21308 Bearing Dimensions
21308 spherical roller bearing: bore 40 mm, dimensions 40x90x23 mm (FULI catalog). Designation breakdown, bore options and size-equivalent codes.
21308 specifications
| Bore d | 40 mm |
|---|---|
| Outside diameter D | 90 mm |
| Width B | 23 mm |
| Seal / shield options | Open |
| Material | GCr15 chrome bearing steel (rings and rolling elements) |
| Precision | P0 (standard); P6 on request |
| Radial clearance | C0 (standard); C3 on request |
Load ratings & speed
| Dynamic load rating Cr | 104 kN |
|---|---|
| Static load rating C0r | 108 kN |
| Speed ratings | 7,000 / 9,500 rpm — two catalogue speed columns; lubrication basis not stated |
| Weight | 0.75 kg — approx. |
Values from FULI's catalog; confirm for your application.
Nearby 21300 series sizes: 21311 bearing · 21312 bearing
Grease quantity for 21308: bearing grease fill calculator.
Buying 21308 in quantity? See bearing wholesale supplier for pricing by quantity and shipping, and bearing manufacturer in China for how to check the factory.
How to read the 21308 designation
| Segment | Meaning |
|---|---|
| 2 | Spherical roller bearing (double row, self-aligning) |
| 13 | Dimension series 13 |
| 08 | Bore code 08 → 40 mm bore. ISO bore code (00–03 = 10/12/15/17 mm; 04 and above = code × 5 mm). |
21308 interchange
21308 is an ISO designation: bore d, outside diameter D and width B are the same at each maker. The letters each maker adds are design and cage codes, not seal codes; K marks a tapered bore, and each maker marks the oil groove and holes in its own way. Send us the full number on your old bearing and we confirm the match.
Brand names are trademarks of their respective owners. FULI is not affiliated with, authorized by or endorsed by these companies. Part numbers are shown for interchange reference only. FULI dimensions, load ratings and speeds come from the FULI catalog.
Tolerances and fits for 21308
FULI makes 21308 to P0 as standard, with P6 on request. P0 is the Normal tolerance class of ISO 492; P6 limits are tighter. These are the P0 limits for the 40 × 90 × 23 mm size.
| Dimension | Nominal, mm | Deviation, µm | Limits, mm |
|---|---|---|---|
| Bore d (Δdmp) | 40 | 0 / −12 | 40.000 / 39.988 |
| Outside diameter D (ΔDmp) | 90 | 0 / −15 | 90.000 / 89.985 |
| Width B (ΔBs) | 23 | 0 / −120 | 23.000 / 22.880 |
Δdmp and ΔDmp: deviation of the mean bore and mean outside diameter in one radial plane. ΔBs: inner ring width; the outer ring width has the same limits.
Shaft and housing fits (general guidance)
For an inner ring that turns with a solid steel shaft under normal load, bearing makers’ fit tables give 40 k5 for the shaft of 21308. The housing bore is usually H7, or J7 where the outer ring must not creep.
| Seat | Deviation, µm | Limits, mm | Fit with 21308 |
|---|---|---|---|
| Shaft 40 k5 | +13 / +2 | 40.013 / 40.002 | 2 to 25 µm interference |
| Housing 90 H7 | +35 / 0 | 90.035 / 90.000 | 0 to 50 µm clearance |
| Housing 90 J7 | +22 / −13 | 90.022 / 89.987 | 13 µm interference to 37 µm clearance |
Taking the loosest and the tightest combination of limits, a P0 21308 on a 40 mm k5 shaft has 2 to 25 µm interference. Its outer ring has 0 to 50 µm clearance in an H7 bore and 13 µm interference to 37 µm clearance in a J7 bore.
This is general guidance, not a FULI specification. Heavy or shock loads, a hollow shaft, a thin-walled, split or light-alloy housing, or a large temperature difference between shaft and housing call for other classes, and the drawing of your machine takes priority. A tight shaft fit or a hot housing uses up internal clearance, and that is when C3 is chosen instead of C0.
If the outer ring turns and the shaft stands still, as in an idler pulley or a wheel hub, the fits are reversed: the housing gets the interference fit (for example N7 or P7) and the shaft a sliding one (g6 or h6).
Sources: ISO 492 tables as printed in the NTN catalogue CAT. No. 2203/E (Tables 6.4 and 6.5) and the RKB tolerance catalogue; ISO 286-2 for the seats; SKF and NTN fit tables for the shaft and housing classes.
21308 compared with nearby sizes
21308 measures 40 × 90 × 23 mm: bore d, outside diameter D and width B. Other spherical roller bearings on this site for the same 40 mm shaft are 22208 (40 × 80 × 23 mm) and 22308 (40 × 90 × 33 mm).
22308 is the next heavier choice for a 40 mm shaft, with the same 90 mm outside diameter and 10 mm more width (33 mm). In FULI's catalog 22308 has a dynamic load rating of 150 kN against 104 kN and a weight of about 1.05 kg against 0.75 kg for 21308.
22208 is the lighter option on the same shaft, with an outside diameter 10 mm smaller (80 mm) and the same width, for housings with less room. In FULI's catalog 22208 has a dynamic load rating of 96 kN against 104 kN and a weight of about 0.53 kg against 0.75 kg for 21308.
22210 has the same 90 mm outside diameter with a 50 mm bore, so it fits the same housing bore on a larger shaft.
