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 |
| Seal / shield | open |
| Basic dynamic load rating C | 10.3 kN |
| Basic static load rating C0 | 15.4 kN |
| Fatigue load limit Pu | 0.695 kN |
| Limiting speed (mechanical) | 6400 rpm |
| Mass | 23 g |
| Manufacturer designation | 51101 |
| Standard | ISO 104 |
| Catalog version | CAT. No. 2203-3/E 2024 |
| Last verified | 2026-09-25 |
Source: catalog reference (CAT. No. 2203-3/E 2024) · extracted 2026-09-25
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (CAT. No. 2203-3/E 2024); 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 | 135 mm |
| Width range across 51100-series | 9–25 mm |
| Bore position in 51100-series (smallest first) | 2 of 20 |
| Bore above smallest 51100-series size | 2 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51101 model number is decoded
In the 51100-series (ISO 104 dimension series) the leading digits 511 mark a single-direction thrust ball bearing and the last two digits encode the bore: 51101 carries bore code 01 = 12 mm. The ISO 104 boundary dimensions are 12 mm bore, 26 mm outside diameter and 9 mm height. Two flat washers (shaft and housing) and a ball cage assembly allow the bearing to carry pure axial load in one direction while accommodating minor misalignment.
Typical equipment & failure modes
Common applications
- small electric motor axial positioning
- appliance gearbox thrust washers
- small pump axial load support
- instrument and office machine spindles
Known failure patterns
- rolling-contact fatigue spalling after the rated L10 life is exceeded
- cage wear or fracture from sustained vibration or shock loading
- false brinelling from vibration while the shaft is stationary
Selection pitfalls — read before you substitute
- At a 12 mm bore, thrust ball washers are thin and easily distorted; press the shaft washer on with a proper sleeve — never hammer it or the raceway will brinell.
- The 511xx light section at 12 mm bore uses a smaller 26 mm OD than a 512xx; load ratings are lower, so do not replace a failed 512-series bearing with a 511-series without re-rating the load.
- Thrust ball bearings carry axial load only — never apply radial load to 51101; the flat washers will skid and score.
- The shaft washer (bore 12 mm) must be a tight fit on the shaft; the housing washer should be loose in the housing to allow self-alignment.
Frequently asked questions
What are the dimensions of a 51101 thrust ball bearing?
A 51101 thrust ball bearing has a 12 mm bore, 26 mm outside diameter and 9 mm height, per ISO 104 boundary dimensions. It consists of a shaft washer, housing washer and ball cage assembly.
How does the 51101 bore code work?
The last two digits of 51101 are bore code 01, giving 01 × 5 = 12 mm bore. The 26 mm outside diameter and 9 mm height follow the ISO 104 dimension series, not the bore code alone.
Can a 51101 thrust ball bearing carry radial load?
No. Single-direction thrust ball bearings carry axial load only. Any radial component must be supported by a separate radial bearing (deep-groove, cylindrical roller or spherical roller).
How does the 51100 compare with other thrust series at the same 12 mm bore?
The 511xx is the light section: 26×9 mm with a 7.0 mm radial section at 12 mm bore — below 512/513/514 in load capacity, for light axial loads in compact spaces.
Reviewed & verified by the MPN Base engineering desk against source catalog CAT. No. 2203-3/E 2024 on 2026-09-25. Read our editorial & correction policy.