51128-NTN bearing: complete specifications & equivalents
The 51128-NTN is a ISO 104 radial bearing sized 140 x 180 x 31 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 140 mm |
| Outer diameter D | 180 mm |
| Width B | 31 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 107 kN |
| Basic static load rating C0 | 375 kN |
| Fatigue load limit Pu | 13.4 kN |
| Limiting speed (mechanical) | 1300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1900 g |
| Manufacturer designation | NTN 51128 |
| 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 | 5.512 in |
|---|---|
| Outer diameter D | 7.087 in |
| Width B | 1.22 in |
| ISO bore code | 28 |
| Radial section height (D−d)/2 | 20 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) | 24 of 46 |
| Bore above smallest 51100-series size | 130 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51128-NTN model number is decoded
51128 is an NTN single-direction thrust ball bearing of the light-section 51100 thrust family: 140 mm bore, 180 mm outside diameter, 31 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); 28 encodes the 140 mm bore (bore code x 5). NTN prints 107 kN axial dynamic and 375 kN axial static for this size and a 13.4 kN fatigue load limit Pu. The 140/180/31 envelope follows ISO 104, so dimensional interchange holds between makers — raceway osculation and ratings do not automatically follow. The housing washer needs radial freedom in its seat so the bearing can centre itself; clamping it radially defeats the self-centring the loose fit is designed to give.
Typical equipment & failure modes
Common applications
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
- bulk-handler stacker/reclaimer thrust pivots
- heavy rotary furnace and kiln thrust points
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
- housing-washer rocking on an out-of-square support face, seen as uneven wear around the raceway circle and rising running torque
- rapid flaking after radial load was allowed onto the bearing — a single-direction thrust ball bearing carries axial load only
- 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 140 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 140 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Grease in a horizontal-washer seat stays only if the housing is designed to hold it; open vertical arrangements need an oil bath or a grease-retaining cover.
- Never substitute a double-direction bearing drawing part-for-part: the single-direction 51128 stack height of 31 mm and washer set differ from the double-direction execution.
- 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 107/C0a 375 kN ratings and 13.4 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51128; 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 51128?
51128 is a single-direction thrust ball bearing to ISO 104: 140 mm shaft-washer bore, 180 mm outside diameter, 31 mm stack height (5.512 x 7.087 x 1.22 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 107 kN, C0a 375 kN and a 13.4 kN fatigue load limit Pu; the grease limiting speed is 1,300 r/min and the oil rating 1,800 r/min; mass about 1900 g.
How is the 51128 designation structured?
511 is the dimension series (light-section 51100 thrust family); 28 encodes the 140 mm bore (bore code x 5). The 180 mm OD and 31 mm height follow the ISO 104 boundary plan for that series.
Can 51128 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 51128?
At the 1,300 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 51128?
The 140/180/31 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 107 kN / C0a 375 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.