6306 Bearing Dimensions
6306 is a deep groove ball bearing with a 30 mm bore, 72 mm outer diameter and 19 mm width (30×72×19 mm, ISO 15). Open, ZZ, 2RS variants, designation breakdown, size-equivalent codes. Quote.
6306 specifications
| Bore d | 30 mm |
|---|---|
| Outside diameter D | 72 mm |
| Width B | 19 mm |
| Seal / shield options | Open; ZZ (two metal shields); 2RS (two rubber seals) |
| Material | GCr15 chrome bearing steel (rings and rolling elements) |
| Precision | P0 (standard); P6 on request |
| Vibration grade | Z3V3 (standard); other grades on request |
| Radial clearance | C0 (standard); C3 on request |
Load ratings & speed
| Dynamic load rating Cr | 24.03 kN |
|---|---|
| Static load rating C0r | 14.40 kN |
| Limiting speed, grease | 9,500 rpm |
| Limiting speed, oil | 11,000 rpm |
| Weight | 0.345 kg — approx. |
Values from FULI's catalog; confirm for your application.
Nearby 6300 series sizes: 6304 bearing · 6305 bearing · 6307 bearing · 6308 bearing
Grease quantity for 6306: bearing grease fill calculator.
Buying 6306 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 6306 designation
| Segment | Meaning |
|---|---|
| 6 | Single row deep groove ball bearing |
| 3 | Dimension series 03 (medium) |
| 06 | Bore code 06 → 30 mm bore. ISO bore code (00–03 = 10/12/15/17 mm; 04 and above = code × 5 mm). |
6306 cross reference by brand
The basic number 6306 means the same boundary dimensions at every maker listed here (30 × 72 × 19 mm). The suffix for shields, seals and clearance is written differently by each maker.
| Version | FULI | SKF | Timken | NSK | NTN | Koyo | NACHI |
|---|---|---|---|---|---|---|---|
| Open | 6306 | 6306 | 6306 | 6306 | 6306 | 6306 | 6306 |
| Shields both sides | 6306ZZ | 6306-2Z | 6306-ZZ | 6306ZZ | 6306ZZ | 6306 ZZ | 6306ZZE |
| Contact seals both sides | 6306-2RS | 6306-2RS1 | 6306-2RS | 6306DDU | 6306LLU | 6306 2RS | 6306-2NSE |
| Contact seals + C3 | 6306-2RS C3 | 6306-2RS1/C3 | 6306-2RS-C3 | — | — | — | — |
— = ask us. FULI radial clearance is C0 as standard and C3 on request.
SKF cross reference · Timken and Fafnir cross reference · NSK, NTN, Koyo and NACHI cross reference · Suffix meanings
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 6306
FULI makes 6306 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 30 × 72 × 19 mm size.
| Dimension | Nominal, mm | Deviation, µm | Limits, mm |
|---|---|---|---|
| Bore d (Δdmp) | 30 | 0 / −10 | 30.000 / 29.990 |
| Outside diameter D (ΔDmp) | 72 | 0 / −13 | 72.000 / 71.987 |
| Width B (ΔBs) | 19 | 0 / −120 | 19.000 / 18.880 |
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 30 k5 for the shaft of 6306. The housing bore is usually H7, or J7 where the outer ring must not creep.
| Seat | Deviation, µm | Limits, mm | Fit with 6306 |
|---|---|---|---|
| Shaft 30 k5 | +11 / +2 | 30.011 / 30.002 | 2 to 21 µm interference |
| Housing 72 H7 | +30 / 0 | 72.030 / 72.000 | 0 to 43 µm clearance |
| Housing 72 J7 | +18 / −12 | 72.018 / 71.988 | 12 µm interference to 31 µm clearance |
Taking the loosest and the tightest combination of limits, a P0 6306 on a 30 mm k5 shaft has 2 to 21 µm interference. Its outer ring has 0 to 43 µm clearance in an H7 bore and 12 µm interference to 31 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.
6306 compared with nearby sizes
6306 measures 30 × 72 × 19 mm: bore d, outside diameter D and width B. Other deep groove ball bearings on this site for the same 30 mm shaft are 6706 (30 × 37 × 4 mm), 6806 (30 × 42 × 7 mm), 6906 (30 × 47 × 9 mm), 16006 (30 × 55 × 9 mm), 6006 (30 × 55 × 13 mm), 6206 (30 × 62 × 16 mm) and 6406 (30 × 90 × 23 mm).
