51230 bearing: complete specifications & equivalents
The 51230 is a ISO 104 radial bearing sized 150 x 215 x 50 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 150 mm |
| Outer diameter D | 215 mm |
| Width B | 50 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 227 kN |
| Basic static load rating C0 | 720 kN |
| Fatigue load limit Pu | 24 kN |
| Limiting speed (mechanical) | 900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 5870 g |
| Manufacturer designation | NTN 51230 |
| 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 & 51200-series range
| Bore d | 5.906 in |
|---|---|
| Outer diameter D | 8.465 in |
| Width B | 1.969 in |
| ISO bore code | 30 |
| Radial section height (D−d)/2 | 32.5 mm |
| Smallest bore in 51200-series | 10 mm |
| Largest outer diameter in 51200-series | 520 mm |
| Width range across 51200-series | 11–112 mm |
| Bore position in 51200-series (smallest first) | 25 of 39 |
| Bore above smallest 51200-series size | 140 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51230 model number is decoded
51230 is an NTN single-direction thrust ball bearing of the medium-section 51200 thrust family: 150 mm bore, 215 mm outside diameter, 50 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. The designation is 512 is the dimension series (medium-section 51200 thrust family) plus 30 encodes the 150 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 720 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
- bulk-handler stacker/reclaimer thrust pivots
- heavy rotary furnace and kiln thrust points
- vertical hydro and pump-turbine thrust supports
- large marine winch and windlass 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
- 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
- For a 150 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 512 medium section is the default choice: balanced height and capacity for general vertical-shaft duty at 150 mm bore.
- The 900 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 51230 has no radial capacity at all.
- Single-direction means exactly that: thrust on 51230 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 227/C0a 720 kN ratings and 24 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51230; 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 51230?
51230 is a single-direction thrust ball bearing to ISO 104: 150 mm shaft-washer bore, 215 mm outside diameter, 50 mm stack height (5.906 x 8.465 x 1.969 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 227 kN, C0a 720 kN and a 24 kN fatigue load limit Pu; the grease limiting speed is 900 r/min and the oil rating 1,300 r/min; mass about 5870 g.
How is the 51230 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 30 encodes the 150 mm bore (bore code x 5). The 215 mm OD and 50 mm height follow the ISO 104 boundary plan for that series.
Can 51230 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 51230?
At the 900 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 51230?
The 150/215/50 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 227 kN / C0a 720 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.