6408-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 6408-FAG model number is decoded

6408 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the heavy 64xx section (diameter series 4 of ISO 15), multiplying bore code 08 by five gives the 40 mm bore; the 110 mm outside diameter and 27 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 40 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

• Sizes around 40 mm bore are normally pressed on cold with a sleeve against the inner-ring face; the press force must never route through the outer ring or the balls of 6408-FAG.
• The 64xx heavy section at 40 mm bore exists for high radial load at moderate rpm; its 110 mm OD and 27 mm width demand a larger housing, and grease life at motor speeds is short — treat it as a low-speed, high-load choice.
• Storage matters for open bearings: 6408-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 6400-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 6408 units.
• Deep-groove ball bearings tolerate only minutes of misalignment; if the 110 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 6408-FAG.
• A 40 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 open 6408 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 9500 r/min mechanical limiting speed (thermal reference speed 7700 r/min), 6408 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.
• The 40 mm bore puts 6408 in Schaeffler's general-purpose industrial range; the standard cage and CN clearance cover most electric-motor and pump duty, and FAG's X-life generation of these sizes carries higher ratings than legacy HR 1 printings — check the current eKatalog listing before reordering.
• FAG rates 6408 at 68 kN dynamic (C) and 38 kN static (C0); this upper-medium rating covers conveyor and gearbox drives, but under shock the pressed steel cage can become the limiting element — consider the machined brass cage (suffix M) for impact duty.
• At 1220 g (1.2 kg), 6408 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 40×110×27 mm envelope of 6408 gives a D/d ratio of 2.75 and 35.0 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 68/38 kN load ratings, mass 1220 g here are Schaeffler HR 1 Rolling Bearings (Jan 2020) catalogue figures for 6408-C on the 40×110×27 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6408 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 standard tolerance for this size is P0 (PN); P6/P5 precision executions exist for spindle-adjacent duty but carry different order numbers in the Schaeffler system — they are not a selectable sorting of standard stock.
• Mixing old and new FAG generations of the same designation in one arrangement is dimensionally acceptable, but where ratings matter — preloaded or matched sets — order both positions from the same generation and lot.