6406 is the next heavier choice for a 30 mm shaft, with an outside diameter 18 mm larger (90 mm) and 4 mm more width (23 mm). In FULI's catalog 6406 has a dynamic load rating of 43.50 kN against 24.03 kN and a weight of about 0.735 kg against 0.345 kg for 6306.
6206 is the lighter option on the same shaft, with an outside diameter 10 mm smaller (62 mm) and 3 mm less width (16 mm), for housings with less room. In FULI's catalog 6206 has a dynamic load rating of 17.55 kN against 24.03 kN and a weight of about 0.199 kg against 0.345 kg for 6306.
6207 has the same 72 mm outside diameter with a 35 mm bore, so it fits the same housing bore on a larger shaft.
6404 has the same 72 mm outside diameter with a 20 mm bore, so it fits the same housing bore on a smaller shaft.
In the 63 (medium) series the sizes either side of 6306 are 63/28 for a 28 mm shaft and 63/32 for a 32 mm shaft.
| Model | Compared with this page | d × D × B (mm) | Cr (kN) | Weight (kg) |
|---|---|---|---|---|
| 6306 | This page | 30 × 72 × 19 | 24.03 | 0.345 |
| 63/28 | Next size down | 28 × 68 × 18 | 24.03 | 0.287 |
| 63/32 | Next size up | 32 × 75 × 20 | 26.82 | 0.389 |
| 6706 | Same bore | 30 × 37 × 4 | 2.05 | 0.008 |
| 6806 | Same bore | 30 × 42 × 7 | 4.23 | 0.024 |
| 6906 | Same bore | 30 × 47 × 9 | 6.53 | 0.052 |
| 16006 | Same bore | 30 × 55 × 9 | 10.08 | 0.087 |
| 6006 | Same bore | 30 × 55 × 13 | 11.88 | 0.116 |
| 6206 | Same bore | 30 × 62 × 16 | 17.55 | 0.199 |
| 6207 | Same outside diameter | 35 × 72 × 17 | 23.13 | 0.284 |
| 6404 | Same outside diameter | 20 × 72 × 19 | 28.50 | 0.400 |
Cr and weight from FULI's catalog; — = not listed on this site.
6306 weight, load ratings and speed
FULI's catalog gives the weight of 6306 as about 0.345 kg, so 100 bearings weigh about 34.5 kg and 1,000 about 345 kg before packing. The open, ZZ and 2RS versions share this catalog line.
6306 has a dynamic load rating Cr of 24.03 kN and a static load rating C0r of 14.40 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. Limiting speeds in the catalog are 9,500 rpm with grease and 11,000 rpm with oil.
Contact seals add friction at the lip, so 6306-2RS usually runs below the speed of the open bearing. Ask us for the limit of the version you order.
Values from FULI's catalog; confirm for your application.
6306 versions: open, ZZ, 2RS and C3
Every version of 6306 has the same 30 × 72 × 19 mm boundary dimensions; only the cover between the rings and the internal clearance change. FULI supplies open, ZZ and 2RS versions, with C0 clearance as standard and C3 on request. Other makers write the same covers as 2Z or ZZ for shields and 2RS1, DDU or LLU for contact seals.
| Designation | What it is | Typical choice |
|---|---|---|
| 6306 | Open, no shields or seals | Housings with their own oil or grease supply |
| 6306-ZZ | Two metal shields, non-contact, greased | Motors and fans where dust is light |
| 6306-2RS | Two rubber contact seals, greased | Pumps, farm machinery and other wet or dusty places |
| 6306-ZZ C3 | ZZ with the larger C3 radial clearance | Tight shaft fit or a housing that runs hot |
| 6306-2RS C3 | 2RS with C3 radial clearance | Sealed bearings on a tight fit or running hot |
6306 dimensions in inches
The nearest common inch shaft size to the 30 mm bore of 6306 is 1-3/16 in (30.16 mm), 0.16 mm larger than the bore, so 6306 will not go on it. Inch shafts need an inch bearing, not a metric one with a sleeve or shim.
| Dimension | Millimetres | Inches |
|---|---|---|
| Bore d | 30 mm | 1.1811 in |
| Outside diameter D | 72 mm | 2.8346 in |
| Width B | 19 mm | 0.7480 in |
Converted at 1 in = 25.4 mm and rounded to four decimals. The bearing itself is made to the millimetre sizes.
