61903-NTN bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)) · extracted 2026-09-25

Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203-3/E (2024)); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.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 61903-NTN model number is decoded

61903 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 17 by five gives the 17 mm bore; the 30 mm outside diameter and 7 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 17 mm shaft under normal load, catalogue practice seats it on a j5 shaft fit with an H7 housing bore — confirm against the actual load direction and magnitude before committing. In the NTN catalogue this open execution carries the bare designation; protected variants are ordered separately with suffixes ZZ (shields), LLB/LLF (non-contact seals), LLH (low-torque contact seal) and LLU (contact seal).

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Mount this 17 mm bore bearing by heating the inner ring (induction heater, max 120 °C) — never drive it home through the outer ring or balls, that brinells the raceways.
• The 619xx thin section at 17 mm bore (6.5 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.
• Storage matters for open bearings: 61903-NTN 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 61900-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 61903 units.
• The housing bore for the 30 mm OD should be round within IT7; an oval bore pinches the outer ring of 61903-NTN and shows up later as two-point loaded raceway wear.
• Assign fits by which ring rotates: an interference shaft fit for a rotating inner ring; if the outer ring rotates instead, reverse the logic — a loose rotating ring creeps and frets its seat.
• The open 61903 has no integral sealing; in the NTN 2203 catalogue the protected variants carry suffixes ZZ (non-contact steel shields), LLB/LLF (non-contact rubber seals), LLU (contact rubber seals) and LLH (a low-torque contact seal with higher speed capability than LLU). A JR or JRX suffix (printed for some thin-section sizes) denotes a pressed-steel cage, not a seal.
• At 17 mm bore the 61903 sits in NTN's small-bore range; ABEC-1/P0 runout is standard, and the pressed-steel cage is adequate up to the grease limiting speed — for higher accuracy (spindles, instruments) ask NTN for a P6 or P5 tolerance-class listing before relying on catalogue P0 figures.
• NTN rates 61903 at 22000 r/min grease limiting speed — this is a high-speed electric-motor range; keep the grease fill at 20–30% of the free bearing volume and avoid mixing grease thickener types if regreasing through the housing.
• NTN rates 61903 at 5.15 kN dynamic (C) and 2.58 kN static (C0), 0.2 kN fatigue load limit Cu; this light-to-medium rating suits fractional-horsepower drives and instruments — for conveying or gearbox duty with shock loads, verify the equivalent dynamic load stays well below C.
• At only 18 g, 61903 is a lightweight 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 17×30×7 mm envelope of 61903 gives a D/d ratio of 1.76 and 6.5 mm radial section height — a standard medium section that balances load capacity and speed; for this geometry the pressed-steel cage is adequate up to the listed limiting speed, and C3 clearance is the common choice for hot shafts.
• The 5.15/2.58 kN load ratings, 0.2 kN fatigue load limit Cu NTN lists the grease limiting speed at 22000 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 18 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6903JRX on the 17×30×7 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61903 in a rated drive.
• Order the C3 internal-clearance version (61903 with C3 after the seal code) when the shaft fit is tight or the shaft-to-housing temperature gradient exceeds roughly 10 °C — the residual clearance after mounting, not the catalogue CN figure, decides service life.
• NTN's pressed-steel cage (no cage suffix) is the quiet standard for this size; for sustained running close to the limiting speed or for heavy shock duty, ask the NTN channel whether a machined-cage execution of 61903 is listed.