51148 bearing: complete specifications & equivalents
The 51148 is a ISO 104 radial bearing sized 240 x 300 x 45 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 240 mm |
| Outer diameter D | 300 mm |
| Width B | 45 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 228 kN |
| Basic static load rating C0 | 935 kN |
| Fatigue load limit Pu | 25.6 kN |
| Limiting speed (mechanical) | 780 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 6870 g |
| Manufacturer designation | NTN 51148 |
| 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 & 51100-series range
| Bore d | 9.449 in |
|---|---|
| Outer diameter D | 11.811 in |
| Width B | 1.772 in |
| ISO bore code | 48 |
| Radial section height (D−d)/2 | 30 mm |
| Smallest bore in 51100-series | 10 mm |
| Largest outer diameter in 51100-series | 640 mm |
| Width range across 51100-series | 9–85 mm |
| Bore position in 51100-series (smallest first) | 32 of 46 |
| Bore above smallest 51100-series size | 230 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51148 model number is decoded
NTN 51148 belongs to the light-section 51100 thrust family of single-direction thrust ball bearings: 240 / 300 / 45 mm (shaft bore / OD / height). Reading the code: 511 is the dimension series (light-section 51100 thrust family), and 48 encodes the 240 mm bore (bore code x 5). Flat-seat washers make the bearing tolerant of simple housings but demand square faces: the whole 228 kN rating assumes the load arrives truly axial. Within the thrust-ball plan, 511 is the light section and 514 the heaviest for a given bore; moving up a series raises the C0a from 935 kN class figures at the cost of OD and height. The shaft washer (bore 240 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
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
- bulk-handler stacker/reclaimer thrust pivots
- heavy rotary furnace and kiln thrust points
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
- rapid flaking after radial load was allowed onto the bearing — a single-direction thrust ball bearing carries axial load only
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
- 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 240 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 511 light section is the speed-friendly end of the thrust-ball plan — for the same 240 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Single-direction means exactly that: thrust on 51148 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- Do not reuse a thrust bearing to "absorb" shaft thermal growth — the bearing clamps axially, so growth must be handled on the radial-bearing side of the arrangement.
- Never substitute a double-direction bearing drawing part-for-part: the single-direction 51148 stack height of 45 mm and washer set differ from the double-direction execution.
- The Ca 228/C0a 935 kN ratings and 25.6 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51148; 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 51148?
51148 is a single-direction thrust ball bearing to ISO 104: 240 mm shaft-washer bore, 300 mm outside diameter, 45 mm stack height (9.449 x 11.811 x 1.772 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 228 kN, C0a 935 kN and a 25.6 kN fatigue load limit Pu; the grease limiting speed is 780 r/min and the oil rating 1,100 r/min; mass about 6870 g.
How is the 51148 designation structured?
511 is the dimension series (light-section 51100 thrust family); 48 encodes the 240 mm bore (bore code x 5). The 300 mm OD and 45 mm height follow the ISO 104 boundary plan for that series.
Can 51148 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 51148?
At the 780 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 51148?
The 240/300/45 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 228 kN / C0a 935 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.