Grease for 6306
FULI fills sealed 6306-2RS and 6306-ZZ bearings to about 30% of the free internal space as standard. The fill is set on an automatic greasing machine after sample sets are weighed before and after greasing. In normal use, sealed bearings usually do not need regreasing. A different fill level, a low-noise grease or a grease for a stated temperature range can be written on the order; for North America a range of −40 to 120 °C is often asked for.
Relubricating 6306 from the side takes about 6.84 g each time by the formula in our grease calculator: 0.005 × D × B = 0.005 × 72 × 19. This applies to the open 6306 in a housing with a grease supply.
How FULI supplies 6306
The standard 6306 from FULI has GCr15 chrome steel rings and balls, P0 precision, C0 radial clearance and vibration grade Z3V3; P6, C3 and other vibration grades are made on request. Radial clearance is set on automatic assembly equipment and sampled during production. Orders with a noise or vibration requirement are tested set by set before packing.
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 6306-2RS C3.
Tools and guides for 6306
- Bearing size finder: look up a size from bore, OD and width
- Bearing weight chart
- Bearing grease fill calculator
- Shaft and housing tolerance chart
- Open, ZZ or 2RS seal selector
- Bearing internal clearance: C0, C3 and when to change
- Bearing lubrication basics
- Noise grade and precision class
- Ball bearing vs roller bearing
- All bearing products and model pages
Typical applications
- Electric motors
- Fans and blowers
- Water pumps
- Gearboxes
- Agricultural and textile machinery
FAQ
What is the difference between 6306 and 6406?
Both fit a 30 mm shaft. 6306 is 30 × 72 × 19 mm and 6406 is 30 × 90 × 23 mm, so 6406 has an outside diameter 18 mm larger (90 mm) and 4 mm more width (23 mm). In FULI's catalog 6406 has a dynamic load rating of 43.50 kN against 24.03 kN and a weight of about 0.735 kg against 0.345 kg for 6306. Choose 6406 for a higher load where the housing has room for it; 6306 keeps the housing smaller.
What is the difference between 6306 and 6206?
Both fit a 30 mm shaft. 6306 is 30 × 72 × 19 mm and 6206 is 30 × 62 × 16 mm, so 6206 has an outside diameter 10 mm smaller (62 mm) and 3 mm less width (16 mm). In FULI's catalog 6206 has a dynamic load rating of 17.55 kN against 24.03 kN and a weight of about 0.199 kg against 0.345 kg for 6306. 6206 suits a housing with less room; 6306 carries more load.
What size is 6306 in inches?
6306 is 1.1811 × 2.8346 × 0.7480 in (30 × 72 × 19 mm, d × D × B). The nearest common inch shaft size to the 30 mm bore of 6306 is 1-3/16 in (30.16 mm), 0.16 mm larger than the bore, so 6306 will not go on it. Use an inch bearing on an inch shaft.
How much does 6306 weigh?
About 0.345 kg in FULI's catalog, so 100 pieces weigh about 34.5 kg before packing. The open, ZZ and 2RS versions share this catalog line.
What is the difference between 6306-ZZ and 6306-2RS?
Both are 30 × 72 × 19 mm, the same as the open 6306. 6306-ZZ has two metal shields that do not touch the inner ring, so it runs with little drag but only keeps out coarse dirt. 6306-2RS has two rubber seals whose lips touch the inner ring; it keeps out water and fine dust at the cost of more friction. FULI fills both to about 30% of the free space.
How much grease does 6306 need?
Sealed 6306-2RS and 6306-ZZ come filled to about 30% of the free space and in normal use usually do not need regreasing. An open 6306 relubricated from the side takes about 6.84 g each time (0.005 × 72 × 19).
Is 6306 the same size across brands?
Yes. 6306 is an ISO designation, so the bore, outside diameter and width are the same whichever manufacturer made it. Brand-specific suffixes only change details such as seals, clearance or cage.