51244 bearing: complete specifications & equivalents
The 51244 is a ISO 104 radial bearing sized 220 x 300 x 63 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 220 mm |
| Outer diameter D | 300 mm |
| Width B | 63 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 325 kN |
| Basic static load rating C0 | 1210 kN |
| Fatigue load limit Pu | 34 kN |
| Limiting speed (mechanical) | 660 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 13000 g |
| Manufacturer designation | NTN 51244 |
| 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 | 8.661 in |
|---|---|
| Outer diameter D | 11.811 in |
| Width B | 2.48 in |
| ISO bore code | 44 |
| 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) | 31 of 39 |
| Bore above smallest 51200-series size | 210 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51244 model number is decoded
51244 is an NTN single-direction thrust ball bearing of the medium-section 51200 thrust family: 220 mm bore, 300 mm outside diameter, 63 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. Reading the code: 512 is the dimension series (medium-section 51200 thrust family), and 44 encodes the 220 mm bore (bore code x 5). The static margin, C0a 1210 kN against Ca 325 kN, is what carries slow oscillating or shock thrust without permanent raceway dents. Size selection ends with the minimum-load check: at the 660 r/min class speed, the balls need a defined axial preload to keep rolling instead of skidding. The shaft washer (bore 220 mm, tight on the shaft) and the housing washer (slightly looser bore) are not interchangeable — check the catalogue bore codes before pressing anything on.
Typical equipment & failure modes
Common applications
- vertical hydro and pump-turbine thrust supports
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
- crane slew-ring auxiliary thrust positions
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
- 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 220 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 220 mm bore.
- Below the minimum axial load the balls skid; the catalogue Ca of 325 kN never saves a bearing that is running too lightly loaded at 660 r/min.
- Grease in a horizontal-washer seat stays only if the housing is designed to hold it; open vertical arrangements need an oil bath or a grease-retaining cover.
- Shock thrust above C0a 1210 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The Ca 325/C0a 1210 kN ratings and 34 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51244; 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 51244?
51244 is a single-direction thrust ball bearing to ISO 104: 220 mm shaft-washer bore, 300 mm outside diameter, 63 mm stack height (8.661 x 11.811 x 2.48 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 325 kN, C0a 1210 kN and a 34 kN fatigue load limit Pu; the grease limiting speed is 660 r/min and the oil rating 950 r/min; mass about 13000 g.
How is the 51244 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 44 encodes the 220 mm bore (bore code x 5). The 300 mm OD and 63 mm height follow the ISO 104 boundary plan for that series.
Can 51244 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 51244?
At the 660 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 51244?
The 220/300/63 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 325 kN / C0a 1210 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.