6311-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 6311-NSK model number is decoded

In the 6300-series (diameter series 3 of ISO 15) the last two digits encode the bore: 6311 carries bore code 11 = 55 mm. Outside diameter 120 mm and width 29 mm come from the ISO 15 boundary-dimensions general plan. With no seal suffix the bearing is open: no shields or seals are fitted and lubrication is supplied by the application. For normal-load mounting with a rotating inner ring on a 55 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. 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

• 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.
• The open 6311-NSK has no lubricant retention: grease escapes and contaminants migrate straight into the 55×120×29 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
• 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.
• 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-NSK.
• Never mix components between two 6311-NSK units: rings, cage and balls are factory-matched and are not field-interchangeable, even between identical designations.
• The open 6311 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 55 mm bore 6311 is in NSK'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 NSK channel if the application sees impact loads.
• At 78.5 kN dynamic load rating (C) and 44.5 kN static (C0), 6311 is a heavy-load NSK bearing for industrial gearboxes and large conveyors; NSK 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; NSK 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 NSK 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 78.5/44.5 kN load ratings, mass 1370 g here are NSK Rolling Bearings E1103 Part C catalogue figures for 6311 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. 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.
• When replacing a failed unit, inspect the shaft and housing seats before fitting the new 6311 — a new bearing pressed onto a worn or oval seat reproduces the original failure mode in a fraction of its expected life.