61921-RSR-NTN bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)) · extracted 2026-09-25

Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.

Cross references & equivalents

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-NTN model number is decoded

61921-RSR uses two non-contact elastomer lips with very low drag; coarse debris stays out, but the bearing is not liquid-tight. Within the thin 619xx section (diameter series 9 of ISO 15), multiplying bore code 21 by five gives the 105 mm bore; the 145 mm outside diameter and 20 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. NTN's non-contact seal suffix is LLB/LLF (catalogue number 6921LLB), mapped here from the industry-neutral -RSR spelling; speed capability matches the open bearing but it is not liquid-tight.

Typical equipment & failure modes

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 at 105 mm bore (20.0 mm section height) cannot shrug off the misalignment a standard section tolerates; keep the housing bores round and aligned, or edge contact will spall the raceways early.
• RSR low-friction seals on 61921-RSR-NTN 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 low-drag lip of 61921-RSR-NTN barely touches the inner ring; after long shelf storage the grease can separate, so rotate the rings by hand and confirm smooth, silent running before fitting.
• The housing bore for the 145 mm OD should be round within IT7; an oval bore pinches the outer ring of 61921-RSR-NTN and shows up later as two-point loaded raceway wear.
• Shaft and housing fillets must clear the bearing chamfer so the 20 mm-wide ring seats square; provide an undercut or withdrawal groove instead of relying on an oversized radius.
• NTN catalogues this low-friction non-contact seal as 6921LLB (suffix LB), mapped here from the industry-neutral -RSR spelling. NTN rates its speed capability the same as the open bearing, but it is not liquid-tight — for wet or fine-dust duty step up to the LLU contact seal (industry-neutral -2RS).
• At 105 mm bore 61921 is in NTN's medium industrial range; the pressed-steel cage is standard but large-section 63xx/64xx sizes at this bore can be ordered with a machined brass cage (suffix M) for heavy-shock or very-low-speed duty — confirm cage material with the NTN channel if the application sees impact loads.
• NTN lists the grease limiting speed at 4300 r/min for 61921; this is a large or heavy-section size where centrifugal force and cage inertia cap the speed — for higher shaft speeds either step to a smaller bearing on the same bore or consult NTN for an oil-lubricated, machined-cage variant.
• NTN rates 61921 at 47 kN dynamic (C) and 42 kN static (C0), 2.52 kN fatigue load limit Cu; this upper-medium rating covers conveyor and gearbox drives, but at these loads the pressed-steel cage can be the limiting factor under shock — consider the machined brass cage (suffix M) for impact duty.
• At 816 g, 61921 requires a soft-jaw vise or arbor press for mounting — never hammer it onto the shaft, and support the opposite ring to avoid brinelling the raceways.
• The 105×145×20 mm envelope of 61921 gives a D/d ratio of 1.38 and only 20.0 mm radial section height — this is an ultra-thin section where shaft deflection and housing ovality directly load the ball-raceway contact; verify shaft stiffness (target deflection under 0.05 mm) before specifying it over a 62-series.
• The 47/42 kN load ratings, 2.52 kN fatigue load limit Cu NTN lists the grease limiting speed at 4300 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 816 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6921LLB on the 105×145×20 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61921 in a rated drive.
• Two NTN bearings of the same designation from different production lots can carry minor internal-geometry revisions; for paired or preloaded arrangements on one shaft, order a single lot through the NTN distributor.
• Order the C3 internal-clearance version (61921 with C3 after the seal code) when the shaft fit is tight or the shaft-to-housing temperature gradient exceeds roughly 10 °C — the residual clearance after mounting, not the catalogue CN figure, decides service life.