61904-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 61904-FAG model number is decoded

61904 is supplied open, without shields or seals, so the arrangement around it must supply and retain the lubricant. Within the thin 619xx section (diameter series 9 of ISO 15), multiplying bore code 04 by five gives the 20 mm bore; the 37 mm outside diameter and 9 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 20 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

• At a 20 mm bore, a shaft-seat burr or an overtight setscrew can score the thin inner ring of 61904-FAG; check shaft finish and runout (target Ra ≤ 1.6 µm) before pressing it home.
• The 619xx thin section at 20 mm bore (8.5 mm section height) cannot shrug off the misalignment a standard section tolerates; keep the housing bores round and aligned, or edge contact will spall the raceways early.
• The open 61904-FAG has no lubricant retention: grease escapes and contaminants migrate straight into the 20×37×9 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
• Open bearings tolerate the highest speeds in the 61900-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 61904 units.
• Grease compatibility is not guaranteed between fills: mixing lithium and polyurea thickeners in a 61900-series position can soften the mixture and leak — clean out the old fill before switching grease types.
• Shaft and housing fillets must clear the bearing chamfer so the 9 mm-wide ring seats square; provide an undercut or withdrawal groove instead of relying on an oversized radius.
• The open 61904 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.
• The 28500 r/min mechanical limiting speed puts 61904 at the top of the HR 1 deep-groove speed range (thermal reference speed 17000 r/min); at these speeds cage design and grease shear dominate — run open with oil-mist or air-over-oil lubrication and verify the thermal reference speed for the actual load before committing.
• The 20 mm bore puts 61904 in Schaeffler's light industrial range; the standard cage and CN clearance cover most fractional-horsepower motor and small-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 61904 at 6.38 kN dynamic (C) and 3.68 kN static (C0); this light-to-medium rating suits fractional-horsepower drives and instruments — verify the equivalent dynamic load stays well below C for conveying or gearbox duty with shock.
• At only 40 g, 61904 is a lightweight FAG bearing that can be handled by hand; still press it onto the shaft with a sleeve against the inner ring — never through the balls or outer ring.
• The 20×37×9 mm envelope of 61904 gives a D/d ratio of 1.85 and 8.5 mm radial section height — a standard FAG medium section balancing load capacity and speed; the standard cage is adequate up to the listed speeds and C3 clearance is the common hot-shaft choice.
• The 6.38/3.68 kN load ratings, mass 40 g here are Schaeffler HR 1 Rolling Bearings (Jan 2020) catalogue figures for 61904-FAG on the 20×37×9 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61904 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.
• For hot shafts above roughly 100 °C continuous, consult Schaeffler about seal material and grease options for the 2RSR execution of 61904; the standard NBR lip is the economical general-duty choice, not the high-temperature one.