In the 213 series the sizes either side of 21308 are 21311 for a 55 mm shaft.
| Model | Compared with this page | d × D × B (mm) | Cr (kN) | Weight (kg) |
|---|---|---|---|---|
| 21308 | This page | 40 × 90 × 23 | 104 | 0.75 |
| 21311 | Next size up | 55 × 120 × 29 | 158 | 1.70 |
| 22208 | Same bore | 40 × 80 × 23 | 96 | 0.53 |
| 22308 | Same bore | 40 × 90 × 33 | 150 | 1.05 |
| 22210 | Same outside diameter | 50 × 90 × 23 | 104 | 0.63 |
Cr and weight from FULI's catalog; — = not listed on this site.
21308 weight, load ratings and speed
FULI's catalog gives the weight of 21308 as about 0.75 kg, so 100 bearings weigh about 75 kg and 1,000 about 750 kg before packing. The cylindrical bore (W33) and tapered bore (K/W33) versions share this catalog line.
21308 has a dynamic load rating Cr of 104 kN and a static load rating C0r of 108 kN. Cr is the load used to work out rating life; C0r is the reference for loads carried while the bearing is stationary or turning slowly. The catalog lists two speed values, 7,000 and 9,500 rpm, without stating the lubrication for each column.
Values from FULI's catalog; confirm for your application.
21308 bore and clearance versions
FULI's catalog lists 21308 in two bore versions on one line, both 40 × 90 × 23 mm: 21308W33 with a cylindrical bore and 21308K/W33 with a 1:12 tapered bore. W33 marks the lubrication groove and holes in the outer ring. The K version is mounted on an adapter sleeve, a withdrawal sleeve or a tapered shaft seat. Radial clearance is C0 as standard and C3 on request.
| Designation | What it is |
|---|---|
| 21308W33 | Cylindrical 40 mm bore, lubrication groove and holes, C0 clearance |
| 21308K/W33 | Tapered bore 1:12 for sleeve mounting, lubrication groove and holes |
| 21308W33 C3 | Cylindrical bore with C3 radial clearance |
| 21308K/W33 C3 | Tapered bore with C3 radial clearance |
21308 dimensions in inches
The nearest common inch shaft size to the 40 mm bore of 21308 is 1-9/16 in (39.69 mm), 0.31 mm smaller than the bore, so 21308 would be loose on it. Inch shafts need an inch bearing, not a metric one with a sleeve or shim.
| Dimension | Millimetres | Inches |
|---|---|---|
| Bore d | 40 mm | 1.5748 in |
| Outside diameter D | 90 mm | 3.5433 in |
| Width B | 23 mm | 0.9055 in |
Converted at 1 in = 25.4 mm and rounded to four decimals. The bearing itself is made to the millimetre sizes.
Grease for 21308
Relubricating 21308 from the side takes about 10.3 g each time by the formula in our grease calculator: 0.005 × D × B = 0.005 × 90 × 23. 21308W33 has a lubrication groove and holes in the outer ring; when grease goes in through them the formula is 0.002 × D × B, about 4.14 g for 21308.
How FULI supplies 21308
The standard 21308 from FULI has GCr15 chrome steel rings and rollers, P0 precision and C0 radial clearance, with P6 and C3 on request.
Rings are marked with a brand you are authorised to use, with the FULI brand, or left neutral, as your order states. The box is printed with the model, precision class and brand.
Inquiries that leave out the prefix or suffix letters are the usual cause of a wrong quote, so write the full designation, for example 21308K/W33 C3.
Tools and guides for 21308
Typical applications
- Crushers and vibrating screens
- Conveyor drums
- Fans and blowers
- Gearboxes
- Paper and textile machinery
FAQ
What is the difference between 21308 and 22308?
Both fit a 40 mm shaft. 21308 is 40 × 90 × 23 mm and 22308 is 40 × 90 × 33 mm, so 22308 has the same 90 mm outside diameter and 10 mm more width (33 mm). In FULI's catalog 22308 has a dynamic load rating of 150 kN against 104 kN and a weight of about 1.05 kg against 0.75 kg for 21308. Choose 22308 for a higher load where the housing has room for it; 21308 keeps the housing smaller.
What is the difference between 21308 and 22208?
Both fit a 40 mm shaft. 21308 is 40 × 90 × 23 mm and 22208 is 40 × 80 × 23 mm, so 22208 has an outside diameter 10 mm smaller (80 mm) and the same width. In FULI's catalog 22208 has a dynamic load rating of 96 kN against 104 kN and a weight of about 0.53 kg against 0.75 kg for 21308. 22208 suits a housing with less room; 21308 carries more load.
What size is 21308 in inches?
21308 is 1.5748 × 3.5433 × 0.9055 in (40 × 90 × 23 mm, d × D × B). The nearest common inch shaft size to the 40 mm bore of 21308 is 1-9/16 in (39.69 mm), 0.31 mm smaller than the bore, so 21308 would be loose on it. Use an inch bearing on an inch shaft.
How much does 21308 weigh?
About 0.75 kg in FULI's catalog, so 100 pieces weigh about 75 kg before packing. The cylindrical bore (W33) and tapered bore (K/W33) versions share this catalog line.
How much grease does 21308 need?
About 10.3 g each time it is relubricated from the side (0.005 × 90 × 23).
Is 21308 the same size across brands?
Bore d, outside diameter D and width B are the same: 21308 is an ISO designation. The letters each maker adds (SKF E or CC, NSK CE4, EAE4 or CDE4, NTN EAD1, Koyo RZ, NACHI EX or E, FAG E1-XL) are design and cage codes, not seal codes. K marks a tapered bore, and the oil groove and holes are marked differently by each maker (SKF W33, NSK E4, NTN D1).