51122-NTN bearing: complete specifications & equivalents
The 51122-NTN is a ISO 104 radial bearing sized 110 x 145 x 25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 110 mm |
| Outer diameter D | 145 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 87 kN |
| Basic static load rating C0 | 288 kN |
| Fatigue load limit Pu | 11.5 kN |
| Limiting speed (mechanical) | 1600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1070 g |
| Manufacturer designation | NTN 51122 |
| 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 | 4.331 in |
|---|---|
| Outer diameter D | 5.709 in |
| Width B | 0.984 in |
| ISO bore code | 22 |
| Radial section height (D−d)/2 | 17.5 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) | 21 of 46 |
| Bore above smallest 51100-series size | 100 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51122-NTN model number is decoded
51122 is an NTN single-direction thrust ball bearing of the light-section 51100 thrust family: 110 mm bore, 145 mm outside diameter, 25 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. The designation is 511 is the dimension series (light-section 51100 thrust family) plus 22 encodes the 110 mm bore (bore code x 5). The static margin, C0a 288 kN against Ca 87 kN, is what carries slow oscillating or shock thrust without permanent raceway dents. Selection starts from the load direction: if thrust ever reverses, plan a second thrust bearing (or a double-direction execution) rather than relying on the unloaded raceway. Preload or working clearance must guarantee the minimum axial load at the catalogue speed; a spring or dead-weight arrangement is the usual answer on high-speed vertical shafts.
Typical equipment & failure modes
Common applications
- ship winch and capstan thrust shafts
- crusher main-shaft thrust supports
- large rotary-table and index-table thrust rings
- vertical water-pump and turbine thrust blocks
Known failure patterns
- cage pocket wear and ball skid polish after long running below the minimum axial load, the balls sliding instead of rolling on the washers
- 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
- rapid flaking after radial load was allowed onto the bearing — a single-direction thrust ball bearing carries axial load only
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
- contamination pitting from particles settling on the horizontal housing washer — the classic failure of vertical-shaft grease-lubricated seats
Selection pitfalls — read before you substitute
- At 110 mm bore the washers are heavy enough to sag out of square during assembly — support the stack horizontally where possible and verify face runout before loading.
- The 511 light section is the speed-friendly end of the thrust-ball plan — for the same 110 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Below the minimum axial load the balls skid; the catalogue Ca of 87 kN never saves a bearing that is running too lightly loaded at 1,600 r/min.
- 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.
- Shock thrust above C0a 288 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The Ca 87/C0a 288 kN ratings and 11.5 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51122; 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 51122?
51122 is a single-direction thrust ball bearing to ISO 104: 110 mm shaft-washer bore, 145 mm outside diameter, 25 mm stack height (4.331 x 5.709 x 0.984 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 87 kN, C0a 288 kN and a 11.5 kN fatigue load limit Pu; the grease limiting speed is 1,600 r/min and the oil rating 2,300 r/min; mass about 1070 g.
How is the 51122 designation structured?
511 is the dimension series (light-section 51100 thrust family); 22 encodes the 110 mm bore (bore code x 5). The 145 mm OD and 25 mm height follow the ISO 104 boundary plan for that series.
Can 51122 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 51122?
At the 1,600 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 51122?
The 110/145/25 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 87 kN / C0a 288 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.