A metric bearing basic designation can identify a bearing type, dimension series, and bore code. The bore code is the first filter when you know the shaft size. It does not settle the housing envelope, load direction, internal clearance, closure, cage, precision, or maker-specific ordering suffixes.
The Bearing Finder by Bore Size searches only audited table rows. It matches an exact shaft bore, applies optional outside-diameter and width limits, and decodes every surviving designation back to the requested bore. If the table does not contain the bore, it gives a needs-source result instead of building a plausible number.
1. How bearing numbering encodes size
Standard four-digit and five-digit metric designations use the last two digits as the bore code. Four values are exceptions: 00 is 10 mm, 01 is 12 mm, 02 is 15 mm, and 03 is 17 mm. From code 04 through code 96, multiply the code by 5 to get the bore in millimetres. Code 04 is 20 mm, code 05 is 25 mm, and code 10 is 50 mm.
The three-digit miniature deep groove ball line uses the last digit as the bore directly. 608 has an 8 mm bore. 638 also has an 8 mm bore, not 38 mm. Slash notation carries a literal bore when the normal code rule does not apply. The tabulated 619/500 designation has a 500 mm bore.
2. The dimension series ladder
The audited deep groove ball data describes the 6000 line as extra-light, 6200 as light, 6300 as medium, and 6400 as heavy. At a shared bore, moving along that ladder increases outside diameter and usually width and load capacity. The series is an envelope choice, not a ranking of overall suitability.
For a 25 mm bore, the table progresses from 6005 at 47 x 12 mm to 6405 at 80 x 21 mm. The dynamic load rating in the source rows increases from 11.9 kN to 35.8 kN. The larger row needs more housing space, so the smallest or highest-capacity row is not automatically the correct one.
3. The full 25 mm table
Twenty rows in the audited table have a 25 mm bore. Width means bearing height H on the thrust rows and T dimension on the tapered rows. The tapered roller source uses a different rating-life convention, so its load cells remain not tabulated rather than being mapped into ISO 281 C.
| Designation | Type | OD mm | Width mm | Dynamic C kN | Static C0 kN |
|---|---|---|---|---|---|
| 51105 | Thrust ball | 42 | 11 H | 18.2 | 39 |
| 6005 | Deep groove ball | 47 | 12 | 11.9 | 6.55 |
| 51205 | Thrust ball | 47 | 15 H | 26.5 | 50 |
| 1205 | Self-aligning ball | 52 | 15 | 14.3 | 4 |
| 6205 | Deep groove ball | 52 | 15 | 14.8 | 7.8 |
| 7205 | Angular contact ball | 52 | 15 | 15.6 | 10 |
| NU205 | Cylindrical roller | 52 | 15 | 32.5 | 27 |
| QJ205 | Four-point contact ball | 52 | 15 | 27 | 21.2 |
| 30205 | Tapered roller | 52 | 16.25 T | Not tabulated | Not tabulated |
| 22205 | Spherical roller | 52 | 18 | 49.9 | 44 |
| 32205 | Tapered roller | 52 | 19.25 T | Not tabulated | Not tabulated |
| 33205 | Tapered roller | 52 | 22 T | Not tabulated | Not tabulated |
| 1305 | Self-aligning ball | 62 | 17 | 19 | 5.4 |
| 6305 | Deep groove ball | 62 | 17 | 23.4 | 11.6 |
| 7305 | Angular contact ball | 62 | 17 | 26.5 | 15.3 |
| NU305 | Cylindrical roller | 62 | 17 | 46.5 | 36.5 |
| QJ305 | Four-point contact ball | 62 | 17 | 42.5 | 30 |
| 30305 | Tapered roller | 62 | 18.25 T | Not tabulated | Not tabulated |
| 32305 | Tapered roller | 62 | 25.25 T | Not tabulated | Not tabulated |
| 6405 | Deep groove ball | 80 | 21 | 35.8 | 19.3 |
The order above follows outside diameter, then width, then designation. All twenty fit a 25 mm shaft. They do not serve the same load direction, misalignment, speed, or mounting duty.
4. Choosing the type once the size is settled
The audited bearing-type profiles describe duty with radial load, axial load, and misalignment tolerance. Deep groove ball is medium radial, low-medium axial, and low misalignment. Angular contact ball is medium radial, high axial, and low misalignment. Cylindrical roller is high radial, no axial, and low misalignment. Spherical roller is very-high radial, medium axial, and high misalignment.
Self-aligning ball is low-medium radial, low axial, and high misalignment. Tapered roller is high radial, high axial, and low misalignment. Thrust ball is no radial, high axial, and no misalignment. Four-point contact ball is medium radial, high axial, and low misalignment. These profile fields help narrow the type. They do not replace application load, life, fit, lubrication, and mounting calculations.
5. What the basic number leaves open
The basic designation does not select seals, shields, radial internal clearance, cage, precision, lubricant, or internal design. At a 25 mm bore, the copied ISO 5753-1 deep groove ball table gives CN clearance as 5 to 20 microns and C3 as 13 to 28 microns for the range above 24 mm through 30 mm. Those bands apply to deep groove ball bearings in this data. Roller bearing clearance tables are different.
CN is the normal class when no suffix is shown. C3 is greater than normal and is common where a hot shaft or interference fit reduces operating clearance. The right class depends on fits and running temperature. Use the Bearing Decoder to read the maker-specific closure, clearance, cage, and precision suffixes on an existing number.
6. Brand namespaces
The ISO basic number is shared across makers, but the full ordering number is not. Each maker uses its own prefixes and suffixes for closure, clearance, cage, lubricant, precision, internal design, and other details. A shared basic number proves a common standard size. It does not prove that two complete ordering numbers are interchangeable.
Load and speed values in this finder are source-catalog baselines for an open variant where tabulated. Enhanced E and EC designs typically carry 10 to 30 percent higher dynamic capacity and are different parts. Cross-brand matching requires a separate comparison of the complete ordering numbers, application duty, and current maker documentation.
7. Before you order
Confirm the shaft diameter at the bearing seat and the housing bore. Check shaft and housing tolerance, fits, internal clearance after mounting, seal or shield, cage, lubricant, alignment, speed, load direction, and expected bearing life. On a thrust row, read the listed width as height H. On a tapered row, read it as T.
Then compare the complete ordering number with the maker's current catalog row and the physical part label. A basic designation is not enough to order a fully specified bearing. A needs-source result means this curated table does not contain the requested bore or envelope. It does not mean the bearing does not exist.
8. Sources
- SKF Rolling Bearings product tables, Publication 17000 EN, 2021 edition.
- SKF Bearings and Mounted Products, deep-groove radial internal-clearance table. The 24 through 30 mm bore row gives CN 5 to 20 microns and C3 13 to 28 microns, matching the 25 mm guide example.
- Timken Tapered Roller Bearing Catalog 10481, 2021, single-row metric tables, printed pp. 394-396.
- Timken Metric Tapered Roller Bearings, official metric dimensions table. The 25 mm rows independently corroborate 30205, 32205, 33205, 30305, and 32305.
- ISO 15, boundary dimensions for radial bearings.
- ISO 5753-1:2009, radial internal clearance, limited here to deep groove ball bearings.
- ISO 5593, bearing vocabulary, and ISO 281:2007, rating life, as cited in the audited bearing-type data.
The maker's current catalog row and the physical part label control the final order.