51306 bearing: complete specifications & equivalents
The 51306 is a ISO 104 radial bearing sized 30 x 60 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 30 mm |
| Outer diameter D | 60 mm |
| Width B | 21 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 43 kN |
| Basic static load rating C0 | 86 kN |
| Fatigue load limit Pu | 3.1 kN |
| Limiting speed (mechanical) | 2800 rpm |
| Mass | 269 g |
| Manufacturer designation | 51306 |
| 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 & 51300-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.362 in |
| Width B | 0.827 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 15 mm |
| Smallest bore in 51300-series | 25 mm |
| Largest outer diameter in 51300-series | 170 mm |
| Width range across 51300-series | 18–55 mm |
| Bore position in 51300-series (smallest first) | 2 of 15 |
| Bore above smallest 51300-series size | 5 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51306 model number is decoded
In the 51300-series (ISO 104 dimension series) the leading digits 513 mark a single-direction thrust ball bearing and the last two digits encode the bore: 51306 carries bore code 06 = 30 mm. The ISO 104 boundary dimensions are 30 mm bore, 60 mm outside diameter and 21 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
- false brinelling from vibration while the shaft is stationary
- smearing or scoring from marginal lubrication at start-up
- raceway indentation from static overload or improper mounting force
Selection pitfalls — read before you substitute
- At a 30 mm bore, check shaft shoulder runout before fitting 51306; a skewed shoulder tilts the shaft washer and concentrates load on a few balls.
- The 513xx medium section gains rating at 30 mm bore through a larger 60 mm OD and 21 mm height; the heavier assembly also trades away some speed versus a 512xx.
- The 21 mm height includes both washers and the cage; verify the axial space in the housing before specifying 51306.
- The shaft washer (bore 30 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 51306 thrust ball bearing?
A 51306 thrust ball bearing has a 30 mm bore, 60 mm outside diameter and 21 mm height, per ISO 104 boundary dimensions. It consists of a shaft washer, housing washer and ball cage assembly.
How does the 51306 bore code work?
The last two digits of 51306 are bore code 06, giving 06 × 5 = 30 mm bore. The 60 mm outside diameter and 21 mm height follow the ISO 104 dimension series, not the bore code alone.
Can a 51306 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 51300 compare with other thrust series at the same 30 mm bore?
The 513xx is the medium section: 60×21 mm, 15.0 mm radial section at 30 mm bore, carrying more load than a 512xx but needing a larger housing bore and giving up some speed.
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.