51320 bearing: complete specifications & equivalents
The 51320 is a ISO 104 radial bearing sized 100 x 170 x 55 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 100 mm |
| Outer diameter D | 170 mm |
| Width B | 55 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 237 kN |
| Basic static load rating C0 | 595 kN |
| Fatigue load limit Pu | 25 kN |
| Limiting speed (mechanical) | 990 rpm |
| Mass | 4880 g |
| Manufacturer designation | 51320 |
| 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 | 3.937 in |
|---|---|
| Outer diameter D | 6.693 in |
| Width B | 2.165 in |
| ISO bore code | 20 |
| Radial section height (D−d)/2 | 35 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) | 15 of 15 |
| Bore above smallest 51300-series size | 75 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51320 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: 51320 carries bore code 20 = 100 mm. The ISO 104 boundary dimensions are 100 mm bore, 170 mm outside diameter and 55 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
- crane and hoist drum thrust washers
- steel mill roll axial restraint
- ship propeller shaft thrust support
- mining equipment axial positioning
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
- Mount this 100 mm bore thrust bearing by heating the shaft washer (induction heater, max 120 °C) — never drive it home through the housing washer or balls.
- The 513xx medium section gains rating at 100 mm bore through a larger 170 mm OD and 55 mm height; the heavier assembly also trades away some speed versus a 512xx.
- 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.
- Single-direction thrust ball bearings carry load in one direction only; for bidirectional thrust use a double-direction bearing or two single-direction units back-to-back.
Frequently asked questions
What are the dimensions of a 51320 thrust ball bearing?
A 51320 thrust ball bearing has a 100 mm bore, 170 mm outside diameter and 55 mm height, per ISO 104 boundary dimensions. It consists of a shaft washer, housing washer and ball cage assembly.
How does the 51320 bore code work?
The last two digits of 51320 are bore code 20, giving 20 × 5 = 100 mm bore. The 170 mm outside diameter and 55 mm height follow the ISO 104 dimension series, not the bore code alone.
Can a 51320 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 100 mm bore?
The 513xx is the medium section: 170×55 mm, 35.0 mm radial section at 100 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.