61988 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 61988 model number is decoded

61988 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 88 by five gives the 440 mm bore; the 600 mm outside diameter and 74 mm width follow the same boundary-dimension plan. For a rotating inner ring on a 440 mm shaft under normal load, catalogue practice seats it on a m6 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 440 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 (80.0 mm section height at 440 mm bore) trades load capacity for compactness; stiff, accurately aligned seats are essential or edge loading will spall the raceway early.
• The open 61988 has no lubricant retention: grease escapes and contaminants migrate straight into the 440×600×74 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
• Storage matters for open bearings: 61988 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.
• Shaft and housing fillets must clear the bearing chamfer so the 74 mm-wide ring seats square; provide an undercut or withdrawal groove instead of relying on an oversized radius.
• 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.
• The open 61988 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.
• The 440 mm bore places 61988 in NTN's upper maximum-size range; at this diameter the bearing mass is substantial and mounting requires induction heating of the inner ring (max 120 °C) with a mechanical puller. NTN supplies a machined brass cage (suffix M) and expects oil lubrication with a defined relubrication interval.
• NTN lists the grease limiting speed at only 890 r/min for 61988; this is a very large or heavy-section size where centrifugal force and cage inertia cap the speed — for higher shaft speeds either step to a smaller bearing on the same bore or consult NTN for an oil-lubricated, machined-cage variant.
• At 405 kN dynamic load rating (C) and 615 kN static (C0), 18 kN fatigue load limit Cu, 61988 is a very-heavy-load bearing for large industrial gearboxes and steel-mill equipment; NTN supplies a machined brass cage (suffix M) and expects an application review, because catalogue L10 life alone does not capture the shock and misalignment loads at this rating.
• At 60000 g (60.0 kg), 61988 is an extremely heavy bearing at the top of the single-row deep-groove range; NTN mandates induction heating (max 120 °C), a dedicated lifting fixture, and a machined brass cage (suffix M). Consult NTN engineering for the mounting and handling procedure before installation.
• The 440×600×74 mm envelope of 61988 gives a D/d ratio of 1.36 and only 80.0 mm radial section height — this is an ultra-thin section where shaft deflection and housing ovality directly load the ball-raceway contact; verify shaft stiffness (target deflection under 0.05 mm) before specifying it over a 62-series.
• The 405/615 kN load ratings, 18 kN fatigue load limit Cu NTN lists the grease limiting speed at 890 r/min for this designation; oil-mist or jet lubrication raises the ceiling but requires a sealed-housing review. and 60000 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6988 on the 440×600×74 mm ISO 15 envelope; internal geometry and ratings legitimately differ between brands, so re-verify before substituting another manufacturer's 61988 in a rated drive.
• Standard catalogue stock of 61988 is the general-purpose execution; for low-noise motor duty NTN offers low-torque seal and special-grease variants in this size class, which are separate order numbers.
• NTN date-codes its packaging; rotate stock first-in-first-out, because the grease inside sealed units ages on the shelf — after three to five years of storage, check the grease condition before putting the bearing into service.