51188 bearing: complete specifications & equivalents
The 51188 is a ISO 104 radial bearing sized 440 x 540 x 80 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 | 80 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 515 kN |
| Basic static load rating C0 | 2850 kN |
| Fatigue load limit Pu | 58 kN |
| Limiting speed (mechanical) | 400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 40000 g |
| Manufacturer designation | NTN 51188 |
| Standard | ISO 104 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); 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 & 51100-series range
| Bore d | 17.323 in |
|---|---|
| Outer diameter D | 21.26 in |
| Width B | 3.15 in |
| ISO bore code | 88 |
| Radial section height (D−d)/2 | 50 mm |
| Smallest bore in 51100-series | 10 mm |
| Largest outer diameter in 51100-series | 640 mm |
| Width range across 51100-series | 9–85 mm |
| Bore position in 51100-series (smallest first) | 42 of 46 |
| Bore above smallest 51100-series size | 430 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51188 model number is decoded
51188 is an NTN single-direction thrust ball bearing of the light-section 51100 thrust family: 440 mm bore, 540 mm outside diameter, 80 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. NTN builds the number from 511 is the dimension series (light-section 51100 thrust family); 88 encodes the 440 mm bore (bore code x 5). NTN prints 515 kN axial dynamic and 2850 kN axial static for this size and a 58 kN fatigue load limit Pu. The 440/540/80 envelope follows ISO 104, so dimensional interchange holds between makers — raceway osculation and ratings do not automatically follow. The shaft washer (bore 440 mm, tight on the shaft) and the housing washer (slightly looser bore) are not interchangeable — check the catalogue bore codes before pressing anything on.
Typical equipment & failure modes
Common applications
- heavy rotary furnace and kiln thrust points
- vertical hydro and pump-turbine thrust supports
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
Known failure patterns
- ball and raceway smearing from gyroscopic spin when the bearing runs fast under too little axial load — the minimum-load rule exists exactly for this
- fretting between shaft washer and shaft when the seat is cut loose — the washer creeps, the centre line shifts and the balls start running off-track
- early fatigue from thrust reversal hammering the unloaded raceway, because the bearing has no contact surfaces for the opposite direction
- contamination pitting from particles settling on the horizontal housing washer — the classic failure of vertical-shaft grease-lubricated seats
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
Selection pitfalls — read before you substitute
- For a 440 mm bore thrust bearing, the seating surfaces and oil supply decide service life; at this size a field-improvised housing is the usual root cause behind "premature" failures.
- The 511 light section is the speed-friendly end of the thrust-ball plan — for the same 440 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Never substitute a double-direction bearing drawing part-for-part: the single-direction 51188 stack height of 80 mm and washer set differ from the double-direction execution.
- Swapping the shaft and housing washers is an easy assembly error on the 440 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- Do not reuse a thrust bearing to "absorb" shaft thermal growth — the bearing clamps axially, so growth must be handled on the radial-bearing side of the arrangement.
- The Ca 515/C0a 2850 kN ratings and 58 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51188; raceway geometry legitimately differs between manufacturers, so re-verify ratings and washer identification before substituting another make.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 51188?
51188 is a single-direction thrust ball bearing to ISO 104: 440 mm shaft-washer bore, 540 mm outside diameter, 80 mm stack height (17.323 x 21.26 x 3.15 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 515 kN, C0a 2850 kN and a 58 kN fatigue load limit Pu; the grease limiting speed is 400 r/min and the oil rating 580 r/min; mass about 40000 g.
How is the 51188 designation structured?
511 is the dimension series (light-section 51100 thrust family); 88 encodes the 440 mm bore (bore code x 5). The 540 mm OD and 80 mm height follow the ISO 104 boundary plan for that series.
Can 51188 carry radial load or reversing thrust?
No. The raceways contact the balls at 90 deg to the shaft, so the rating is purely axial and single-direction. Radial load must be carried by a separate radial bearing, and reversing thrust needs a second thrust bearing or a double-direction execution.
Why does NTN specify a minimum axial load for 51188?
At the 400 r/min class speed, centrifugal and gyroscopic effects make an under-loaded ball set skid and smear instead of roll. The catalogue minimum-load formula gives the axial preload — from the machine weight, springs or a dead-weight — that keeps the contact rolling.
What should be checked before substituting another make for 51188?
The 440/540/80 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 515 kN / C0a 2850 kN, the speed figures and the shaft/housing washer identification against the donor catalogue.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.