Bearing Numbers Decoded

What it is

Most metric ball and roller bearings carry a basic number that encodes the bearing type, its dimension series (how wide and how large the outside diameter is for a given bore) and its bore. Prefixes and suffixes added by the manufacturer describe seals, shields, internal clearance, cage material, snap rings and precision. The boundary dimensions behind the basic number come from ISO 15 (radial bearings) and ISO 355 (metric tapered roller bearings), so a 6205 from one maker has the same bore, OD and width as a 6205 from another. Suffixes are not fully standardized — each brand uses its own codes for the same feature.

How to identify

Read the number on the outer ring face or the seal. Example: 6205-2RS C3.

1. First digit(s) — type. 6 = single-row deep groove ball. 7 = angular contact ball, 2 = spherical roller (22xxx, 23xxx), 3 = metric tapered roller (30xxx, 32xxx), 1 = self-aligning ball, 5 = thrust ball. Letters NU, NJ, N and NUP indicate cylindrical roller bearings.
2. Next digit — dimension series. In the 6xxx family: 60xx = extra-light, 62xx = light, 63xx = medium, 64xx = heavy. Higher numbers mean a larger OD and width for the same bore. 618xx, 619xx and 160xx are thin-section series.
3. Last two digits — bore code. See the table.
4. Suffixes. Closures, clearance and other features (table).

Bore codes and common suffixes

Key points

• Basic number = interchangeable dimensions. Suffixes = features that may or may not matter to the application. Always ask what the old bearing's suffixes were.
• C3 clearance is common in electric motors and where the inner ring runs hotter than the outer ring or has a tight fit. Do not substitute normal clearance for C3 without checking.
• Shields (ZZ) allow higher speeds with less drag; contact seals (2RS) keep out contamination better but run warmer and slower. Check the speed rating before switching.
• Inch bearings (R-series, 1600 series, inch tapered cone and cup sets) use different numbering — see the inch bearing sheets.
• If the number is worn off, measure bore, OD and width and look them up by dimension, then confirm the type.

Common mistakes

• Treating 6205-2RS and 6205-ZZ as identical in a washdown or dusty application.
• Dropping the C3 suffix when quoting a motor bearing.
• Misreading the bore code as millimeters (6205 has a 25 mm bore, not 5 mm).
• Assuming one brand's seal suffix means the same thing in another brand's catalog.

Governing standards: ISO 15 (radial bearing boundary dimensions); ISO 355 (metric tapered roller bearings); ISO 5753-1 (radial internal clearance); ABMA 20 (radial ball and roller bearings, metric). Manufacturer designation guides for suffixes.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.