51311 bearing: complete specifications & equivalents
The 51311 is a ISO 104 radial bearing sized 55 x 105 x 35 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 55 mm |
| Outer diameter D | 105 mm |
| Width B | 35 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 119 kN |
| Basic static load rating C0 | 246 kN |
| Fatigue load limit Pu | 11.1 kN |
| Limiting speed (mechanical) | 1600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1290 g |
| Manufacturer designation | NTN 51311 |
| 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 | 2.165 in |
|---|---|
| Outer diameter D | 4.134 in |
| Width B | 1.378 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 25 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) | 7 of 25 |
| Bore above smallest 51300-series size | 30 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51311-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 55×105×35 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 51311 model number is decoded
At 55 x 105 x 35 mm, NTN 51311 sits in the heavy-section 51300 thrust family of the single-direction thrust programme. Reading the code: 513 is the dimension series (heavy-section 51300 thrust family), and 11 encodes the 55 mm bore (bore code x 5). Because the contact points run at 90 deg to the shaft, none of the rating is available for radial load — not even incidentally. Within the thrust-ball plan, 511 is the light section and 514 the heaviest for a given bore; moving up a series raises the C0a from 246 kN class figures at the cost of OD and height. The shaft washer (bore 55 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
- winch and capstan vertical shafts
- press and punch-machine thrust seats
- conveyor vertical-drive thrust positions
- vertical motor and pump thrust shoes
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
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
- edge loading from a shaft washer mounted off-centre, cutting the contact ellipse short at one side of the track
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 55 mm size together from unpacking to assembly.
- The 513 heavy section buys capacity with a larger 105 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- 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 C0a of 246 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- Single-direction means exactly that: thrust on 51311 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- The Ca 119/C0a 246 kN ratings and 11.1 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51311; 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 51311?
51311 is a single-direction thrust ball bearing to ISO 104: 55 mm shaft-washer bore, 105 mm outside diameter, 35 mm stack height (2.165 x 4.134 x 1.378 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 119 kN, C0a 246 kN and a 11.1 kN fatigue load limit Pu; the grease limiting speed is 1,600 r/min and the oil rating 2,300 r/min; mass about 1290 g.
How is the 51311 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 11 encodes the 55 mm bore (bore code x 5). The 105 mm OD and 35 mm height follow the ISO 104 boundary plan for that series.
Can 51311 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 51311?
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 51311?
The 55/105/35 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 119 kN / C0a 246 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.