61908-RSR-NSK bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NSK Rolling Bearings E1103 Part C) · extracted 2026-09-24

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 61908-RSR-NSK model number is decoded

In the 61900-series (diameter series 9 of ISO 15) the last two digits encode the bore: 61908 carries bore code 08 = 40 mm. Outside diameter 62 mm and width 12 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. NSK's non-contact seal suffix is VV (catalogue number 6908VV), mapped here from the industry-neutral -RSR spelling; speed capability is close to the open bearing but VV is not liquid-tight.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Sizes around 40 mm bore are normally pressed on cold with a sleeve against the inner-ring face; the press force must never route through the outer ring or the balls of 61908-RSR-NSK.
• The 619xx thin section (11.0 mm section height at 40 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 61908-RSR-NSK run faster than contact-seal 61908-2RS but let fine dust and moisture past the non-contact lip; in dirty or wet duty specify 61908-2RS instead.
• The non-contact lip of 61908-RSR-NSK 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.
• Do not quieten a noisy bearing by preloading it: the 61900-series is a deep-groove design, not angular-contact; axial preload raises temperature and shortens grease life.
• Measure the shaft, do not trust the drawing: a 40 mm nominal journal worn by even 0.02 mm turns an interference seat into a creeping fit that frets the bore of 61908-RSR-NSK.
• NSK catalogues this low-friction non-contact seal as 6908VV (suffix VV), mapped here from the industry-neutral -RSR spelling. NSK rates its speed capability close to the open bearing, but VV is not liquid-tight — for wet or fine-dust duty step up to the DDU contact seal (industry-neutral -2RS).
• The 40 mm bore puts 61908 in NSK's general-purpose industrial range; the standard pressed-steel cage and CN clearance cover most electric-motor and pump duty. NSK's VV non-contact seal is the high-speed choice here — DDU contact seal costs roughly 30–40% of the open-bearing speed ceiling.
• At 15 kN dynamic load rating (C) and 10 kN static (C0), 61908 is a medium-load NSK bearing suitable for most electric-motor and pump duty; the C0/C0r ratio matters for preloaded or thrust-loaded arrangements, so confirm the static safety factor with the NSK catalogue.
• At 112 g, 61908 is light enough for hand assembly but should be pressed on with a fitting sleeve against the inner ring; do not strike the outer ring or cage with a hammer.
• The 40×62×12 mm envelope of 61908 gives a D/d ratio of 1.55 and 11.0 mm radial section height — this NSK thin section saves space but is sensitive to misalignment and shock; confirm the housing stays round within IT7 and the shaft does not deflect past the raceway contact angle under load.
• The 15/10 kN load ratings, mass 112 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6908VV on the 40×62×12 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61908 in a rated drive. NSK does not tabulate reference or limiting speeds in the E1103 Part C dimension tables used for this page — consult NSK's separate speed-rating tables before high-speed service.
• NSK does not recommend washing new shielded or sealed bearings; the rust-preventive film on open units is compatible with standard lithium greases and needs no removal unless the application demands a special fill.
• NSK's VV non-contact seal keeps frictional torque close to the open 61908; in motor duty where heat build-up matters, VV is the usual compromise between debris protection and speed capability.