6308 bearing dimensions
A 6308 bearing is 40 mm bore × 90 mm outside diameter × 23 mm wide (1.575 × 3.543 × 0.906 in). The sealed version is 6308-2RS; the shielded version is 6308-ZZ.
6308 at a glance
Boundary dimensions in millimetres and inches, and the common closure designations.
- Bore, d
- 40 mm 1.5748"
- Outside diameter, D
- 90 mm 3.5433"
- Width, B
- 23 mm 0.9055"
- Section height, (D − d)/2
- 25 mm 0.9843"
- Series
- 63 series medium
- Bore code
- 08 08 × 5 = 40 mm
- Sealed, both sides
- 6308-2RS
- Shielded, both sides
- 6308-ZZ
- Open
- 6308 no closures; any version may add C3 for extra internal clearance
Reading the number 6308
Every deep groove ball bearing number follows the same pattern: type, dimension series and bore code, then suffixes.
Seals, shields and suffixes
Suffixes add closures and internal clearance. They do not change the boundary dimensions: a sealed and an open bearing of the same number are interchangeable in size.
| Suffix | Meaning | 6308 example |
|---|---|---|
| Open (no suffix) | No seals or shields. Can be relubricated, or run in an oil bath; the housing needs its own seal against dirt. | 6308 |
| Z | One metal shield, on one side only. | 6308-Z |
| ZZ, 2Z | Metal shields on both sides. Non-contact, so low friction; keeps out larger dirt. Usually greased for life. | 6308-ZZ |
| RS | One rubber contact seal, on one side only. | 6308-RS |
| 2RS, 2RS1, 2RSH, 2RSR, DDU, LLU | Rubber contact seals on both sides. Better than shields against fine dirt and splashing water, with a little more friction. Usually greased for life. | 6308-2RS |
| C3 | Radial internal clearance greater than normal (CN). Used with tight shaft or housing fits, or where the inner ring runs hotter than the outer ring. | 6308-2RS C3 |
6308 in other brands
The sealed and shielded versions as each maker writes them. All share the same boundary dimensions.
| Maker | Sealed both sides | Shielded both sides |
|---|---|---|
| SKF | 6308-2RSH | 6308-2Z |
| FAG (Schaeffler) | 6308-2RSR | 6308-2ZR |
| NSK | 6308DDU | 6308ZZ |
| NTN | 6308LLU | 6308ZZ |
| Koyo (JTEKT) | 6308-2RS | 6308ZZ |
| Timken | 6308-2RS | see catalogue |
Seal designs and suffixes vary by maker, size range and product generation, for example contact versus low-friction seals. Confirm the exact designation in the maker's catalogue before ordering.
Same 40 mm bore, other series
Bearings that fit the same shaft. A heavier series carries more load in a bigger housing bore; a thin-section series saves space and weight.
63 series
Common questions
What size is a 6308 bearing?
40 mm bore, 90 mm outside diameter and 23 mm wide, which is 1.575 × 3.543 × 0.906 in.
What does 2RS mean on a 6308 bearing?
6308-2RS has rubber contact seals on both sides. 6308-ZZ (also written 6308-2Z) has metal shields on both sides. Both have the same 40 × 90 × 23 mm dimensions.
Is 6308-2RS the same as 6308-ZZ?
They are the same size and interchangeable in a housing. The sealed 6308-2RS keeps out fine dirt and water better; the shielded 6308-ZZ runs with less friction.
What is the SKF equivalent of 6308-2RS?
SKF writes it 6308-2RSH; FAG 6308-2RSR, NSK 6308DDU, NTN 6308LLU and Koyo 6308-2RS. Check the maker's catalogue for the exact seal type.
What does the number 6308 mean?
6 is the deep groove ball bearing type, 3 is the medium dimension series, and 08 × 5 = 40 mm (from 04 up, multiply by 5).
Which bearings have the same bore as 6308?
6808, 6908, 6008, 6208 also have a 40 mm bore, with different outside diameters and widths.