51307 bearing: complete specifications & equivalents
The 51307 is a ISO 104 radial bearing sized 35 x 68 x 24 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 35 mm |
| Outer diameter D | 68 mm |
| Width B | 24 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 55.5 kN |
| Basic static load rating C0 | 105 kN |
| Fatigue load limit Pu | 4.75 kN |
| Limiting speed (mechanical) | 2400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 383 g |
| Manufacturer designation | NTN 51307 |
| 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 | 1.378 in |
|---|---|
| Outer diameter D | 2.677 in |
| Width B | 0.945 in |
| ISO bore code | 07 |
| Radial section height (D−d)/2 | 16.5 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) | 3 of 25 |
| Bore above smallest 51300-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51307-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 35×68×24 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 51307 model number is decoded
51307 is an NTN single-direction thrust ball bearing of the heavy-section 51300 thrust family: 35 mm bore, 68 mm outside diameter, 24 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. The designation is 513 is the dimension series (heavy-section 51300 thrust family) plus 07 encodes the 35 mm bore (bore code x 5). NTN prints 55.5 kN axial dynamic and 105 kN axial static for this size and a 4.75 kN fatigue load limit Pu. Choose the heavy-section 51300 thrust family when the shaft carries pure thrust in one direction at moderate speed — vertical shafts are the textbook case. The shaft washer (bore 35 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
- machine-tool tailstock and steady-rest screws
- medium crane hook blocks and slewing jibs
- extruder and mixer thrust housings
- winch and capstan vertical shafts
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
- 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
- In this size class the frequent miss is washer identification: keep the catalogued shaft/housing washer pairing of the 35 mm size together from unpacking to assembly.
- The 513 heavy section buys capacity with a larger 68 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- The 2,400 r/min speed figure assumes the catalogue lubrication state; at high speed the limiting factor is often the minimum load, not the rating table.
- Radial load is the silent killer here: a belt pull or gear force on the same shaft must land on a radial bearing, because 51307 has no radial capacity at all.
- 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 55.5/C0a 105 kN ratings and 4.75 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51307; 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 51307?
51307 is a single-direction thrust ball bearing to ISO 104: 35 mm shaft-washer bore, 68 mm outside diameter, 24 mm stack height (1.378 x 2.677 x 0.945 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 55.5 kN, C0a 105 kN and a 4.75 kN fatigue load limit Pu; the grease limiting speed is 2,400 r/min and the oil rating 3,500 r/min; mass about 383 g.
How is the 51307 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 07 encodes the 35 mm bore (bore code x 5). The 68 mm OD and 24 mm height follow the ISO 104 boundary plan for that series.
Can 51307 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 51307?
At the 2,400 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 51307?
The 35/68/24 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 55.5 kN / C0a 105 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.