51260 bearing: complete specifications & equivalents
The 51260 is a ISO 104 radial bearing sized 300 x 420 x 95 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 300 mm |
| Outer diameter D | 420 mm |
| Width B | 95 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 590 kN |
| Basic static load rating C0 | 2680 kN |
| Fatigue load limit Pu | 63.5 kN |
| Limiting speed (mechanical) | 440 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 40600 g |
| Manufacturer designation | NTN 51260 |
| 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 | 11.811 in |
|---|---|
| Outer diameter D | 16.535 in |
| Width B | 3.74 in |
| ISO bore code | 60 |
| Radial section height (D−d)/2 | 60 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) | 35 of 39 |
| Bore above smallest 51200-series size | 290 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51260 model number is decoded
NTN 51260 belongs to the medium-section 51200 thrust family of single-direction thrust ball bearings: 300 / 420 / 95 mm (shaft bore / OD / height). Reading the code: 512 is the dimension series (medium-section 51200 thrust family), and 60 encodes the 300 mm bore (bore code x 5). The static margin, C0a 2680 kN against Ca 590 kN, is what carries slow oscillating or shock thrust without permanent raceway dents. The 300/420/95 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
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
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
- edge loading from a shaft washer mounted off-centre, cutting the contact ellipse short at one side of the track
- 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 300 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 300 mm bore.
- Never substitute a double-direction bearing drawing part-for-part: the single-direction 51260 stack height of 95 mm and washer set differ from the double-direction execution.
- Shock thrust above C0a 2680 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- Shock thrust above C0a 2680 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The Ca 590/C0a 2680 kN ratings and 63.5 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51260; 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 51260?
51260 is a single-direction thrust ball bearing to ISO 104: 300 mm shaft-washer bore, 420 mm outside diameter, 95 mm stack height (11.811 x 16.535 x 3.74 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 590 kN, C0a 2680 kN and a 63.5 kN fatigue load limit Pu; the grease limiting speed is 440 r/min and the oil rating 630 r/min; mass about 40600 g.
How is the 51260 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 60 encodes the 300 mm bore (bore code x 5). The 420 mm OD and 95 mm height follow the ISO 104 boundary plan for that series.
Can 51260 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 51260?
At the 440 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 51260?
The 300/420/95 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 590 kN / C0a 2680 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.