7221 bearing: complete specifications & equivalents
The 7221 is a ISO 15 radial bearing sized 105 x 190 x 36 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 | 190 mm |
| Width B | 36 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 156 kN |
| Basic static load rating C0 | 150 kN |
| Fatigue load limit Pu | 5.2 kN |
| Reference speed (thermal) | 4000 rpm |
| Limiting speed (mechanical) | 4300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3950 g |
| Manufacturer designation | SKF 7221 BECBP |
| 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 & 7200-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.417 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 42.5 mm |
| Smallest bore in 7200-series | 10 mm |
| Largest outer diameter in 7200-series | 540 mm |
| Width range across 7200-series | 9–85 mm |
| Bore position in 7200-series (smallest first) | 22 of 36 |
| Bore above smallest 7200-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7221-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. |
| 6221 | 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. |
| 6221-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. |
| 7221-BECBP | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 7221 BECBP (glass-fibre PA66 cage, open arrangement) is the same-envelope execution with ratings within 10 % — boundary dimensions interchangeable. |
| 7221-BECBM | SKF | full Dimensions and internal design equivalent — standard interchange. | SKF 7221 BECBM (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 7221 model number is decoded
For a 105 mm shaft carrying combined load, SKF lists 7221 under catalogue execution 7221 BECBP: one open single-row angular-contact ball bearing, 40° contact angle, in the light (7200) series of the 7xxx family.Digit by digit, 7221 reads as bearing type 7 (single-row angular contact), light section diameter series 2, and bore reference 21 resolving to 105 mm; 190 mm OD and 36 width are the matching ISO 15 boundary values. Here B marks the steep 40° contact angle (the highest-capacity single-row angle), E the modernised internal geometry and P the glass-fibre nylon cage; the same bare size in a 25° A-angle or brass M-cage execution carries a different suffix. As a CB execution the rings are delivered match-ready: face-to-face or back-to-back pairs can be assembled without regrinding, and Normal (CB) clearance suits general preloaded pairs — GA/GB/GC suffixes would denote factory-set light/medium preload. Speed planning uses two different ceilings: 4,000 r/min reference (thermal, under representative load) and 4,300 r/min limiting (mechanical cage/ball limit). Fit selection follows the rotating ring — interference on a rotating inner ring — and two 7221 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
- large process pumps and compressors
- marine propulsion and deck machinery
- wind-turbine gearbox shafts
- rolling-mill auxiliary drives
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
- ball skidding when the induced axial load unloads the inactive bearing of a pair
- raceway spalling from axial overload beyond the single-direction thrust rating
- cage pocket damage when the bearing is started cold with grease of too-high base-oil viscosity
- mounting score marks when the bearing is cocked over the shaft keyway or a burr
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 72xx light section at 105 mm bore is the general-purpose angular-contact envelope (190×36 mm); stepping up to a 7321 changes OD, width and heat generation — it is not a drop-in swap when the housing and speed are fixed.
- A single 7221 cannot locate the shaft axially in both directions; mounting it singly on a reversing-thrust shaft leaves one direction uncontrolled — always use a DB or DF matched pair for bidirectional location.
- 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 7221 mounting error.
- Never press both rings through the wrong element during fitting: force for an interference shaft seat goes through the inner ring only, or brinell marks on the 190 mm race release as noise within the first running hours.
- The 156/150 kN ratings are SKF catalogue 17000 values for the 7221 BECBP 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 7221 (BEP basic, BECBP universally matchable, BE-2RZP sealed, BECBM brass-cage, ACC-series at 25°); they are not interchangeable order numbers — quote the full 7221 BECBP designation when purchasing and match the execution to the mounting arrangement.
- The CB execution (7221 BECBP) ships prepared for pair mounting but is not a matched set by itself: preload results from how the pair is clamped, so follow the SKF stand-off-ring and nut-torque procedure rather than assuming the bearings arrive preloaded.
Frequently asked questions
What are the dimensions and catalogue data of SKF 7221?
The SKF 7221 BECBP is a single-row angular-contact ball bearing with 105 mm bore, 190 mm outer diameter and 36 mm width (4.134 × 7.48 × 1.417 in) per ISO 15. From SKF catalogue 17000: basic dynamic load rating C 156 kN, C0 150 kN, fatigue load limit Pu 5.2 kN, reference speed 4,000 r/min, limiting speed 4,300 r/min, mass about 3950 g. It is an open 40° contact-angle bearing with a PA66 cage. Preload and lubricant film move the real thermal limit, so treat 4,000 r/min as catalogue conditions, not a guarantee in the housing.
How does the 7221 bore code work?
The last two digits of 7221 are bore code 21, so 21 × 5 = 105 mm bore. The 190 mm OD and 36 mm width come from the ISO 15 diameter-series plan, shared with the 6221 deep-groove envelope.
What do the 72xx and BECBP designations mean?
The leading 7 marks a single-row angular-contact bearing; the second digit 2 is the ISO diameter series (light section). In the SKF suffix, B denotes the 40° contact angle, E the enhanced internal design, P the glass-fibre PA66 cage. CB adds Normal axial clearance with ground faces for universal DB/DF/DT pair mounting. A 25° variant (suffix A, e.g. ACC) runs faster but carries less thrust.
Can a single 7221 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. Preload light/medium choice changes stiffness and heat, so calculate it from the load diagram rather than torquing until the pair feels tight.
How does 7221 compare with a deep-groove 6221?
Both use the 105×190×36 mm ISO 15 envelope, but the angular-contact 7221 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. Envelope interchange is therefore dimensional only; the application must actually present axial load for the 7221 design to perform.
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.