6308-ZZ-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 6308-ZZ-FAG model number is decoded

6308-ZZ carries two non-contact sheet-steel shields that hold the factory grease in and keep coarse debris out; they do not seal against liquids. Within the medium 63xx section (diameter series 3 of ISO 15), multiplying bore code 08 by five gives the 40 mm bore; the 90 mm outside diameter and 23 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. Schaeffler HR 1 catalogue order number: 6308-C-2Z (FAG suffix 2Z), two non-contact steel shields, mapped here from the industry-neutral -ZZ spelling.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• A 40 mm shaft for 6308 should be finished to Ra ≤ 1.6 µm with square seating faces; at this bore a scored or oval journal shows up directly as running noise and early raceway damage.
• The 63xx medium series gains rating at 40 mm bore through a 90 mm OD and 23 mm width; the heavier rolling elements also trade away some speed versus a 6208.
• Do not wash 6308-ZZ-FAG in solvent before mounting: the grease inside the shielded cavity is the service fill, and solvent creeping past the shield gap strips it out.
• Shielded 6308-ZZ-FAG units are typically greased for life; prying the shields out for regreasing usually bends them and leaves a gap that throws grease in service.
• Suffixes stack in a defined order — clearance follows the seal code, e.g. 6308-ZZ-FAG-C3. No clearance suffix means normal CN clearance.
• 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.
• Schaeffler HR 1 lists the shielded version as 6308-C-2Z — FAG suffix 2Z, two non-contact steel shields. The industry-neutral page spelling is -ZZ; quote the FAG order number when buying through a Schaeffler channel.
• At 10100 r/min mechanical limiting speed (thermal reference speed 9900 r/min), 6308 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 6308 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 6308 at 47 kN dynamic (C) and 25 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 665 g, 6308 requires a soft-jaw vise or arbor press for mounting — never hammer it onto the shaft, and support the opposite ring to avoid brinelling the raceways.
• The 40×90×23 mm envelope of 6308 gives a D/d ratio of 2.25 and 25.0 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 47/25 kN load ratings, mass 665 g here are Schaeffler HR 1 Rolling Bearings (Jan 2020) catalogue figures for 6308-C-2Z on the 40×90×23 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 6308 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.
• 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.