Single-direction thrust ball bearings are designed to carry axial load in one direction. The table below lists selected SKF standard 51100-series dimensions, basic axial load ratings and speed ratings. It covers the plain standard designations shown only; it is a catalog lookup to identify and compare bearings, not a calculation of the load a bearing can safely carry in a particular machine.

SKF 51100-series thrust bearing ratings

Choose the bearing designation and confirm its bore, outside diameter and height against the available space. The dynamic rating C and static rating C0 are different reference values used in bearing calculations. The reference speed and limiting speed also have different meanings and depend on operating conditions.

Dynamic and static load ratings

A basic dynamic load rating is used in rolling-bearing life calculations for a bearing that rotates under load. It is not an allowable load for every service life, reliability, lubrication state or contamination level. The required rating depends on the equivalent bearing load, speed, required life and applicable adjustment factors. For ball bearings, a basic rating-life relationship is often written using the ratio C/P raised to the third power, where P is the equivalent dynamic load, but that equation is only one part of a bearing selection calculation.

The static rating C0 applies to a non-rotating or slowly oscillating bearing under static load. Static selection also considers the equivalent static bearing load and an application-specific static safety factor. Compare C and C0 only with the corresponding calculated loads and method; they are not directly interchangeable with each other or with a manufacturer’s suggested operating load.

Check the application direction and speed

SKF describes single-direction thrust ball bearings as supporting axial load in one direction and warns against radial load. If the machine can load the bearing in both axial directions, a second bearing or a different arrangement may be needed. Misalignment, washer support, seat flatness, lubrication, heat, contamination and preload can all change bearing behavior. Confirm the exact arrangement and mounting details with the current product catalog.

The reference speed is a calculation-based thermal reference under assumed operating conditions. The limiting speed is a separate boundary value for the product. Neither value guarantees suitability at a particular temperature or lubrication method. Read SKF’s notes about lubrication, load, cage, and mounting and use the lower application limit where the actual arrangement requires it.

Practical selection example

Imagine a compact mechanism with an axial reaction and a 15 mm shaft seat. The table can help identify a 51102 candidate and its basic envelope, then show the corresponding C, C0 and speed ratings. The next step is not to divide a maximum force by C0 and assume the result is safe. Calculate the bearing load from the actual shaft and housing arrangement, account for other loads and duty cycles, and determine life and static safety factor using the current SKF method or another applicable design standard.

This distinction prevents a common mistake: reading a catalog capacity as a permissible service load. The listed ratings support a selection calculation; they do not include your mounting stiffness, reliability target, temperature, vibration, lubrication interval or contamination control. Verify the exact product suffix, current availability and datasheet before purchasing or releasing a drawing.

Also compare the required shaft seat and housing shoulder dimensions with the bearing washer geometry and abutment requirements. A bearing with a matching bore can still be wrong if the housing cannot support the washer face or if the assembly permits unintended radial load. Check the catalog drawings, minimum-load factor, lubrication and bearing arrangement before finalizing the part. The size table is useful at the screening stage; detailed selection still depends on the actual machine and load history.

Related engineering references

Browse more mechanical design topics in the Mechanitec Engineering category.

Sources

• SKF single-direction thrust ball bearing catalog, series table and selection details.
• SKF 51216 product information, direction of load and rating terminology.