30306 bearing: complete specifications & equivalents
The 30306 is a ISO 355 radial bearing sized 30 x 72 x 20.75 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 | 20.75 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 69.2 kN |
| Basic static load rating C0 | 56 kN |
| Fatigue load limit Pu | 6.4 kN |
| Reference speed (thermal) | 8000 rpm |
| Limiting speed (mechanical) | 10000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 380 g |
| Manufacturer designation | SKF 30306 |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB); 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 & 30300-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 0.817 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 21 mm |
| Smallest bore in 30300-series | 15 mm |
| Largest outer diameter in 30300-series | 500 mm |
| Width range across 30300-series | 14.25–105 mm |
| Bore position in 30300-series (smallest first) | 5 of 32 |
| Bore above smallest 30300-series size | 15 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30306 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 355 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
| 30306-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. |
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 30306 model number is decoded
The SKF 30306 is a 30×72×20.75 mm single-row tapered roller bearing — the heavy-OD section entry in the 30300 series, with an asymmetric raceway cut for thrust capacity and separable mounting.The code breaks down as type prefix 3 (tapered roller), series 03 (the heavy-OD section), and bore code 06 = 30 mm; dimensions 30×72×20.75 mm therefore match the ISO 355 envelope. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. 2FB); it is the dimensional series, not a separate part number. Speed planning uses two different ceilings: 8,000 r/min thermal reference and 10,000 r/min mechanical limiting speed. For a 30 mm shaft the usual cone seat is k5 with an H7 housing when the inner ring rotates; arrange two 30306 bearings as a set for two-direction location and set clearance from the load diagram, never from assembly feel.
Typical equipment & failure modes
Common applications
- industrial gearbox shafts and reducers
- differential and pinion drives
- pump and compressor shafts
- machine-tool spindles
Known failure patterns
- cup or cone misalignment when the separable rings are not seated square during mounting
- loose cup rotation in the housing when the specified press fit is not achieved
- false brinelling on idle paired sets exposed to machine vibration
- roller large-end smearing against the cone rib after EP lubricant film failure
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- rib-roller contact scoring from loss of the EP additive film
Selection pitfalls — read before you substitute
- On this 30 mm bore, interference and temperature rise consume clearance inside a preloaded pair; calculate the residual clearance after mounting and at operating temperature — an over-tight 30306 pair heats, loses setting control and smears the roller-rib contact.
- The 303 series at 30 mm bore (72×20.75 mm) carries a larger OD and higher capacity than 30206 at the same bore; the bigger section runs hotter, so re-check the 10,000 r/min speed ceiling and shoulder diameters before substituting.
- Do not mix brands or executions inside one 30306 pair — matched sets are ground for a specific setting, and pairing a SKF basic unit with a different suffix variant will not share the setting evenly.
- The tapered contact angle creates an induced axial load under pure radial force; include it in the 30306 rating calculation (and account for it in both bearings of a pair) or the unloaded bearing skids its rollers.
- Never press both rings through the wrong element during fitting: force for an interference shaft seat goes through the cone only, or brinell marks on the 72 mm cup race release as noise within the first running hours.
- The 69.2/56 kN ratings are SKF catalogue 17000 values for the basic execution; SKF can revise internal geometry without changing the order number, so keep the catalogue version (PUB BU/P1 17000/1 EN, 2018) with the specification and re-verify for critical drives.
- SKF lists several executions of 30306 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30306 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 30306?
The SKF 30306 is a single-row tapered roller bearing with 30 mm bore, 72 mm outer diameter and 20.75 mm width (1.181 × 2.835 × 0.817 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 69.2 kN, C0 56 kN, fatigue load limit Pu 6.4 kN, reference speed 8,000 r/min, limiting speed 10,000 r/min, mass about 380 g. It is an open, separable bearing with a pressed-steel cage.
How does the 30306 bore code work?
The last two digits of 30306 are bore code 06, so 06 × 5 = 30 mm bore. The 72 mm OD and 20.75 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 30306 series and basic execution designations mean?
The leading 3 marks a single-row tapered roller bearing; the second digit 03 is the ISO 355 series (heavy-OD section). The SKF catalogue lists the ISO 355 dimension-series code after the bare number. A steeper-contact-angle variant (B suffix) is a different order number and is not interchangeable with the basic execution.
Can a single 30306 take axial load in both directions?
No — one single-row tapered roller bearing reacts thrust in one direction only, and under radial load its contact angle induces an axial force. Use two bearings as a matched pair: O (back-to-back) for a rigid, moment-resisting arrangement, X (face-to-face) where thermal expansion must be tolerated, or tandem where one-direction thrust is shared.
How does 30306 compare with a ball bearing of the same bore?
A tapered roller bearing has line contact and a steep contact angle: much higher combined axial-plus-radial capacity and shock resistance than a ball bearing of the same bore, at the cost of speed, one-direction thrust, mandatory pairing for reversing loads and a minimum axial load requirement. A ball bearing cannot be dropped into a combined-load 30306 position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB on 2026-09-26. Read our editorial & correction policy.