51315 bearing: complete specifications & equivalents
The 51315 is a ISO 104 radial bearing sized 75 x 135 x 44 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 75 mm |
| Outer diameter D | 135 mm |
| Width B | 44 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 171 kN |
| Basic static load rating C0 | 395 kN |
| Fatigue load limit Pu | 17.4 kN |
| Limiting speed (mechanical) | 1300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2610 g |
| Manufacturer designation | NTN 51315 |
| 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 | 2.953 in |
|---|---|
| Outer diameter D | 5.315 in |
| Width B | 1.732 in |
| ISO bore code | 15 |
| Radial section height (D−d)/2 | 30 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) | 11 of 25 |
| Bore above smallest 51300-series size | 50 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51315-SKF | SKF | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
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 51315 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 51315 appears as a heavy-section 51300 thrust family bearing with a 75 mm shaft washer, a 135 mm housing diameter and 44 mm of stack height. The designation is 513 is the dimension series (heavy-section 51300 thrust family) plus 15 encodes the 75 mm bore (bore code x 5). NTN prints 171 kN axial dynamic and 395 kN axial static for this size and a 17.4 kN fatigue load limit Pu. Where misalignment between shaft and housing seats is expected, the spherical-seat washer executions (listed separately in the catalogue) absorb what the flat-seat 51315 cannot. After assembly, rotate under light load and check torque and temperature rise — a thrust ball bearing mounted with the washers swapped runs, but fails fast.
Typical equipment & failure modes
Common applications
- crusher main-shaft thrust supports
- large rotary-table and index-table thrust rings
- vertical water-pump and turbine thrust blocks
- large crane hook and swivel assemblies
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
- 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
- At 75 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 513 heavy section buys capacity with a larger 135 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- Radial load is the silent killer here: a belt pull or gear force on the same shaft must land on a radial bearing, because 51315 has no radial capacity at all.
- Shock thrust above C0a 395 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- 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 171/C0a 395 kN ratings and 17.4 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51315; 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 51315?
51315 is a single-direction thrust ball bearing to ISO 104: 75 mm shaft-washer bore, 135 mm outside diameter, 44 mm stack height (2.953 x 5.315 x 1.732 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 171 kN, C0a 395 kN and a 17.4 kN fatigue load limit Pu; the grease limiting speed is 1,300 r/min and the oil rating 1,800 r/min; mass about 2610 g.
How is the 51315 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 15 encodes the 75 mm bore (bore code x 5). The 135 mm OD and 44 mm height follow the ISO 104 boundary plan for that series.
Can 51315 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 51315?
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 51315?
The 75/135/44 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 171 kN / C0a 395 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.