51209 bearing
45 × 73 mm · dynamic rating 39 kN · static rating 86.5 kN. Dimensions, load ratings, designation meaning, life estimates and equivalent parts.
51209 specification
| Designation | 51209 |
| Type | Single-direction thrust ball bearing |
| Series | 512 light-medium |
| Bore diameter d | 45 mm |
| Outside diameter D | 73 mm |
| Basic dynamic load rating C | 39 kN (39,000 N) |
| Basic static load rating C0 | 86.5 kN (86,500 N) |
| Ratio C0/C | 2.22 |
| Speed guide, grease lubrication | 5,000 rpm |
| Life exponent p | 3 (ball bearing) |
Values come from the Rotec AI bearing catalogue and are indicative. Confirm against the manufacturer's current catalogue before ordering. Not every dimension (such as width) is listed here.
What the designation 51209 means
| Code | Meaning |
|---|---|
| 512 | Single-direction thrust ball bearing, light-medium series (flat seat washers) |
| 09 | bore code "09" = 9 × 5 = 45 mm |
Basic rating life of the 51209
Basic rating life is L10 = (C / P)p million revolutions, where P is the equivalent dynamic load and p = 3 (ball bearing). For a 51209 with C = 39 kN, the table shows what that gives at different load levels. It is the ISO 281 basic life only: it does not include lubrication, contamination, misalignment or reliability modifiers.
| C / P | P as share of C | L10 (million rev) | L10 at 1,500 rpm | L10 at 3,000 rpm |
|---|---|---|---|---|
| 3 | 33.3% | 27 | 300 | 150 |
| 5 | 20.0% | 125 | 1,400 | 690 |
| 8 | 12.5% | 512 | 5,700 | 2,800 |
| 12 | 8.3% | 1,728 | 19,200 | 9,600 |
For example, a C / P of 5 means the equivalent load is 7.8 kN on this bearing. Use the Load Calculator to work out P for your actual radial and axial loads.
Equivalents of the 51209
Brand-by-brand equivalents for this exact designation are not yet in the Rotec AI cross-reference tables. The Cross-Reference tool accepts SKF, FAG, NSK, NTN, Timken, Koyo and NRB designations, and shows what is catalogued.
Where the 51209 is used
Thrust ball / thrust roller bearings are chosen for: Predominantly axial load. Typical equipment: Vertical pumps, extruders, turbines, marine and heavy gear drives. Thrust roller for higher axial capacity and shock.
Other sizes in the same series
The 51209 is size 8 of 28 in the Rotec AI catalogue for the “512 light-medium” series. The next size down, the 51208, has a bore of 40 mm and a dynamic rating of 44.2 kN. The next size up, the 51210, has a bore of 50 mm and a rating of 49.4 kN (+27%).
Common problems on bearings like the 51209
Most field failures trace back to lubrication, contamination, fits and alignment rather than the bearing itself. These guides explain how to recognise and prevent them:
Questions about the 51209
What are the dimensions of a 51209 bearing?
The 51209 has a bore of 45 mm and an outside diameter of 73 mm. It is a single-direction thrust ball bearing. Series: 512 light-medium.
What is the load rating of a 51209 bearing?
In the Rotec AI catalogue the 51209 has a basic dynamic load rating C of 39 kN and a basic static load rating C0 of 86.5 kN. Always confirm against the manufacturer's current catalogue.
What is the equivalent of a 51209 bearing?
Brand equivalents for the 51209 are not yet in the Rotec AI tables. Use the Cross-Reference tool to check other designations.