61888 bearing: complete specifications & equivalents
The 61888 is a ISO 15 radial bearing sized 440 x 540 x 46 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 | 540 mm |
| Width B | 46 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 292 kN |
| Basic static load rating C0 | 420 kN |
| Fatigue load limit Pu | 12.6 kN |
| Limiting speed (mechanical) | 950 rpm |
| Mass | 22500 g |
| Manufacturer designation | NTN 6888 |
| 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 & 61800-series range
| Bore d | 17.323 in |
|---|---|
| Outer diameter D | 21.26 in |
| Width B | 1.811 in |
| ISO bore code | 88 |
| Radial section height (D−d)/2 | 50 mm |
| Smallest bore in 61800-series | 10 mm |
| Largest outer diameter in 61800-series | 600 mm |
| Width range across 61800-series | 5–56 mm |
| Bore position in 61800-series (smallest first) | 44 of 46 |
| Bore above smallest 61800-series size | 430 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 61888 | 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 61888 model number is decoded
In the 61800-series (diameter series 8 of ISO 15) the last two digits encode the bore: 61888 carries bore code 88 = 440 mm. Outside diameter 540 mm and width 46 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
- space-constrained gearboxes
- clutch and transmission assemblies
- robotics and automation joints
- lay shafts and idler shafts
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- cage damage from operation beyond the limiting speed
- electrical pitting in VFD-driven motors without grounding protection
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 618xx thin section at 440 mm bore has only a 50.0 mm radial section height: it saves space but is highly sensitive to misalignment, shaft deflection and shock loads — verify shaft stiffness before choosing it over a 6288.
- The open 61888 has no lubricant retention: grease escapes and contaminants migrate straight into the 440×540×46 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Open bearings tolerate the highest speeds in the 61800-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 61888 units.
- Deep-groove ball bearings tolerate only minutes of misalignment; if the 540 mm housing cannot be aligned, switch to a self-aligning type rather than shimming 61888.
- The open 61888 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 292/420 kN load ratings, 12.6 kN fatigue load limit Cu and 22500 g mass here are NTN Ball and Roller Bearings CAT.No.2203-3/E figures for 6888; 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 61888 bearing?
A 61888 deep-groove ball bearing has a 440 mm bore, 540 mm outer diameter and 46 mm width (17.323 × 21.26 × 1.811 in), per ISO 15 boundary dimensions. It is an open bearing with no seals or shields.
How does the 61888 bore code work?
The last two digits of 61888 are bore code 88, giving 88 × 5 = 440 mm bore. The 540 mm outside diameter and 46 mm width follow the ISO 15 diameter series, not the bore code alone.
What does no suffix on 61888 mean?
A bare 61888 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 61800 compare with other series at the same 440 mm bore?
618 is an extra-thin section: 540×46 mm, only 50.0 mm radial section at 440 mm bore, far smaller than a 6288, for space-limited layouts at the cost of load rating and misalignment tolerance.
What is the NTN designation and catalogue data for 61888?
In the NTN Ball and Roller Bearings catalogue (CAT.No.2203-3/E, 2024) this size is listed as 6888 — the open (unsealed) execution, 440×540×46 mm per ISO 15. Quoted values: C 292 kN, C0 420 kN, Cu 12.6 kN, mass 22500 g. Grease limiting speed 950 rpm. The industry-neutral page spelling 61888 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.