6306 bearing: complete specifications & equivalents
The 6306 is a ISO 15 radial bearing sized 30 x 72 x 19 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 30 mm |
| Outer diameter D | 72 mm |
| Width B | 19 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 29.6 kN |
| Basic static load rating C0 | 16 kN |
| Fatigue load limit Pu | 0.67 kN |
| Reference speed (thermal) | 20000 rpm |
| Limiting speed (mechanical) | 13000 rpm |
| Operating temperature | -40 to +150 °C |
| Mass | 350 g |
| Manufacturer designation | SKF 6306 |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-25 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-24
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & 6300-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 0.748 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 21 mm |
| Smallest bore in 6300-series | 2 mm |
| Largest outer diameter in 6300-series | 500 mm |
| Width range across 6300-series | 3–95 mm |
| Bore position in 6300-series (smallest first) | 13 of 40 |
| Bore above smallest 6300-series size | 28 mm |
Mounting, lubrication & life for 6306
Recommended fits & mounting
- Rotating inner ring on a 30 mm shaft: k5; housing bore H7 for normal stationary-load outer rings. Reverse the logic if the outer ring rotates.
- Fit by induction heating (max 120 °C) where practical — never drive the ring home through the rolling elements.
- Keep shaft and housing fillet radii below the bearing chamfer so the 19 mm-wide ring seats square on its shoulder.
Lubrication strategy
Open execution: the application supplies lubrication. Use the grease relubrication chart for this bearing — pitch diameter dm = 51 mm, so the speed factor at the 13,000 r/min limiting speed is 663,000 mm·r/min. Intervals shorten steeply as that factor rises.
Worked L10 life example (illustrative duty)
For ball bearings, L10h = (C/P)3 · 106 / (60·n). Taking an example radial equivalent load P = 3 kN at n = 1,500 r/min (a small belted motor duty — substitute the real equivalent load from the application calculation):
C = 29.6 kN → L10h ≈ 10,673 hours
Choosing a section at the same 30 mm bore
| Series | Open execution | OD × width | C (kN) | Limiting speed (r/min) |
|---|---|---|---|---|
| 60xx | 6006-FAG | 55 × 13 | 14.5 | 20,100 |
| 62xx | 6206-FAG | 62 × 16 | 22.0 | 17,800 |
| 63xx | 6306-FAG | 72 × 19 | 32.0 | 15,100 |
| 64xx | 6406-FAG | 90 × 23 | 42.5 | 11,000 |
| 618xx | 61806-FAG | 42 × 7 | 4.5 | 24,500 |
| 619xx | 61906-FAG | 47 × 9 | 7.2 | 21,700 |
| 160xx | 16006 | 55 × 9 | 11.2 | 18,500 |
A larger section is not a drop-in swap — OD and width change — and same-envelope seal variants are compared on the 30×72×19 envelope page. Match meaning, not the size chart alone: see what the cross-reference levels mean.
