6318-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 6318-RSR-NTN model number is decoded

In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6318 carries bore code 18 = 90 mm. Outside diameter 190 mm and width 43 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 90 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 6318LLB), 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 90 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 63xx medium series gains rating at 90 mm bore through a 190 mm OD and 43 mm width; the heavier rolling elements also trade away some speed versus a 6218.
• RSR low-friction seals on 6318-RSR-NTN run faster than contact-seal 6318-2RS but let fine dust and moisture past the non-contact lip; in dirty or wet duty specify 6318-2RS instead.
• The low-drag lip of 6318-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.
• Suffixes stack in a defined order — clearance follows the seal code, e.g. 6318-RSR-NTN-C3. No clearance suffix means normal CN clearance.
• Assign fits by which ring rotates: an interference shaft fit for a rotating inner ring; if the outer ring rotates instead, reverse the logic — a loose rotating ring creeps and frets its seat.
• NTN catalogues this low-friction non-contact seal as 6318LLB (suffix LLB), 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 90 mm bore 6318 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 3600 r/min for 6318; 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.
• At 158 kN dynamic load rating (C) and 107 kN static (C0), 7.1 kN fatigue load limit Cu, 6318 is a heavy-load bearing for industrial gearboxes and large conveyors; NTN expects a machined brass cage (suffix M) at this rating for shock duty, and the static C0 must be checked against any mounting or lifting loads.
• At 4910 g (4.9 kg), 6318 needs mechanical handling for mounting; NTN recommends induction heating the inner ring (max 120 °C) rather than pressing cold, and a lifting eye if the housing is pre-assembled.
• The 90×190×43 mm envelope of 6318 gives a D/d ratio of 2.11 and 50.0 mm radial section height — a heavy section built for high-load, lower-speed duty; specifying it in a high-rpm motor generates excess heat and shortens grease life, so prefer a 62/63-series there.
• The 158/107 kN load ratings, 7.1 kN fatigue load limit Cu NTN lists the grease limiting speed at 3600 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 4910 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6318LLB on the 90×190×43 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6318 in a rated drive.
• NTN date-codes its packaging; rotate stock first-in-first-out, because the grease inside sealed units ages on the shelf — after three to five years of storage, check the grease condition before putting the bearing into service.
• Order the C3 internal-clearance version (6318 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.