51326 bearing: complete specifications & equivalents
The 51326 is a ISO 104 radial bearing sized 130 x 225 x 75 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 130 mm |
| Outer diameter D | 225 mm |
| Width B | 75 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 330 kN |
| Basic static load rating C0 | 960 kN |
| Fatigue load limit Pu | 32.5 kN |
| Limiting speed (mechanical) | 720 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 12700 g |
| Manufacturer designation | NTN 51326 |
| 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 | 5.118 in |
|---|---|
| Outer diameter D | 8.858 in |
| Width B | 2.953 in |
| ISO bore code | 26 |
| Radial section height (D−d)/2 | 47.5 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) | 18 of 25 |
| Bore above smallest 51300-series size | 105 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51326-M | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 130×225×75 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 51326 model number is decoded
51326 is the 130 mm member of NTN's heavy-section 51300 thrust family: 225 mm across the washers, 75 mm tall. Decoding 51326: 513 is the dimension series (heavy-section 51300 thrust family), with 26 encodes the 130 mm bore (bore code x 5). The washer section here is 47.5 mm of radial height, and the catalogue couples it with Ca 330 kN / C0a 960 kN. 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 960 kN class figures at the cost of OD and height. 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
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
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
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
Selection pitfalls — read before you substitute
- For a 130 mm bore thrust bearing, the seating surfaces and oil supply decide service life; at this size a field-improvised housing is the usual root cause behind "premature" failures.
- The 513 heavy section buys capacity with a larger 225 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- Single-direction means exactly that: thrust on 51326 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- Shock thrust above C0a 960 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The C0a of 960 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- The Ca 330/C0a 960 kN ratings and 32.5 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51326; 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 51326?
51326 is a single-direction thrust ball bearing to ISO 104: 130 mm shaft-washer bore, 225 mm outside diameter, 75 mm stack height (5.118 x 8.858 x 2.953 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 330 kN, C0a 960 kN and a 32.5 kN fatigue load limit Pu; the grease limiting speed is 720 r/min and the oil rating 1,000 r/min; mass about 12700 g.
How is the 51326 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 26 encodes the 130 mm bore (bore code x 5). The 225 mm OD and 75 mm height follow the ISO 104 boundary plan for that series.
Can 51326 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 51326?
At the 720 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 51326?
The 130/225/75 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 330 kN / C0a 960 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.