51232 bearing: complete specifications & equivalents
The 51232 is a ISO 104 radial bearing sized 160 x 225 x 51 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 160 mm |
| Outer diameter D | 225 mm |
| Width B | 51 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 223 kN |
| Basic static load rating C0 | 720 kN |
| Fatigue load limit Pu | 23.3 kN |
| Limiting speed (mechanical) | 870 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 6320 g |
| Manufacturer designation | NTN 51232 |
| 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 | 6.299 in |
|---|---|
| Outer diameter D | 8.858 in |
| Width B | 2.008 in |
| ISO bore code | 32 |
| 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) | 26 of 39 |
| Bore above smallest 51200-series size | 150 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51232 model number is decoded
NTN 51232 belongs to the medium-section 51200 thrust family of single-direction thrust ball bearings: 160 / 225 / 51 mm (shaft bore / OD / height). Two fields make up the code — 512 is the dimension series (medium-section 51200 thrust family) and 32 encodes the 160 mm bore (bore code x 5). Catalogue axial dynamic rating Ca is 223 kN against C0a 720 kN — a static/dynamic ratio of 3.23 that is the signature of a thrust raceway. Choose the medium-section 51200 thrust family when the shaft carries pure thrust in one direction at moderate speed — vertical shafts are the textbook case. On a vertical shaft, pack grease between the washers and plan a relubrication path — centrifugal effect drives grease outward and the track runs dry without it.
Typical equipment & failure modes
Common applications
- heavy press and mill screwdown thrust seats
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
- bulk-handler stacker/reclaimer thrust pivots
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
- edge loading from a shaft washer mounted off-centre, cutting the contact ellipse short at one side of the track
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
Selection pitfalls — read before you substitute
- For a 160 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 160 mm bore.
- Radial load is the silent killer here: a belt pull or gear force on the same shaft must land on a radial bearing, because 51232 has no radial capacity at all.
- Swapping the shaft and housing washers is an easy assembly error on the 160 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- Swapping the shaft and housing washers is an easy assembly error on the 160 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- The Ca 223/C0a 720 kN ratings and 23.3 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51232; 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 51232?
51232 is a single-direction thrust ball bearing to ISO 104: 160 mm shaft-washer bore, 225 mm outside diameter, 51 mm stack height (6.299 x 8.858 x 2.008 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 223 kN, C0a 720 kN and a 23.3 kN fatigue load limit Pu; the grease limiting speed is 870 r/min and the oil rating 1,200 r/min; mass about 6320 g.
How is the 51232 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 32 encodes the 160 mm bore (bore code x 5). The 225 mm OD and 51 mm height follow the ISO 104 boundary plan for that series.
Can 51232 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 51232?
At the 870 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 51232?
The 160/225/51 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 223 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.