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6306-2RS-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6306-FAG | FAG | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 6306-ZZ-FAG | FAG | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 6306 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; standard interchange — confirm clearance class and precision with the supplier. |
| 6306-2RS-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6306-NSK | NSK | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 6306-RSR-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs RSR) — confirm sealing suits the duty. |
| 6306-ZZ-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 6306-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs 2RS) — confirm sealing suits the duty. |
| 6306-NTN | NTN | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
| 6306-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs RSR) — confirm sealing suits the duty. |
| 6306-ZZ-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×72×19 mm envelope per ISO 15; seal variant differs (OPEN vs ZZ) — confirm sealing suits the duty. |
| 7306 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| NU306 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
| 1726306-2RS1 | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 1726306-2RS1 is a standard-inner-ring insert on the same 30x72x19 mm ISO 15 envelope with ratings within 10 %, but its outer surface is sphered for a Y-housing whereas this page is the cylindrical-OD deep-groove bearing — not interchangeable mounts. |
| W6306-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 6306-2RS1 shares the 30×72×19 mm envelope but rates differently (29.6/16 kN vs 22.9/15 kN) — not a load-rating equivalent. |
| W6306-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 6306-2Z shares the 30×72×19 mm envelope but rates differently (29.6/16 kN vs 22.9/15 kN) — not a load-rating equivalent. |
| W6306 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF stainless execution W 6306 shares the 30×72×19 mm envelope but rates differently (29.6/16 kN vs 22.9/15 kN) — not a load-rating equivalent. |
| 306 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 306 shares the 30×72×19 mm envelope but catalogue C/C0 differ — envelope match only after a load check. |
| 306-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF 306-2Z shares the 30×72×19 mm envelope but catalogue C/C0 differ — envelope match only after a load check. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 6306 model number is decoded
6306 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the medium 63xx section (diameter series 3 of ISO 15), multiplying bore code 06 by five gives the 30 mm bore; the 72 mm outside diameter and 19 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 30 mm shaft under normal load, catalogue practice seats it on a k5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. In the SKF catalogue this open execution carries the bare designation; protected variants are ordered separately as -2Z and -2RSH.
Typical equipment & failure modes
Common applications
- agricultural equipment
- fans and blowers
- electric motors
- centrifugal pumps
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- brinelling from static overload or hammering during mounting
- false brinelling from vibration while the shaft is stationary
Selection pitfalls — read before you substitute
- A 30 mm shaft for 6306 should be finished to Ra ≤ 1.6 µm with square seating faces; at this bore a scored or oval journal shows up directly as running noise and early raceway damage.
- The 63xx medium section at 30 mm bore gains dynamic rating through larger rolling elements on a 72 mm OD; the penalty is mass and a lower limiting speed than the 6206 — do not specify it for speed-critical shafts.
- The open 6306 has no lubricant retention: grease escapes and contaminants migrate straight into the 30×72×19 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Open bearings tolerate the highest speeds in the 6300-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 6306 units.
- Vibration during standstill brinells the raceways of a 30 mm bearing at ball spacing; if the machine sits idle next to running equipment, turn the shaft over periodically or isolate the arrangement.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 72 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6306.
- The open 6306 needs external sealing and application-supplied lubrication; in the SKF catalogue the protected variants are separate order numbers 6306-2Z (shields) and 6306-2RSH (contact seals), not suffix-free 6306.
- The 29.6/16 kN ratings here are SKF Explorer-class figures from catalogue PUB BU/P1 17000/1 EN (Oct 2018); SKF can revise internal geometry and ratings without changing the designation, so treat the catalogue version and date as part of the specification and re-verify for critical drives.
Frequently asked questions
What are the dimensions of a 6306 bearing?
A 6306 deep-groove ball bearing has a 30 mm bore, 72 mm outer diameter and 19 mm width (1.181 × 2.835 × 0.748 in), per ISO 15 boundary dimensions. It is an open bearing with no seals or shields.
What lubrication does 6306 need?
The open 6306 is lubricated by the application; a NLGI 2 lithium-soap grease filled to roughly 25–35% of the free volume is the common choice, with a defined relubrication interval.
How does the 6306 bore code work?
The last two digits of 6306 are bore code 06, giving 06 × 5 = 30 mm bore. The 72 mm outside diameter and 19 mm width follow the ISO 15 diameter series, not the bore code alone.
What does no suffix on 6306 mean?
A bare 6306 designation means open: no shields or seals, normal CN radial clearance and P0 normal tolerance unless further suffixes are ordered. The application must supply and retain the lubrication.
What is the SKF designation and catalogue data for 6306?
In the SKF Rolling Bearings catalogue this size is listed as 6306 — the open (unsealed) execution, 30×72×19 mm per ISO 15. Quoted values: C 29.6 kN, C0 16 kN, Pu 0.67 kN, limiting speed 13000 r/min, mass 350 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6306.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-25. Read our editorial & correction policy.