51310 bearing: complete specifications & equivalents
The 51310 is a ISO 104 radial bearing sized 50 x 95 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 | 50 mm |
| Outer diameter D | 95 mm |
| Width B | 31 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 96.5 kN |
| Basic static load rating C0 | 202 kN |
| Fatigue load limit Pu | 9.1 kN |
| Limiting speed (mechanical) | 1800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 951 g |
| Manufacturer designation | NTN 51310 |
| 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 & 51300-series range
| Bore d | 1.969 in |
|---|---|
| Outer diameter D | 3.74 in |
| Width B | 1.22 in |
| ISO bore code | 10 |
| Radial section height (D−d)/2 | 22.5 mm |
| Smallest bore in 51300-series | 25 mm |
| Largest outer diameter in 51300-series | 340 mm |
| Width range across 51300-series | 18–110 mm |
| Bore position in 51300-series (smallest first) | 6 of 25 |
| Bore above smallest 51300-series size | 25 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51310-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 50×95×31 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
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 51310 model number is decoded
The heavy-section 51300 thrust family entry 51310 stacks a shaft washer, ball-and-cage set and housing washer into 31 mm of height over a 50 mm bore. The designation is 513 is the dimension series (heavy-section 51300 thrust family) plus 10 encodes the 50 mm bore (bore code x 5). With Ca 96.5 kN and C0a 202 kN, each mm of shaft bore carries about 1.93 kN of dynamic axial rating. Size selection ends with the minimum-load check: at the 1,800 r/min class speed, the balls need a defined axial preload to keep rolling instead of skidding. On a vertical shaft, pack grease between the washers and plan a relubrication path — centrifugal effect drives grease outward and the track runs dry without it.
Typical equipment & failure modes
Common applications
- medium crane hook blocks and slewing jibs
- extruder and mixer thrust housings
- winch and capstan vertical shafts
- press and punch-machine thrust seats
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
- 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
- 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
- In this size class the frequent miss is washer identification: keep the catalogued shaft/housing washer pairing of the 50 mm size together from unpacking to assembly.
- The 513 heavy section buys capacity with a larger 95 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- Below the minimum axial load the balls skid; the catalogue Ca of 96.5 kN never saves a bearing that is running too lightly loaded at 1,800 r/min.
- 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.
- 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.
- The Ca 96.5/C0a 202 kN ratings and 9.1 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51310; 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 51310?
51310 is a single-direction thrust ball bearing to ISO 104: 50 mm shaft-washer bore, 95 mm outside diameter, 31 mm stack height (1.969 x 3.74 x 1.22 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 96.5 kN, C0a 202 kN and a 9.1 kN fatigue load limit Pu; the grease limiting speed is 1,800 r/min and the oil rating 2,600 r/min; mass about 951 g.
How is the 51310 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 10 encodes the 50 mm bore (bore code x 5). The 95 mm OD and 31 mm height follow the ISO 104 boundary plan for that series.
Can 51310 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 51310?
At the 1,800 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 51310?
The 50/95/31 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 96.5 kN / C0a 202 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.