6311-FAG bearing: complete specifications & equivalents

Specification table

Source: catalog reference (HR 1 Rolling Bearings (Jan 2020)) · extracted 2026-09-25

Parameters extracted from the official FAG Rolling Bearings catalogue (HR 1 Rolling Bearings (Jan 2020)); FAG® is a trademark of Schaeffler Technologies AG & Co. KG, used here for identification only — mpnbase is not an authorized FAG/Schaeffler distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at schaeffler.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-FAG model number is decoded

6311 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. 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. In the Schaeffler HR 1 catalogue this open execution carries the bare designation; protected variants are ordered separately with suffixes 2Z (steel shields), 2RZ (non-contact rubber seals) and 2RSR (lip-contact rubber seals).

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Interference on a 55 mm shaft plus running heat consumes radial clearance: where the shaft runs hot or the fit is tight, order 6311 with C3 clearance and re-check the residual value after mounting.
• The 63xx medium section at 55 mm bore gains dynamic rating through larger rolling elements on a 120 mm OD; the penalty is mass and a lower limiting speed than the 6211 — do not specify it for speed-critical shafts.
• Storage matters for open bearings: 6311-FAG 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 6300-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 6311 units.
• Do not quieten a noisy bearing by preloading it: the 6300-series is a deep-groove design, not angular-contact; axial preload raises temperature and shortens grease life.
• Deep-groove ball bearings tolerate only minutes of misalignment; if the 120 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6311-FAG.
• The open 6311 has no integral sealing; in the Schaeffler HR 1 catalogue the protected variants carry suffixes 2Z (two steel shields), 2RZ (two non-contact rubber seals) and 2RSR (two lip-contact rubber seals). Do not confuse FAG's 2RZ with a contact seal — the RZ lip does not touch the inner ring, which is why its speed capability stays close to the open bearing.
• At 8500 r/min mechanical limiting speed (thermal reference speed 7800 r/min), 6311 covers general-purpose motor and pump duty; keep grease fill at 25–35% of free volume and verify the housing can dissipate the frictional heat at the thermal reference speed.
• At 55 mm bore 6311 is in Schaeffler'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 shock or very-low-speed duty — confirm cage material with the Schaeffler channel if the application sees impact loads.
• At 83 kN dynamic load rating (C) and 47.5 kN static (C0), 6311 is a heavy-load FAG bearing for industrial gearboxes and large conveyors; Schaeffler expects a machined brass cage (suffix M) at this rating for shock duty, and C0 must be checked against mounting or lifting loads.
• At 1330 g (1.3 kg), 6311 needs mechanical handling for mounting; Schaeffler recommends induction heating the inner ring (max 120 °C) rather than pressing cold, and a lifting provision 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 FAG section 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 83/47.5 kN load ratings, mass 1330 g here are Schaeffler HR 1 Rolling Bearings (Jan 2020) catalogue figures for 6311-C 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. Where FAG has since released an X-life version of this size, its expanded C/C0 ratings supersede the HR 1 print values quoted here.
• FAG sealed units arrive greased for life with a lithium-soap fill; Schaeffler quotes a shelf life for greased bearings and recommends running stock first-in-first-out rather than re-greasing aged sealed units.
• Schaeffler's medias/eKatalog is the live source for the current execution of 6311: cage material, seal lip design and ratings can be revised between catalogue generations without any designation change.