51101 bearing: complete specifications & equivalents
The 51101 is a ISO 104 radial bearing sized 12 x 26 x 9 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 12 mm |
| Outer diameter D | 26 mm |
| Width B | 9 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 10.3 kN |
| Basic static load rating C0 | 15.4 kN |
| Fatigue load limit Pu | 0.69 kN |
| Limiting speed (mechanical) | 6400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 23 g |
| Manufacturer designation | NTN 51101 |
| 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 | 0.472 in |
|---|---|
| Outer diameter D | 1.024 in |
| Width B | 0.354 in |
| ISO bore code | 01 |
| Radial section height (D−d)/2 | 7 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) | 2 of 46 |
| Bore above smallest 51100-series size | 2 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51101-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 51101 model number is decoded
At 12 x 26 x 9 mm, NTN 51101 sits in the light-section 51100 thrust family of the single-direction thrust programme. Reading the code: 511 is the dimension series (light-section 51100 thrust family), and the bore code 01 maps to the 12 mm bore by the standard table. With Ca 10.3 kN and C0a 15.4 kN, each mm of shaft bore carries about 0.86 kN of dynamic axial rating. Where misalignment between shaft and housing seats is expected, the spherical-seat washer executions (listed separately in the catalogue) absorb what the flat-seat 51101 cannot. After assembly, rotate under light load and check torque and temperature rise — a thrust ball bearing mounted with the washers swapped runs, but fails fast.
Typical equipment & failure modes
Common applications
- laboratory centrifuge and mixer thrust ends
- small vertical pump and agitator thrust positions
- bench drill-press and tapping-machine spindles
- automotive steering-gear and clutch release points
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
- 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
- Small thrust washers of 12 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 12 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Shock thrust above C0a 15.4 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- Swapping the shaft and housing washers is an easy assembly error on the 12 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- 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 10.3/C0a 15.4 kN ratings and 0.69 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51101; 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 51101?
51101 is a single-direction thrust ball bearing to ISO 104: 12 mm shaft-washer bore, 26 mm outside diameter, 9 mm stack height (0.472 x 1.024 x 0.354 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 10.3 kN, C0a 15.4 kN and a 0.69 kN fatigue load limit Pu; the grease limiting speed is 6,400 r/min and the oil rating 9,200 r/min; mass about 23 g.
How is the 51101 designation structured?
511 is the dimension series (light-section 51100 thrust family); the bore code 01 maps to the 12 mm bore by the standard table. The 26 mm OD and 9 mm height follow the ISO 104 boundary plan for that series.
Can 51101 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 51101?
At the 6,400 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 51101?
The 12/26/9 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 10.3 kN / C0a 15.4 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.