30321 bearing: complete specifications & equivalents
The 30321 is a ISO 355 radial bearing sized 105 x 225 x 53.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 105 mm |
| Outer diameter D | 225 mm |
| Width B | 53.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 462 kN |
| Basic static load rating C0 | 530 kN |
| Fatigue load limit Pu | 57 kN |
| Reference speed (thermal) | 2200 rpm |
| Limiting speed (mechanical) | 3000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 9100 g |
| Manufacturer designation | SKF 30321 |
| 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 | 4.134 in |
|---|---|
| Outer diameter D | 8.858 in |
| Width B | 2.106 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 60 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) | 20 of 32 |
| Bore above smallest 30300-series size | 90 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30321 | 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 30321 model number is decoded
In SKF catalogue PUB BU/P1 17000, 30321 appears as SKF 30321: an open, single-row tapered roller bearing in the heavy-OD section of the 30300 dimension series, supplied with a pressed-steel cage as standard.On the SKF nameplate, 30321 follows the ISO 355 convention: 3 for the tapered-roller type, 03 for the heavy-OD section, final digits 21 for the 105 mm bore. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. 2GB); it is the dimensional series, not a separate part number. Selection arithmetic: the C0/C ratio is about 1.15 (static 530 kN against dynamic 462 kN), typical of a tapered roller sized for axial capacity, and the 57 kN fatigue load limit Pu is the equivalent-load floor used in the life calculation. For a 105 mm shaft the usual cone seat is m6 with an H7 housing when the inner ring rotates; arrange two 30321 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
- heavy industrial gearboxes and speed reducers
- large process pump and compressor shafts
- rolling-mill auxiliary drives
- crane sheave and hoist gearboxes
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
- rib-roller contact scoring from loss of the EP additive film
Selection pitfalls — read before you substitute
- Mount the 105 mm bore 30321 by induction heating of the cone (max 120 °C — the pressed-steel cage sets the ceiling, not the steel); driving it home through the cup or rollers brinells the tapered raceway.
- The 303 series at 105 mm bore (225×53.5 mm) carries a larger OD and higher capacity than 30221 at the same bore; the bigger section runs hotter, so re-check the 3,000 r/min speed ceiling and shoulder diameters before substituting.
- When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 30321 pushes the rings apart under load, so a non-located cup walks its seat even when the shaft is fixed.
- When the outer ring rotates, reverse the fit logic and provide cup location; the tapered contact of 30321 pushes the rings apart under load, so a non-located cup walks its seat even when the shaft is fixed.
- Catalogue reference speed and limiting speed are different limits: the 2,200 r/min reference is a thermal criterion under load, while the 3,000 r/min limiting value is the mechanical ceiling — observe both.
- The 462/530 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 30321 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30321 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 30321?
The SKF 30321 is a single-row tapered roller bearing with 105 mm bore, 225 mm outer diameter and 53.5 mm width (4.134 × 8.858 × 2.106 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 462 kN, C0 530 kN, fatigue load limit Pu 57 kN, reference speed 2,200 r/min, limiting speed 3,000 r/min, mass about 9100 g. It is an open, separable bearing with a pressed-steel cage.
How does the 30321 bore code work?
The last two digits of 30321 are bore code 21, so 21 × 5 = 105 mm bore. The 225 mm OD and 53.5 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 30321 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 30321 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 30321 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 30321 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.