61988 bearing: complete specifications & equivalents
The 61988 is a ISO 15 radial bearing sized 440 x 600 x 74 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 440 mm |
| Outer diameter D | 600 mm |
| Width B | 74 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 405 kN |
| Basic static load rating C0 | 615 kN |
| Fatigue load limit Pu | 18 kN |
| Limiting speed (mechanical) | 890 rpm |
| Mass | 60000 g |
| Manufacturer designation | NTN 6988 |
| Standard | ISO 15 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203-3/E (2024) |
| Last verified | 2026-09-25 |
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.
Dimensions in inches & 61900-series range
| Bore d | 17.323 in |
|---|---|
| Outer diameter D | 23.622 in |
| Width B | 2.913 in |
| ISO bore code | 88 |
| Radial section height (D−d)/2 | 80 mm |
| Smallest bore in 61900-series | 10 mm |
| Largest outer diameter in 61900-series | 650 mm |
| Width range across 61900-series | 6–78 mm |
| Bore position in 61900-series (smallest first) | 44 of 46 |
| Bore above smallest 61900-series size | 430 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61988 | ISO-INTERCHANGE | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension interchange; ratings above are NTN 2203-3/E values and differ by brand — verify per supplier. |
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
In the 61900-series (diameter series 9 of ISO 15) the last two digits encode the bore: 61988 carries bore code 88 = 440 mm. Outside diameter 600 mm and width 74 mm come from the ISO 15 boundary-dimensions general plan. With no seal suffix the bearing is open: no shields or seals are fitted and lubrication is supplied by the application. For normal-load mounting with a rotating inner ring on a 440 mm shaft, typical catalogue practice is a m6 shaft seat with an H7 housing bore — verify against the actual load direction and magnitude. 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
Common applications
- robotics and automation joints
- lay shafts and idler shafts
- textile machinery
- packaging machinery
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- electrical pitting in VFD-driven motors without grounding protection
- raceway smearing under marginal lubrication at start-up
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.
- 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 61988 units.
- Do not quieten a noisy bearing by preloading it: the 61900-series is a deep-groove design, not angular-contact; axial preload raises temperature and shortens grease life.
- 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 (as printed for some thin-section sizes) denotes a pressed-steel cage, not a seal.
- The 405/615 kN load ratings, 18 kN fatigue load limit Cu and 60000 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6988; this seal/size combination has no counterpart from another catalogue on this site, so the page rests on a single manufacturer source — internal geometry and ratings legitimately differ between brands, so re-verify before substituting in a rated drive.
Frequently asked questions
What are the dimensions of a 61988 bearing?
A 61988 deep-groove ball bearing has a 440 mm bore, 600 mm outer diameter and 74 mm width (17.323 × 23.622 × 2.913 in), per ISO 15 boundary dimensions. It is an open bearing with no seals or shields.
How does the 61988 bore code work?
The last two digits of 61988 are bore code 88, giving 88 × 5 = 440 mm bore. The 600 mm outside diameter and 74 mm width follow the ISO 15 diameter series, not the bore code alone.
What does no suffix on 61988 mean?
A bare 61988 designation means open: no shields or seals, normal CN radial clearance and P0 normal tolerance unless further suffixes are ordered. The application must supply and retain the lubrication.
How does the 61900 compare with other series at the same 440 mm bore?
619 is a thin section one step above 618: 600×74 mm with a 80.0 mm radial section at 440 mm bore; a 6288 on the same bore is substantially larger and more heavily rated.
What is the NTN designation and catalogue data for 61988?
In the NTN Ball and Roller Bearings catalogue (CAT.No.2203-3/E, 2024) this size is listed as 6988 — the open (unsealed) execution, 440×600×74 mm per ISO 15. Quoted values: C 405 kN, C0 615 kN, Cu 18 kN, mass 60000 g. Grease limiting speed 890 rpm. The industry-neutral page spelling 61988 follows the seal-suffix convention used across this site, not NTN order-number spelling.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203-3/E (2024) on 2026-09-25. Read our editorial & correction policy.