51406 bearing: complete specifications & equivalents
The 51406 is a ISO 104 radial bearing sized 30 x 70 x 28 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 30 mm |
| Outer diameter D | 70 mm |
| Width B | 28 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 72.5 kN |
| Basic static load rating C0 | 126 kN |
| Fatigue load limit Pu | 5.65 kN |
| Limiting speed (mechanical) | 2200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 516 g |
| Manufacturer designation | NTN 51406 |
| 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 & 51400-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.756 in |
| Width B | 1.102 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 20 mm |
| Smallest bore in 51400-series | 25 mm |
| Largest outer diameter in 51400-series | 300 mm |
| Width range across 51400-series | 24–120 mm |
| Bore position in 51400-series (smallest first) | 2 of 20 |
| Bore above smallest 51400-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51406-SKF | SKF | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
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 51406 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 51406 appears as a extra-heavy 51400 thrust family bearing with a 30 mm shaft washer, a 70 mm housing diameter and 28 mm of stack height. Reading the code: 514 is the dimension series (extra-heavy 51400 thrust family), and 06 encodes the 30 mm bore (bore code x 5). With Ca 72.5 kN and C0a 126 kN, each mm of shaft bore carries about 2.42 kN of dynamic axial rating. For a 30 mm shaft with combined radial-plus-axial load, pair this bearing with a separate radial bearing — the thrust ball bearing must never be asked to carry the radial share. Keep the support faces square: a housing face out of perpendicular by a few hundredths over the 70 mm OD already tilts the raceway and concentrates the 126 kN static capacity on a few balls.
Typical equipment & failure modes
Common applications
- extruder and mixer thrust housings
- winch and capstan vertical shafts
- press and punch-machine thrust seats
- conveyor vertical-drive thrust positions
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
- housing-washer rocking on an out-of-square support face, seen as uneven wear around the raceway circle and rising running torque
- early fatigue from thrust reversal hammering the unloaded raceway, because the bearing has no contact surfaces for the opposite direction
- 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
- In this size class the frequent miss is washer identification: keep the catalogued shaft/housing washer pairing of the 30 mm size together from unpacking to assembly.
- The 514 extra-heavy section is the top of the thrust-ball plan at this bore; beyond it the catalogue moves to spherical roller thrust bearings.
- Single-direction means exactly that: thrust on 51406 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- Below the minimum axial load the balls skid; the catalogue Ca of 72.5 kN never saves a bearing that is running too lightly loaded at 2,200 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.
- The Ca 72.5/C0a 126 kN ratings and 5.65 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51406; 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 51406?
51406 is a single-direction thrust ball bearing to ISO 104: 30 mm shaft-washer bore, 70 mm outside diameter, 28 mm stack height (1.181 x 2.756 x 1.102 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 72.5 kN, C0a 126 kN and a 5.65 kN fatigue load limit Pu; the grease limiting speed is 2,200 r/min and the oil rating 3,200 r/min; mass about 516 g.
How is the 51406 designation structured?
514 is the dimension series (extra-heavy 51400 thrust family); 06 encodes the 30 mm bore (bore code x 5). The 70 mm OD and 28 mm height follow the ISO 104 boundary plan for that series.
Can 51406 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 51406?
At the 2,200 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 51406?
The 30/70/28 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 72.5 kN / C0a 126 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.