6221-ZZ bearing: complete specifications & equivalents
The 6221-ZZ is a ISO 15 radial bearing sized 105 x 190 x 36 mm (bore x OD x width) with ZZ sealing. 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 | ZZ |
| Internal clearance | CN / C3 available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 140 kN |
| Basic static load rating C0 | 104 kN |
| Fatigue load limit Pu | 3.65 kN |
| Reference speed (thermal) | 7000 rpm |
| Limiting speed (mechanical) | 3600 rpm |
| Operating temperature | -30 to +120 °C |
| Mass | 3900 g |
| Manufacturer designation | SKF 6221-2Z |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-25 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-24
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); 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 & 6200-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 6200-series | 3 mm |
| Largest outer diameter in 6200-series | 540 mm |
| Width range across 6200-series | 2.5–85 mm |
| Bore position in 6200-series (smallest first) | 30 of 45 |
| Bore above smallest 6200-series size | 102 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 6221-2RS | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 6221-NSK | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 6221-RSR | NSK | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; seal variant differs (ZZ vs RSR) — confirm sealing suits the duty. |
| 6221-ZZ-NSK | NSK | 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. |
| 6221-2RS-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 6221-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 6221-RSR-NTN | NTN | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; seal variant differs (ZZ vs RSR) — confirm sealing suits the duty. |
| 6221-ZZ-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. |
| 7221 | SKF | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | — |
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 6221-ZZ model number is decoded
6221-ZZ carries two non-contact sheet-steel shields that hold the factory grease in and keep coarse debris out; they do not seal against liquids. Within the light 62xx section (diameter series 2 of ISO 15), multiplying bore code 21 by five gives the 105 mm bore; the 190 mm outside diameter and 36 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 105 mm shaft under normal load, catalogue practice seats it on a m6 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. SKF's own suffix is 2Z (this page's industry-neutral spelling is -ZZ); catalogue number 6221-2Z.
Typical equipment & failure modes
Common applications
- large gearboxes
- industrial fans and blowers
- hoists and winches
- heavy conveyors
Known failure patterns
- fine-particle abrasion when non-contact shields let dust past in dirty duty
- grease aging in the shield-for-life cavity with no relubrication path
- brinelling from static overload or hammering during mounting
- false brinelling from vibration while the shaft is stationary
Selection pitfalls — read before you substitute
- Large bores like the 105 mm of 6221-ZZ demand clean, burr-free seats; one raised burr under a ring this size cocks the bearing and concentrates load at the raceway edge, cutting life drastically.
- At 105 mm bore the 62xx light series is the workhorse section; its 190×36 mm envelope is what most motor and gearbox seats are machined for, so any alternative section must be checked against both this OD and this width, not the bore alone.
- Do not wash 6221-ZZ in solvent before mounting: the grease inside the shielded cavity is the service fill, and solvent creeping past the shield gap strips it out.
- Shielded 6221-ZZ units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
- Suffixes stack in a defined order — clearance follows the seal code, e.g. 6221-C3. No clearance suffix means normal CN clearance.
- Measure the shaft, do not trust the drawing: a 105 mm nominal journal worn by even 0.02 mm turns an interference seat into a creeping fit that frets the bore of 6221-ZZ.
- SKF spells the shielded version 6221-2Z (one shield: 6221-Z), not "-ZZ": the suffix language differs by brand even though the ISO envelope is identical, so quote the brand designation when ordering.
- The single-shield execution 6221-Z is a distinct order number in catalogue 17000: it suits open gears or oil-bath arrangements where the unshielded face faces the lubricant, and it is not interchangeable with the double-shield 6221-2Z for high-contamination positions.
- The 140/104 kN ratings here are SKF Explorer-class figures from catalogue PUB BU/P1 17000/1 EN (Oct 2018); SKF can revise internal geometry and ratings without changing the designation, so treat the catalogue version and date as part of the specification and re-verify for critical drives.
Frequently asked questions
What are the dimensions of a 6221-ZZ bearing?
A 6221-ZZ deep-groove ball bearing has a 105 mm bore, 190 mm outer diameter and 36 mm width (4.134 × 7.48 × 1.417 in), per ISO 15 boundary dimensions. It is fitted with two non-contact metallic shields.
What internal clearance does 6221-ZZ have?
Unless a clearance suffix says otherwise, 6221-ZZ is manufactured to normal (CN) radial internal clearance. Tight fits and hot shafts consume clearance in service — for those conditions order the C3 execution of 6221 and verify the residual clearance after mounting.
How should 6221-ZZ be mounted?
Apply the mounting force to the ring being fitted: on a 105 mm shaft seat the press load must pass through the inner-ring face only. Induction heating of the inner ring (max 120 °C) is the clean method at this size. Never strike the outer ring, the cage or the seals.
What lubrication does 6221-ZZ need?
6221-ZZ is greased at the factory and the shields hold the fill for the bearing's service life; relubrication is not intended, and adding grease through the shield gap usually forces dirt in with it.
What is the SKF designation and catalogue data for 6221-ZZ?
In the SKF Rolling Bearings catalogue this size is listed as 6221-2Z — two non-contact sheet-metal shields, 105×190×36 mm per ISO 15. Quoted values: C 140 kN, C0 104 kN, Pu 3.65 kN, limiting speed 3600 r/min, mass 3900 g. Brand suffixes (2Z, 2RSH, 2RSL) differ from the industry-neutral spelling 6221-ZZ.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-25. Read our editorial & correction policy.