51420 bearing: complete specifications & equivalents
The 51420 is a ISO 104 radial bearing sized 100 x 210 x 85 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 100 mm |
| Outer diameter D | 210 mm |
| Width B | 85 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 370 kN |
| Basic static load rating C0 | 970 kN |
| Fatigue load limit Pu | 35 kN |
| Limiting speed (mechanical) | 710 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 14700 g |
| Manufacturer designation | NTN 51420 |
| 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 | 3.937 in |
|---|---|
| Outer diameter D | 8.268 in |
| Width B | 3.346 in |
| ISO bore code | 20 |
| Radial section height (D−d)/2 | 55 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) | 15 of 20 |
| Bore above smallest 51400-series size | 75 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51420-M | 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 51420 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 51420 appears as a extra-heavy 51400 thrust family bearing with a 100 mm shaft washer, a 210 mm housing diameter and 85 mm of stack height. NTN builds the number from 514 is the dimension series (extra-heavy 51400 thrust family); 20 encodes the 100 mm bore (bore code x 5). The ball-and-cage set is separable from both washers, which is why the mounting order (shaft washer first, then cage, then housing washer) matters. If the duty is high speed with light thrust, check the minimum axial load formula first; a too-large thrust ball bearing fails by skid long before its Ca of 370 kN is ever approached. Preload or working clearance must guarantee the minimum axial load at the catalogue speed; a spring or dead-weight arrangement is the usual answer on high-speed vertical shafts.
Typical equipment & failure modes
Common applications
- vertical water-pump and turbine thrust blocks
- large crane hook and swivel assemblies
- rolling-mill screwdown and adjustment screws
- heavy press and forging-machine thrust seats
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
- contamination pitting from particles settling on the horizontal housing washer — the classic failure of vertical-shaft grease-lubricated seats
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
Selection pitfalls — read before you substitute
- At 100 mm bore the washers are heavy enough to sag out of square during assembly — support the stack horizontally where possible and verify face runout before loading.
- 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.
- 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 C0a of 970 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- Radial load is the silent killer here: a belt pull or gear force on the same shaft must land on a radial bearing, because 51420 has no radial capacity at all.
- The Ca 370/C0a 970 kN ratings and 35 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51420; 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 51420?
51420 is a single-direction thrust ball bearing to ISO 104: 100 mm shaft-washer bore, 210 mm outside diameter, 85 mm stack height (3.937 x 8.268 x 3.346 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 370 kN, C0a 970 kN and a 35 kN fatigue load limit Pu; the grease limiting speed is 710 r/min and the oil rating 1,000 r/min; mass about 14700 g.
How is the 51420 designation structured?
514 is the dimension series (extra-heavy 51400 thrust family); 20 encodes the 100 mm bore (bore code x 5). The 210 mm OD and 85 mm height follow the ISO 104 boundary plan for that series.
Can 51420 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 51420?
At the 710 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 51420?
The 100/210/85 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 370 kN / C0a 970 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.