Bearing Bore Code Chart

What it is

Most metric rolling bearings follow a numbering system based on ISO 15 boundary dimensions. In a basic number such as 6205, the first digits give the bearing type and series (62 = deep groove ball, 02 series). The last two digits are the bore code. For codes 04 and up, the bore in millimeters is the code times 5. Codes 00 to 03 are fixed values. Prefixes and suffixes (shields, seals, clearance) are added around the basic number.

How to read it

1. Find the basic number on the bearing ring or box, ignoring suffixes such as 2RS or C3.
2. Take the last two digits.
3. If they are 00, 01, 02 or 03, read the bore from the chart.
4. If they are 04 or higher, multiply by 5. Example: 6210 has a bore of 10 x 5 = 50 mm.
5. Confirm by measuring the bore with calipers or a bore gauge.

Bore code chart

Exceptions

• Small bores: for bores under 10 mm, a single last digit is the bore in mm. A 608 has an 8 mm bore.
• Slash sizes: a slash shows the bore directly in mm, such as 62/22 (22 mm) or 62/28 (28 mm). These are the in-between sizes that the x5 rule cannot express.
• Large bores: at 500 mm and above the bore is written after a slash, such as /500.
• Inch bearings (for example R-series ball bearings and tapered roller cup and cone numbers) do not follow this rule. Look them up by part number.

Key points

• The bore code tells you the bore only. The outside diameter and width depend on the series digits.
• Brand prefixes and suffixes vary. The basic number is usually common across brands.
• Measure the shaft as well as the old bearing. A worn shaft changes the fit.

Common mistakes

• Multiplying 00 to 03 by 5.
• Reading a 62/22 as a 6222.
• Applying the metric rule to an inch bearing.

Governing standards: ISO 15 (radial bearing boundary dimensions); ISO 355 (tapered roller bearings, metric); bearing maker catalogs for designations.

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.