51324 bearing: complete specifications & equivalents
The 51324 is a ISO 104 radial bearing sized 120 x 210 x 70 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 120 mm |
| Outer diameter D | 210 mm |
| Width B | 70 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 296 kN |
| Basic static load rating C0 | 805 kN |
| Fatigue load limit Pu | 28.3 kN |
| Limiting speed (mechanical) | 780 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 10800 g |
| Manufacturer designation | NTN 51324 |
| 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 | 4.724 in |
|---|---|
| Outer diameter D | 8.268 in |
| Width B | 2.756 in |
| ISO bore code | 24 |
| Radial section height (D−d)/2 | 45 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) | 17 of 25 |
| Bore above smallest 51300-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51324-M | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 120×210×70 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 51324 model number is decoded
The heavy-section 51300 thrust family entry 51324 stacks a shaft washer, ball-and-cage set and housing washer into 70 mm of height over a 120 mm bore. Reading the code: 513 is the dimension series (heavy-section 51300 thrust family), and 24 encodes the 120 mm bore (bore code x 5). At 70 mm of height the stack is compact for the 120 mm bore class, trading section height for the heavy-section load level. If the duty is high speed with light thrust, check the minimum axial load formula first; a too-large thrust ball bearing fails by skid long before its Ca of 296 kN is ever approached. Preload or working clearance must guarantee the minimum axial load at the catalogue speed; a spring or dead-weight arrangement is the usual answer on high-speed vertical shafts.
Typical equipment & failure modes
Common applications
- large mixer and reactor vertical shafts
- bulk-handler stacker/reclaimer thrust pivots
- heavy rotary furnace and kiln thrust points
- vertical hydro and pump-turbine thrust supports
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
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
- 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
- For a 120 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 210 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- Below the minimum axial load the balls skid; the catalogue Ca of 296 kN never saves a bearing that is running too lightly loaded at 780 r/min.
- The Ca 296/C0a 805 kN ratings and 28.3 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51324; 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 51324?
51324 is a single-direction thrust ball bearing to ISO 104: 120 mm shaft-washer bore, 210 mm outside diameter, 70 mm stack height (4.724 x 8.268 x 2.756 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 296 kN, C0a 805 kN and a 28.3 kN fatigue load limit Pu; the grease limiting speed is 780 r/min and the oil rating 1,100 r/min; mass about 10800 g.
How is the 51324 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 24 encodes the 120 mm bore (bore code x 5). The 210 mm OD and 70 mm height follow the ISO 104 boundary plan for that series.
Can 51324 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 51324?
At the 780 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 51324?
The 120/210/70 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 296 kN / C0a 805 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.