7321 bearing: complete specifications & equivalents
The 7321 is a ISO 15 radial bearing sized 105 x 225 x 49 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 | 49 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 203 kN |
| Basic static load rating C0 | 193 kN |
| Fatigue load limit Pu | 6.4 kN |
| Reference speed (thermal) | 3600 rpm |
| Limiting speed (mechanical) | 3400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 8550 g |
| Manufacturer designation | SKF 7321 BEP |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 3.1 single-row ACBB |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 3.1 single-row ACBB) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 3.1 single-row ACBB); 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 & 7300-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 8.858 in |
| Width B | 1.929 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 60 mm |
| Smallest bore in 7300-series | 10 mm |
| Largest outer diameter in 7300-series | 420 mm |
| Width range across 7300-series | 11–80 mm |
| Bore position in 7300-series (smallest first) | 22 of 32 |
| Bore above smallest 7300-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7321-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×225×49 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
| 6321 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Identical envelope but a different bearing type — confirm load and speed suitability before substitution. |
| 6321-ZZ | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | Identical envelope but a different bearing type — confirm load and speed suitability before substitution. |
| 7321-BEP | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 7321 BEP (glass-fibre PA66 cage, open arrangement) is the same-envelope execution with ratings within 10 % — boundary dimensions interchangeable. |
| 7321-BECBP | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 7321 BECBP (glass-fibre PA66 cage, open arrangement) is the same-envelope execution with ratings within 10 % — boundary dimensions interchangeable. |
| 7321-DECBM | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 7321 DECBM (brass cage, open arrangement) is the same-envelope execution with ratings within 10 % — boundary dimensions interchangeable. |
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 7321 model number is decoded
Ordering number 7321 BEP in the SKF Rolling Bearings catalogue denotes a single-row 40° angular-contact ball bearing for a 105 mm shaft, medium (7300) series, with an open PA66-caged execution and one-direction axial capacity.Reading the designation: the leading 7 marks a single-row angular-contact ball bearing, the 3 is ISO diameter series 3 (medium section), and the last two digits encode the 105 mm bore; the 225 mm OD and 49 mm width follow the ISO 15 general plan. In SKF suffix language B sets the steep 40° angle for high axial capacity, E is the optimised internal design, and P is the polymer cage; variants with seals (BE-2RZP), 25° angles (A/ACC) or brass cages (BECBM) are separate order numbers. Selection arithmetic: the C0/C ratio is about 0.95 (static 193 kN against dynamic 203 kN), typical of a 40° angle sized for axial capacity, and the 6.4 kN fatigue load limit Pu is the equivalent-load floor used in the SKF life calculation. Fit selection follows the rotating ring — interference on a rotating inner ring — and two 7321 units are required to take reversing thrust; keep the induced axial load (0.5·Fr/Y for the 40° angle) inside the rated capacity when calculating the pair.
Typical equipment & failure modes
Common applications
- heavy industrial gearboxes
- large process pumps and compressors
- marine propulsion and deck machinery
- wind-turbine gearbox shafts
Known failure patterns
- contamination wear through the open arrangement when no external seal is provided
- raceway smearing under marginal lubrication at start-up before oil reaches the contact ellipse
- fretting at the ground set faces of a pair whose clamp torque relaxes in service
- thermal preload runaway in a back-to-back pair when inner-ring heat has nowhere to expand
- PA66 cage embrittlement after sustained running above its 120 °C continuous-temperature ceiling
- edge loading from shaft deflection or housing misalignment
Selection pitfalls — read before you substitute
- At 105 mm bore the ring mass is high enough that cocking during mounting damages the cage and race lips; guide the ring square, confirm seat contact around the full circumference, and re-check preload after the first thermal cycle of the paired set.
- The 73xx medium section at 105 mm bore (225×49 mm) is heavier-rated than the 7221 but runs hotter at the same speed; do not substitute a 7321 into a 72-series spindle position without re-checking dn, lubricant film and preload.
- DB (back-to-back) pairs are stiffer against moments, DF (face-to-face) pairs tolerate misalignment and thermal growth better; choosing the arrangement from the 2D drawing rather than the actual shaft thermal expansion is a common 7321 mounting error.
- The 40° contact angle creates an induced axial load under pure radial force; include it in the 7321 rating calculation (and account for it in both bearings of a pair) or the unloaded bearing skids its balls.
- Open 7321 units need application-supplied sealing and a defined lubricant supply; in oil lubrication keep the oil level below the lowest rolling element or churning raises temperature well beyond the catalogue speed figures.
- The 203/193 kN ratings are SKF catalogue 17000 values for the 7321 BEP 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 7321 (BEP basic, BECBP universally matchable, BE-2RZP sealed, BECBM brass-cage, ACC-series at 25°); they are not interchangeable order numbers — quote the full 7321 BEP designation when purchasing and match the execution to the mounting arrangement.
- A plain 7321 BEP is a single open bearing, not a universally matchable one; to mount a defined DB/DF pair order the BECBP (CB) execution — pairing two unmatched basic units gives uncontrolled preload because the side faces are not ground for set mounting.
Frequently asked questions
What are the dimensions and catalogue data of SKF 7321?
The SKF 7321 BEP is a single-row angular-contact ball bearing with 105 mm bore, 225 mm outer diameter and 49 mm width (4.134 × 8.858 × 1.929 in) per ISO 15. From SKF catalogue 17000: basic dynamic load rating C 203 kN, C0 193 kN, fatigue load limit Pu 6.4 kN, reference speed 3,600 r/min, limiting speed 3,400 r/min, mass about 8550 g. It is an open 40° contact-angle bearing with a PA66 cage. The two speed figures are independent limits and the operating point must clear both.
How does the 7321 bore code work?
The last two digits of 7321 are bore code 21, so 21 × 5 = 105 mm bore. The 225 mm OD and 49 mm width come from the ISO 15 diameter-series plan, shared with the 6321 deep-groove envelope.
What do the 73xx and BEP designations mean?
The leading 7 marks a single-row angular-contact bearing; the second digit 3 is the ISO diameter series (medium section). In the SKF suffix, B denotes the 40° contact angle, E the enhanced internal design, P the glass-fibre PA66 cage. The plain BEP is the basic open single bearing; BECBP is the universally matchable version. A 25° variant (suffix A, e.g. ACC) runs faster but carries less thrust.
Can a single 7321 take axial load in both directions?
No — one single-row angular-contact bearing reacts thrust in one direction only, and under radial load its 40° contact angle induces an axial force. Use two bearings as a matched pair: DB (back-to-back) for a rigid, moment-resisting arrangement, DF (face-to-face) where thermal expansion must be tolerated, or DT (tandem) where one-direction thrust is shared. Universally matchable CB executions can be assembled into pairs directly; define the preload class against the load and speed of the position.
How does 7321 compare with a deep-groove 6321?
Both use the 105×225×49 mm ISO 15 envelope, but the angular-contact 7321 has an asymmetric raceway at a nominal 40° angle: higher combined axial-plus-radial capacity and controlled preload, at the cost of speed, one-direction thrust, mandatory pairing for reversing loads and a minimum axial load requirement. A 6321 cannot be dropped into a combined-load 7321 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. 3.1 single-row ACBB on 2026-09-26. Read our editorial & correction policy.