51408 bearing: complete specifications & equivalents
The 51408 is a ISO 104 radial bearing sized 40 x 90 x 36 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 36 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 112 kN |
| Basic static load rating C0 | 205 kN |
| Fatigue load limit Pu | 9.25 kN |
| Limiting speed (mechanical) | 1700 rpm |
| Mass | 1080 g |
| Manufacturer designation | 51408 |
| 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 & 51400-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 1.417 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 51400-series | 25 mm |
| Largest outer diameter in 51400-series | 210 mm |
| Width range across 51400-series | 24–85 mm |
| Bore position in 51400-series (smallest first) | 4 of 15 |
| Bore above smallest 51400-series size | 15 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51408 model number is decoded
In the 51400-series (ISO 104 dimension series) the leading digits 514 mark a single-direction thrust ball bearing and the last two digits encode the bore: 51408 carries bore code 08 = 40 mm. The ISO 104 boundary dimensions are 40 mm bore, 90 mm outside diameter and 36 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
- agricultural equipment spindle thrust
- industrial fan axial restraint
- electric motor axial positioning
- pump and compressor thrust support
Known failure patterns
- cage wear or fracture from sustained vibration or shock loading
- false brinelling from vibration while the shaft is stationary
- smearing or scoring from marginal lubrication at start-up
Selection pitfalls — read before you substitute
- At a 40 mm bore, check shaft shoulder runout before fitting 51408; a skewed shoulder tilts the shaft washer and concentrates load on a few balls.
- The 514xx heavy section at 40 mm bore (90 mm OD) is built for high-load, lower-speed duty; specifying it in a high-rpm application gives excess heat and short grease life — use 511/512 there.
- The 36 mm height includes both washers and the cage; verify the axial space in the housing before specifying 51408.
- Do not use a thrust ball bearing for combined radial-axial loads — pair it with a radial bearing (deep-groove or spherical roller) for the radial component.
Frequently asked questions
What are the dimensions of a 51408 thrust ball bearing?
A 51408 thrust ball bearing has a 40 mm bore, 90 mm outside diameter and 36 mm height, per ISO 104 boundary dimensions. It consists of a shaft washer, housing washer and ball cage assembly.
How does the 51408 bore code work?
The last two digits of 51408 are bore code 08, giving 08 × 5 = 40 mm bore. The 90 mm outside diameter and 36 mm height follow the ISO 104 dimension series, not the bore code alone.
Can a 51408 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 51400 compare with other thrust series at the same 40 mm bore?
The 514xx is the heavy section: 90×36 mm, 25.0 mm radial section at 40 mm bore — the highest-capacity single-direction thrust option here, aimed at lower-speed, high-load shafts.
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.