61918-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 61918-NSK model number is decoded

61918 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the thin 619xx section (diameter series 9 of ISO 15), multiplying bore code 18 by five gives the 90 mm bore; the 125 mm outside diameter and 18 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 90 mm shaft under normal load, catalogue practice seats it on a k5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. In the NSK catalogue this open execution carries the bare designation; protected variants are ordered separately with suffixes ZZ (steel shields), VV (non-contact rubber seals) and DDU (contact rubber seals).

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Large bores like the 90 mm of 61918-NSK demand clean, burr-free seats; one raised burr under a ring this size cocks the bearing and concentrates load at the raceway edge, cutting life drastically.
• The 619xx thin section at 90 mm bore (17.5 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.
• Storage matters for open bearings: 61918-NSK leaves the factory with rust preventive only, so clean it and apply the service grease at assembly even if the rings look oily from the wrapper.
• Open bearings tolerate the highest speeds in the 61900-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 61918 units.
• Grease compatibility is not guaranteed between fills: mixing lithium and polyurea thickeners in a 61900-series position can soften the mixture and leak — clean out the old fill before switching grease types.
• Measure the shaft, do not trust the drawing: a 90 mm nominal journal worn by even 0.02 mm turns an interference seat into a creeping fit that frets the bore of 61918-NSK.
• The open 61918 has no integral sealing; in the NSK E1103 catalogue the protected variants carry suffixes ZZ (non-contact steel shields), VV (non-contact rubber seals) and DDU (contact rubber seals). NSK does not offer a low-torque contact seal equivalent to NTN's LLH in this catalogue — for high-speed sealed duty specify the VV non-contact seal and an external housing labyrinth.
• At 90 mm bore 61918 is in NSK's medium industrial range; the pressed-steel cage is standard, but large-section 63xx 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 NSK channel if the application sees impact loads.
• NSK rates 61918 at 36 kN dynamic (C) and 31.5 kN static (C0); 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 585 g, 61918 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 90×125×18 mm envelope of 61918 gives a D/d ratio of 1.39 and only 17.5 mm radial section height — this is an ultra-thin section in NSK's E1103 catalogue 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 36/31.5 kN load ratings, mass 585 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6918 on the 90×125×18 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61918 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.
• When replacing a failed unit, inspect the shaft and housing seats before fitting the new 61918 — a new bearing pressed onto a worn or oval seat reproduces the original failure mode in a fraction of its expected life.
• 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.