61821-ZZ bearing: complete specifications & equivalents
The 61821-ZZ is a ISO 15 radial bearing sized 105 x 130 x 13 mm (bore x OD x width) with ZZ sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Bore diameter d | 105 mm |
| Outer diameter D | 130 mm |
| Width B | 13 mm |
| Seal / shield | ZZ |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Mass (geometry estimate) | 306 g |
| Standard | ISO 15 |
| Catalog version | iso15-ed4-geometry |
| Last verified | 2026-09-24 |
Source: ISO 15 boundary-dimensions standard · extracted 2026-09-24
Standard-interchange bearing: dimensions per ISO 15; CN clearance, P0 tolerance and a stamped-steel cage are catalogue defaults unless the supplier states otherwise, and mass is a geometry-derived estimate. Brand catalogue load ratings and limiting speeds for 61821 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & 61800-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 5.118 in |
| Width B | 0.512 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 12.5 mm |
| Smallest bore in 61800-series | 10 mm |
| Largest outer diameter in 61800-series | 420 mm |
| Width range across 61800-series | 5–38 mm |
| Bore position in 61800-series (smallest first) | 22 of 39 |
| Bore above smallest 61800-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61821 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×130×13 mm envelope per ISO 15; seal variant differs (ZZ vs OPEN) — confirm sealing suits the duty. |
| 61821-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×130×13 mm envelope per ISO 15; seal variant differs (ZZ vs 2RS) — confirm sealing suits the duty. |
| 61821-RSR | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×130×13 mm envelope per ISO 15; seal variant differs (ZZ vs RSR) — confirm sealing suits the duty. |
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 61821-ZZ model number is decoded
In the 61800-series (ISO 15 diameter series 8) the last two digits encode the bore: 61821 carries bore code 21 = 105 mm. Outside diameter 130 mm and width 13 mm come from the ISO 15 boundary-dimensions general plan. Suffix -ZZ denotes two non-contact metallic shields; they retain grease and block coarse debris but are not liquid-tight. For normal-load mounting with a rotating inner ring on a 105 mm shaft, typical catalogue practice is a m6 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude.
Typical equipment & failure modes
Common applications
- packaging machinery
- space-constrained gearboxes
- clutch and transmission assemblies
- robotics and automation joints
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
- cage damage from operation beyond the limiting speed
- electrical pitting in VFD-driven motors without grounding protection
Selection pitfalls — read before you substitute
- Mount this 105 mm bore bearing by heating the inner ring (induction heater, max 120 °C) — never drive it home through the outer ring or balls, that brinells the raceways.
- The 618xx thin section at 105 mm bore has only a 12.5 mm radial section height: it saves space but is highly sensitive to misalignment, shaft deflection and shock loads — verify shaft stiffness before choosing it over a 6221.
- ZZ shields are non-contact: 61821-ZZ blocks chips and coarse dust but is not waterproof — do not install it expecting a pressure-wash seal, step up to 61821-2RS for that.
- Shielded 61821-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.
- Do not quieten a noisy bearing by preloading it: the 61800-series is a deep-groove design, not angular-contact; axial preload raises temperature and shortens grease life.
Frequently asked questions
What are the dimensions of a 61821-ZZ bearing?
A 61821-ZZ deep-groove ball bearing has a 105 mm bore, 130 mm outer diameter and 13 mm width (4.134 × 5.118 × 0.512 in), per ISO 15 boundary dimensions. It is fitted with two non-contact metallic shields. Geometry-based estimated mass is about 306 g for a steel-cage unit; catalogue masses vary slightly with seal and cage design.
How does the 61821 bore code work?
The last two digits of 61821 are bore code 21, giving 21 × 5 = 105 mm bore. The 130 mm outside diameter and 13 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the ZZ suffix on 61821-ZZ mean?
ZZ means two non-contact sheet-metal shields, one each side. They retain factory grease and block coarse particles with little friction, but do not seal against liquids, fine dust or pressure washing.
How does the 61800 compare with other series at the same 105 mm bore?
618 is an extra-thin section: 130×13 mm, only 12.5 mm radial section at 105 mm bore, far smaller than a 6221, for space-limited layouts at the cost of load rating and misalignment tolerance.
Are 61821 bearings from different brands interchangeable?
For boundary dimensions, yes: every brand's 61821 uses the same ISO 15 envelope (105×130×13 mm). Load ratings, limiting speeds, clearance, precision class and sealing design can differ, so verify those in the supplier catalogue when substituting. Seal suffixes also differ by brand (2RS, DDU, LLU and similar).
Reviewed & verified by the MPN Base engineering desk against source catalog iso15-ed4-geometry on 2026-09-24. Read our editorial & correction policy.