61808-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 61808-RSR-NTN model number is decoded

In the 61800-series (diameter series 8 of ISO 15) the last two digits encode the bore: 61808 carries bore code 08 = 40 mm. Outside diameter 52 mm and width 7 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 40 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. NTN's non-contact seal suffix is LLB/LLF (catalogue number 6808JRLLB), 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

• A 40 mm shaft for 61808 should be finished to Ra ≤ 1.6 µm with square seating faces; at this bore a scored or oval journal shows up directly as running noise and early raceway damage.
• Only 6.0 mm of radial section separates bore and OD on the 618xx series at 40 mm: ring flex from clamping or an oval housing bore transfers straight into raceway stress, so seat roundness matters more here than on a 6208.
• RSR low-friction seals on 61808-RSR-NTN run faster than contact-seal 61808-2RS but let fine dust and moisture past the non-contact lip; in dirty or wet duty specify 61808-2RS instead.
• The non-contact lip of 61808-RSR-NTN does not retain a lifetime grease fill the way a contact seal does; confirm the regreasing interval for the 40 mm bore position before relying on it as sealed-for-life.
• Deep-groove ball bearings tolerate only minutes of misalignment; if the 52 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 61808-RSR-NTN.
• Shaft and housing fillets must clear the bearing chamfer so the 7 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 6808JRLLB (suffix RLLB), 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).
• The 40 mm bore puts 61808 in NTN's general-purpose industrial range; the standard pressed-steel cage and CN clearance cover most electric-motor and pump duty, but for continuous high-speed use specify the LLH low-torque seal (not LLU) and confirm the housing allows the listed limiting speed.
• At 8000 r/min the grease limiting speed for 61808 covers most general-purpose industrial drives; the open or shielded execution can run continuously at this speed with standard lithium-soap grease.
• NTN rates 61808 at 5.65 kN dynamic (C) and 4.4 kN static (C0), 0.29 kN fatigue load limit Cu; this light-to-medium rating suits fractional-horsepower drives and instruments — for conveying or gearbox duty with shock loads, verify the equivalent dynamic load stays well below C.
• At only 33 g, 61808 is a lightweight bearing that can be handled by hand; still, press it onto the shaft with a sleeve against the inner ring — never through the balls or outer ring.
• The 40×52×7 mm envelope of 61808 gives a D/d ratio of 1.30 and only 6.0 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 5.65/4.4 kN load ratings, 0.29 kN fatigue load limit Cu NTN lists the grease limiting speed at 8000 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 33 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6808JRLLB on the 40×52×7 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61808 in a rated drive.
• Standard catalogue stock of 61808 is the general-purpose execution; for low-noise motor duty NTN offers low-torque seal and special-grease variants in this size class, which are separate order numbers.
• Order the C3 internal-clearance version (61808 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.