51104 bearing: complete specifications & equivalents
The 51104 is a ISO 104 radial bearing sized 20 x 35 x 10 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 20 mm |
| Outer diameter D | 35 mm |
| Width B | 10 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 14.2 kN |
| Basic static load rating C0 | 24.7 kN |
| Fatigue load limit Pu | 1.12 kN |
| Limiting speed (mechanical) | 5200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 40 g |
| Manufacturer designation | NTN 51104 |
| 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 | 0.787 in |
|---|---|
| Outer diameter D | 1.378 in |
| Width B | 0.394 in |
| ISO bore code | 04 |
| Radial section height (D−d)/2 | 7.5 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) | 5 of 46 |
| Bore above smallest 51100-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51104-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 20×35×10 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
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 51104 model number is decoded
51104 is an NTN single-direction thrust ball bearing of the light-section 51100 thrust family: 20 mm bore, 35 mm outside diameter, 10 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. NTN builds the number from 511 is the dimension series (light-section 51100 thrust family); 04 encodes the 20 mm bore (bore code x 5). Catalogue axial dynamic rating Ca is 14.2 kN against C0a 24.7 kN — a static/dynamic ratio of 1.74 that is the signature of a thrust raceway. 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 14.2 kN is ever approached. The shaft washer (bore 20 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
- food-machine vertical auger shafts
- laboratory centrifuge and mixer thrust ends
- small vertical pump and agitator thrust positions
- bench drill-press and tapping-machine spindles
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
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
Selection pitfalls — read before you substitute
- Small thrust washers of 20 mm bore bend if the shaft shoulder is rough — check burrs before seating, and never press on the housing washer to drive the shaft washer home.
- The 511 light section is the speed-friendly end of the thrust-ball plan — for the same 20 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- 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.
- 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.
- Swapping the shaft and housing washers is an easy assembly error on the 20 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- The Ca 14.2/C0a 24.7 kN ratings and 1.12 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51104; 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 51104?
51104 is a single-direction thrust ball bearing to ISO 104: 20 mm shaft-washer bore, 35 mm outside diameter, 10 mm stack height (0.787 x 1.378 x 0.394 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 14.2 kN, C0a 24.7 kN and a 1.12 kN fatigue load limit Pu; the grease limiting speed is 5,200 r/min and the oil rating 7,500 r/min; mass about 40 g.
How is the 51104 designation structured?
511 is the dimension series (light-section 51100 thrust family); 04 encodes the 20 mm bore (bore code x 5). The 35 mm OD and 10 mm height follow the ISO 104 boundary plan for that series.
Can 51104 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 51104?
At the 5,200 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 51104?
The 20/35/10 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 14.2 kN / C0a 24.7 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.