusively axial loads.
Single-Row Deep Groove Ball Bearing 6 Typical ball bearing. Handles light axial loads as well as radial loads.
Single-Row Angular Contact Bearing 7 For axial (one direction only!) as well as radial loads.
Felt Seal To assure that the entire inside edge of the seal touches the inner ring, the inner ring is enlarged. If a bearing of more normal proportions is required, the outer ring is also enlarged, and the bearing is referred to as a "wide cup" bearing. Tapered Roller Bearing 32 This is the kind of wheel bearings used in cars. The rollers are not cylindrical, but conical. They handle large raidal and axial loads. Inch (Non-Metric) Bearing Cylindrical Roller Bearing Instead of balls, cylindrical rollers are used. These bearings can handle much more radial load, but can handle much less axial load, than ball bearings. Varies
Double-Row Roller Bearing NN Handles greater radial loads than standard cylindrical roller bearings.
Needle Roller Bearing NA Needle bearings are basically roller bearings, but the rollers are much smaller, making the bearing more compact. Varies
Type 6, "single-row deep groove", is perhaps the most common type of bearing. If the bearing is an inch bearing (the first digit in the number is an R), then the size is the digit or digits immediately following the R, in 16ths of an inch. An R8-2RS bearing, for example, has an 8/16th or 1/2 inch bore. If the first digit is a number, however, it is a metric bearing, and the second digit is the series, which reflects the robustness of the bearing. The series are, from lightest to heaviest: 8 Extra thin section 9 Very thin section 0 Extra light 1 Extra light thrust 2 Light 3 Medium 4 Heavy Yes, they go in that order. Gotta keep things simple, you know. Each of these series also establishes a relationship between the bore size, outer diameter, and thickness of the bearing, in accordance with ISO standards. I have no idea what they are. The third and fourth digits indicate the bore size in millimeters. Except for 0 through 3, the bore size is simply five times the third and fourth digits together. 0 through 3, however, are different: 00 10mm 01 12mm 02 15mm 03 17mm If there is no fourth digit - for example, a 608 bearing, a common roller skate bearing then the size is the last digit in millimeters.
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 And then there are the completely off-the-wall bearing numbers, like 499502H. I have no idea what that number is supposed to mean, but it applies to what is basically an R102RS bearing, only a bit thicker and with a groove and snap ring.
Common Skate Bearings
Number 608 627 688 698 Bore O.D. Width (mm) (mm) (mm) 8 22 7 7 22 7 8 16 4 8 19 6
All these bearing numbers start with 6, which tells us they're Single-row deep groove ball bearings. The second digits tell us the...