61921-RSR bearing: complete specifications & equivalents
The 61921-RSR is a ISO 15 radial bearing sized 105 x 145 x 20 mm (bore x OD x width) with RSR sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NSK |
| Bore diameter d | 105 mm |
| Outer diameter D | 145 mm |
| Width B | 20 mm |
| Material | GCr15 |
| Seal / shield | RSR |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 46.5 kN |
| Basic static load rating C0 | 42 kN |
| Mass | 856 g |
| Manufacturer designation | NSK 6921VV |
| Standard | ISO 15 |
| Catalog version | NSK Rolling Bearings E1103 Part C |
| Last verified | 2026-09-24 |
Source: catalog reference (NSK Rolling Bearings E1103 Part C) · extracted 2026-09-24
Dimensions in inches & 61900-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 5.709 in |
| Width B | 0.787 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 20 mm |
| Smallest bore in 61900-series | 10 mm |
| Largest outer diameter in 61900-series | 420 mm |
| Width range across 61900-series | 6–56 mm |
| Bore position in 61900-series (smallest first) | 22 of 37 |
| Bore above smallest 61900-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61921 | ISO-INTERCHANGE | verify Commonly quoted cross reference; confirm against the target catalog before ordering. | ISO 15 envelope interchange; NSK suffix 6921VV maps to industry-neutral RSR. Verify seal design, grease and speed rating per brand catalogue. |
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 61921-RSR model number is decoded
In the 61900-series (ISO 15 diameter series 9) the last two digits encode the bore: 61921 carries bore code 21 = 105 mm. Outside diameter 145 mm and width 20 mm come from the ISO 15 boundary-dimensions general plan. Suffix -RSR denotes two low-friction non-contact elastomer seals; they keep coarse debris out with minimal drag 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
- clutch and transmission assemblies
- robotics and automation joints
- lay shafts and idler shafts
- textile machinery
Known failure patterns
- ingress of fine dust or moisture past the non-contact lip in dirty or wet duty (RSR is not liquid-tight)
- lip-lubricant starvation if the bearing runs dry for extended periods
- fretting corrosion on a loose shaft seat
- cage damage from operation beyond the limiting speed
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 619xx thin section (20.0 mm section height at 105 mm bore) trades load capacity for compactness; stiff, accurately aligned seats are essential or edge loading will spall the raceway early.
- RSR low-friction seals on 61921-RSR run faster than contact-seal 61921-2RS but let fine dust and moisture past the non-contact lip; in dirty or wet duty specify 61921-2RS instead.
- The non-contact lip of 61921-RSR does not retain a lifetime grease fill the way a contact seal does; confirm the regreasing interval for the 105 mm bore position before relying on it as sealed-for-life.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 145 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 61921-RSR.
- NSK catalogues this low-friction non-contact seal as 6921VV (suffix VV), the NSK equivalent of the industry-neutral -RSR spelling on this page. VV is not liquid-tight; NSK's contact-seal suffix DDU (industry-neutral -2RS) is the choice for wet or fine-dust duty.
- The 46.5/42 kN ratings, mass 856 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6921VV; this seal/size combination has no counterpart in the SKF 17000 extract used elsewhere on this site, so the page rests on a single manufacturer source — internal geometry and ratings legitimately differ between brands, so re-verify before substituting in a rated drive.
Frequently asked questions
What are the dimensions of a 61921-RSR bearing?
A 61921-RSR deep-groove ball bearing has a 105 mm bore, 145 mm outer diameter and 20 mm width (4.134 × 5.709 × 0.787 in), per ISO 15 boundary dimensions. It is fitted with two low-friction non-contact rubber seals.
How does the 61921 bore code work?
The last two digits of 61921 are bore code 21, giving 21 × 5 = 105 mm bore. The 145 mm outside diameter and 20 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the RSR suffix on 61921-RSR mean?
RSR means two low-friction non-contact rubber seals. They keep coarse debris out with minimal drag (speed close to the open bearing) but are not liquid-tight; use -2RS contact seals for wet or fine-dust environments.
How does the 61900 compare with other series at the same 105 mm bore?
619 is a thin section one step above 618: 145×20 mm with a 20.0 mm radial section at 105 mm bore; a 6221 on the same bore is substantially larger and more heavily rated.
What is the NSK designation and catalogue data for 61921-RSR?
In the NSK Rolling Bearings catalogue (E1103 Part C) this size is listed as 6921VV — two low-friction non-contact rubber seals (NSK suffix VV), 105×145×20 mm per ISO 15. Quoted values: C 46.5 kN, C0 42 kN, mass 856 g. The industry-neutral page spelling 61921-RSR follows the seal-suffix convention used across this site, not NSK order-number spelling. Reference and limiting speeds are not tabulated in the E1103 dimension tables used here; consult NSK speed tables before high-speed service.
Reviewed & verified by the MPN Base engineering desk against source catalog NSK Rolling Bearings E1103 Part C on 2026-09-24. Read our editorial & correction policy.