30304 bearing: complete specifications & equivalents
The 30304 is a ISO 355 radial bearing sized 20 x 52 x 16.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 20 mm |
| Outer diameter D | 52 mm |
| Width B | 16.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 41.9 kN |
| Basic static load rating C0 | 32.5 kN |
| Fatigue load limit Pu | 3.55 kN |
| Reference speed (thermal) | 12000 rpm |
| Limiting speed (mechanical) | 14000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 170 g |
| Manufacturer designation | SKF 30304 |
| 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 | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.64 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 16 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) | 3 of 32 |
| Bore above smallest 30300-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30304 | 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. |
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 30304 model number is decoded
Ordering number SKF 30304 in SKF catalogue PUB BU/P1 17000 denotes a single-row tapered roller bearing for a 20 mm shaft, heavy-OD section, with an open pressed-steel-cage execution and one-direction axial capacity.Numbering ties the bearing to its envelope: 30304 means tapered-roller type 3, heavy-OD section series 03, 20 mm bore — which is why the 52×16.25 mm outline swaps dimensionally with other ISO 355 bearings of the same code. 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. Catalogue mass 170 g for the 20×52×16.25 mm open execution covers the pressed-steel cage and standard roller complement; sealed or special-clearance variants differ slightly in mass and carry their own order numbers. Specify pairs rather than single units wherever thrust reverses: the tapered contact of 30304 generates an induced axial load under radial force, and an unpaired bearing on a reversing shaft will run slack and fret its seat.
Typical equipment & failure modes
Common applications
- agricultural implement hubs
- small conveyor drive pulleys
- power-tool gear heads
- small automotive wheel hubs and trailer axles
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
- preload loss as the mounted pair relaxes, letting rollers skid and smear the raceways
- axial overload spalling at the roller-rib contact beyond the single-row thrust rating
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- grease degradation after long shelf storage without rotation or re-greasing
Selection pitfalls — read before you substitute
- At a 20 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 30304 shows up as gearbox vibration long before it fails.
- The 303 series at 20 mm bore (52×16.25 mm) carries a larger OD and higher capacity than 30204 at the same bore; the bigger section runs hotter, so re-check the 14,000 r/min speed ceiling and shoulder diameters before substituting.
- At the 41.9 kN rating of 30304, preload class changes stiffness by tens of percent but also heat generation; select light preload for the 14,000 r/min speed end and heavier preload only where moment stiffness dominates.
- Do not mix brands or executions inside one 30304 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.
- Catalogue reference speed and limiting speed are different limits: the 12,000 r/min reference is a thermal criterion under load, while the 14,000 r/min limiting value is the mechanical ceiling — observe both.
- The 41.9/32.5 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 30304 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30304 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 30304?
The SKF 30304 is a single-row tapered roller bearing with 20 mm bore, 52 mm outer diameter and 16.25 mm width (0.787 × 2.047 × 0.64 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 41.9 kN, C0 32.5 kN, fatigue load limit Pu 3.55 kN, reference speed 12,000 r/min, limiting speed 14,000 r/min, mass about 170 g. It is an open, separable bearing with a pressed-steel cage.
How does the 30304 bore code work?
The last two digits of 30304 are bore code 04, so 04 × 5 = 20 mm bore. The 52 mm OD and 16.25 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 30304 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 30304 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 30304 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 30304 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.