30303 bearing: complete specifications & equivalents
The 30303 is a ISO 355 radial bearing sized 17 x 47 x 15.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 17 mm |
| Outer diameter D | 47 mm |
| Width B | 15.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 34.2 kN |
| Basic static load rating C0 | 25 kN |
| Fatigue load limit Pu | 2.7 kN |
| Reference speed (thermal) | 13000 rpm |
| Limiting speed (mechanical) | 16000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 130 g |
| Manufacturer designation | SKF 30303 |
| 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 | 0.669 in |
|---|---|
| Outer diameter D | 1.85 in |
| Width B | 0.6 in |
| ISO bore code | 03 |
| Radial section height (D−d)/2 | 15 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) | 2 of 32 |
| Bore above smallest 30300-series size | 2 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30303 | 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. |
| 30303-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 30303 model number is decoded
SKF 30303 (SKF 30303) is the heavy-OD section tapered roller choice for a 17 mm shaft — one row of tapered rollers on an asymmetric raceway inside the 47×15.25 mm ISO 355 envelope.Digit by digit, 30303 reads as bearing type 3 (single-row tapered roller), heavy-OD section series 03, and bore reference 03 resolving to 17 mm; 47 mm OD and 15.25 mm width are the matching ISO 355 boundary values. 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. The 15.0 mm radial section height ((47−17)/2) and 130 g catalogue mass frame a 17 mm bore bearing rated at 34.2 kN C — roughly 2.01 kN of dynamic capacity per millimetre of bore before application factors. Note the minimum-axial-load requirement: at light radial load and high speed the rollers of 30303 must still be held into the rib contact, which is another reason the catalogue recommends paired mounting with controlled setting.
Typical equipment & failure modes
Common applications
- electric-motor pinion shafts
- steering knuckles and small differentials
- agricultural implement hubs
- small conveyor drive pulleys
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
- roller large-end smearing against the cone rib after EP lubricant film failure
- false brinelling on idle paired sets exposed to machine vibration
- cage pocket scoring when the bearing starts cold with grease of too-high base-oil viscosity
- rolling-contact fatigue spalling after the rated L10 life is exceeded
Selection pitfalls — read before you substitute
- At a 17 mm bore the thin cone and cup are easily distorted by an over-tight shaft nut; check seat runout (target Ra ≤ 0.8 µm) and torque the locknut progressively — a pinched 30303 shows up as gearbox vibration long before it fails.
- The 303 series at 17 mm bore (47×15.25 mm) carries a larger OD and higher capacity than 30203 at the same bore; the bigger section runs hotter, so re-check the 16,000 r/min speed ceiling and shoulder diameters before substituting.
- A single 30303 cannot locate the shaft axially in both directions; mounting it singly on a reversing-thrust shaft leaves one direction uncontrolled — always use an O or X matched pair for bidirectional location.
- When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 30303 pushes the rings apart under load, so a non-located cup walks its seat even when the shaft is fixed.
- Shaft and housing fillets must clear the bearing chamfer so the 15.25 mm-wide cup seats square; use an undercut or withdrawal groove rather than an oversized radius that locks on the ring face.
- The 34.2/25 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 30303 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30303 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 30303?
The SKF 30303 is a single-row tapered roller bearing with 17 mm bore, 47 mm outer diameter and 15.25 mm width (0.669 × 1.85 × 0.6 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 34.2 kN, C0 25 kN, fatigue load limit Pu 2.7 kN, reference speed 13,000 r/min, limiting speed 16,000 r/min, mass about 130 g. It is an open, separable bearing with a pressed-steel cage.
How does the 30303 bore code work?
The last two digits of 30303 are bore code 03, one of the small special codes: 00 = 10 mm, 01 = 12 mm, 02 = 15 mm, 03 = 17 mm — here 03 = 17 mm bore. The 47 mm OD and 15.25 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 30303 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 30303 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 30303 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 30303 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.