51240 bearing: complete specifications & equivalents
The 51240 is a ISO 104 radial bearing sized 200 x 280 x 62 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 200 mm |
| Outer diameter D | 280 mm |
| Width B | 62 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 315 kN |
| Basic static load rating C0 | 1110 kN |
| Fatigue load limit Pu | 32 kN |
| Limiting speed (mechanical) | 700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 11800 g |
| Manufacturer designation | NTN 51240 |
| 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 | 7.874 in |
|---|---|
| Outer diameter D | 11.024 in |
| Width B | 2.441 in |
| ISO bore code | 40 |
| Radial section height (D−d)/2 | 40 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) | 30 of 39 |
| Bore above smallest 51200-series size | 190 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51240 model number is decoded
The medium-section 51200 thrust family entry 51240 stacks a shaft washer, ball-and-cage set and housing washer into 62 mm of height over a 200 mm bore. Two fields make up the code — 512 is the dimension series (medium-section 51200 thrust family) and 40 encodes the 200 mm bore (bore code x 5). Catalogue axial dynamic rating Ca is 315 kN against C0a 1110 kN — a static/dynamic ratio of 3.52 that is the signature of a thrust raceway. Where misalignment between shaft and housing seats is expected, the spherical-seat washer executions (listed separately in the catalogue) absorb what the flat-seat 51240 cannot. Keep the support faces square: a housing face out of perpendicular by a few hundredths over the 280 mm OD already tilts the raceway and concentrates the 1110 kN static capacity on a few balls.
Typical equipment & failure modes
Common applications
- heavy rotary furnace and kiln thrust points
- vertical hydro and pump-turbine thrust supports
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
Known failure patterns
- cage pocket wear and ball skid polish after long running below the minimum axial load, the balls sliding instead of rolling on the washers
- housing-washer rocking on an out-of-square support face, seen as uneven wear around the raceway circle and rising running torque
- rapid flaking after radial load was allowed onto the bearing — a single-direction thrust ball bearing carries axial load only
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
Selection pitfalls — read before you substitute
- For a 200 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 200 mm bore.
- The C0a of 1110 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- Single-direction means exactly that: thrust on 51240 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- Swapping the shaft and housing washers is an easy assembly error on the 200 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- The Ca 315/C0a 1110 kN ratings and 32 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51240; 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 51240?
51240 is a single-direction thrust ball bearing to ISO 104: 200 mm shaft-washer bore, 280 mm outside diameter, 62 mm stack height (7.874 x 11.024 x 2.441 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 315 kN, C0a 1110 kN and a 32 kN fatigue load limit Pu; the grease limiting speed is 700 r/min and the oil rating 990 r/min; mass about 11800 g.
How is the 51240 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 40 encodes the 200 mm bore (bore code x 5). The 280 mm OD and 62 mm height follow the ISO 104 boundary plan for that series.
Can 51240 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 51240?
At the 700 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 51240?
The 200/280/62 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 315 kN / C0a 1110 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.