51212 bearing: complete specifications & equivalents
The 51212 is a ISO 104 radial bearing sized 60 x 95 x 26 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 60 mm |
| Outer diameter D | 95 mm |
| Width B | 26 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 73.5 kN |
| Basic static load rating C0 | 179 kN |
| Fatigue load limit Pu | 8.05 kN |
| Limiting speed (mechanical) | 2000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 676 g |
| Manufacturer designation | NTN 51212 |
| 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 | 2.362 in |
|---|---|
| Outer diameter D | 3.74 in |
| Width B | 1.024 in |
| ISO bore code | 12 |
| Radial section height (D−d)/2 | 17.5 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) | 13 of 39 |
| Bore above smallest 51200-series size | 50 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51212-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 60×95×26 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 51212 model number is decoded
The medium-section 51200 thrust family entry 51212 stacks a shaft washer, ball-and-cage set and housing washer into 26 mm of height over a 60 mm bore. Decoding 51212: 512 is the dimension series (medium-section 51200 thrust family), with 12 encodes the 60 mm bore (bore code x 5). Catalogue mass is about 676 g for the full washer-and-cage stack. The 60/95/26 envelope follows ISO 104, so dimensional interchange holds between makers — raceway osculation and ratings do not automatically follow. The housing washer needs radial freedom in its seat so the bearing can centre itself; clamping it radially defeats the self-centring the loose fit is designed to give.
Typical equipment & failure modes
Common applications
- vertical water-pump and turbine thrust blocks
- large crane hook and swivel assemblies
- rolling-mill screwdown and adjustment screws
- heavy press and forging-machine thrust seats
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
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
Selection pitfalls — read before you substitute
- At 60 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 512 medium section is the default choice: balanced height and capacity for general vertical-shaft duty at 60 mm bore.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- The C0a of 179 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- The 2,000 r/min speed figure assumes the catalogue lubrication state; at high speed the limiting factor is often the minimum load, not the rating table.
- The Ca 73.5/C0a 179 kN ratings and 8.05 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51212; 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 51212?
51212 is a single-direction thrust ball bearing to ISO 104: 60 mm shaft-washer bore, 95 mm outside diameter, 26 mm stack height (2.362 x 3.74 x 1.024 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 73.5 kN, C0a 179 kN and a 8.05 kN fatigue load limit Pu; the grease limiting speed is 2,000 r/min and the oil rating 2,800 r/min; mass about 676 g.
How is the 51212 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 12 encodes the 60 mm bore (bore code x 5). The 95 mm OD and 26 mm height follow the ISO 104 boundary plan for that series.
Can 51212 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 51212?
At the 2,000 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 51212?
The 60/95/26 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 73.5 kN / C0a 179 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.