6311-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 6311-RSR-NTN model number is decoded

6311-RSR uses two non-contact elastomer lips with very low drag; coarse debris stays out, but the bearing is not liquid-tight. Within the medium 63xx section (diameter series 3 of ISO 15), multiplying bore code 11 by five gives the 55 mm bore; the 120 mm outside diameter and 29 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 55 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. NTN's non-contact seal suffix is LLB/LLF (catalogue number 6311LLB), 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

• Temperature rise and interference fits consume internal clearance on this 55 mm bore: a CN bearing on a tight, hot shaft can lose all residual clearance — size 6311 with C3 for those conditions.
• The 63xx medium series gains rating at 55 mm bore through a 120 mm OD and 29 mm width; the heavier rolling elements also trade away some speed versus a 6211.
• The low-drag lip of 6311-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 non-contact lip of 6311-RSR-NTN does not retain a lifetime grease fill the way a contact seal does; confirm the regreasing interval for the 55 mm bore position before relying on it as sealed-for-life.
• A 55 mm bore listing showing the right d/D/B but no standard or precision-class reference may be a loose-tolerance import; measure bore/OD spread before fitting it to a machined shaft.
• The housing bore for the 120 mm OD should be round within IT7; an oval bore pinches the outer ring of 6311-RSR-NTN and shows up later as two-point loaded raceway wear.
• NTN catalogues this low-friction non-contact seal as 6311LLB (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 55 mm bore 6311 is in NTN's upper general-purpose range; the pressed-steel cage is standard but mid-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 NTN channel if the application sees impact loads.
• At 5800 r/min the grease limiting speed for 6311 covers medium-duty industrial drives; the open or shielded execution can run continuously at this speed with standard lithium-soap grease.
• At 79.5 kN dynamic load rating (C) and 45 kN static (C0), 3.5 kN fatigue load limit Cu, 6311 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 1370 g (1.4 kg), 6311 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 55×120×29 mm envelope of 6311 gives a D/d ratio of 2.18 and 32.5 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 79.5/45 kN load ratings, 3.5 kN fatigue load limit Cu NTN lists the grease limiting speed at 5800 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 1370 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6311LLB on the 55×120×29 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6311 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.
• Standard catalogue stock of 6311 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.