51115 bearing: complete specifications & equivalents
The 51115 is a ISO 104 radial bearing sized 75 x 100 x 19 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 75 mm |
| Outer diameter D | 100 mm |
| Width B | 19 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 46 kN |
| Basic static load rating C0 | 140 kN |
| Fatigue load limit Pu | 6.45 kN |
| Limiting speed (mechanical) | 2200 rpm |
| Mass | 400 g |
| Manufacturer designation | 51115 |
| 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 | 2.953 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 0.748 in |
| ISO bore code | 15 |
| Radial section height (D−d)/2 | 12.5 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) | 16 of 20 |
| Bore above smallest 51100-series size | 65 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51115 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: 51115 carries bore code 15 = 75 mm. The ISO 104 boundary dimensions are 75 mm bore, 100 mm outside diameter and 19 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
- conveyor and elevator thrust washers
- machine tool spindle axial positioning
- paper mill roll axial restraint
- industrial motor and generator thrust
Known failure patterns
- smearing or scoring from marginal lubrication at start-up
- raceway indentation from static overload or improper mounting force
- washer seat fretting from a loose housing or shaft fit
Selection pitfalls — read before you substitute
- At a 75 mm bore, thermal expansion of the shaft can preload the thrust bearing; verify the housing washer has radial clearance to float and compensate.
- The 511xx light section at 75 mm bore uses a smaller 100 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.
- Minimum axial load is required to prevent ball skidding: at very light loads the balls slide rather than roll, causing smearing and early failure.
- The 19 mm height includes both washers and the cage; verify the axial space in the housing before specifying 51115.
Frequently asked questions
What are the dimensions of a 51115 thrust ball bearing?
A 51115 thrust ball bearing has a 75 mm bore, 100 mm outside diameter and 19 mm height, per ISO 104 boundary dimensions. It consists of a shaft washer, housing washer and ball cage assembly.
How does the 51115 bore code work?
The last two digits of 51115 are bore code 15, giving 15 × 5 = 75 mm bore. The 100 mm outside diameter and 19 mm height follow the ISO 104 dimension series, not the bore code alone.
Can a 51115 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 75 mm bore?
The 511xx is the light section: 100×19 mm with a 12.5 mm radial section at 75 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.