Understanding the load a bearing will experience is the starting point for any selection. Loads are generally classified as:

• Radial loads – acting perpendicular to the shaft
• Axial (thrust) loads – acting parallel to the shaft
• Combined loads – a mix of radial and axial forces

The magnitude of the load, along with whether it's constant, fluctuating, or subject to shock loading, will influence which bearing type and size is appropriate.

Bearings are rated for maximum operating speeds, which vary depending on design, size, cage material, and lubrication method. High-speed applications typically favour ball bearings, while heavier, lower-speed applications may be better suited to roller bearings.

The environment a bearing will operate in has a major impact on its performance and lifespan. Consider factors such as:

• Temperature range – extreme heat or cold can affect lubrication and material properties
• Contamination risk – dust, dirt, and debris can accelerate wear if sealing is inadequate
• Moisture and washdown exposure – may call for corrosion-resistant materials or stainless steel/thermoplastic housings
• Chemical exposure – certain environments require specialist seals or coatings

Shaft and housing alignment isn't always perfect, particularly in larger or older installations. If some misalignment is likely, self-aligning ball bearings, spherical roller bearings, or housed units with a spherical outer race can accommodate this without compromising performance.

Consider how and where the bearing will be installed. Standalone bearings require a precision-bored housing and careful alignment during fitting, while housed bearing units (such as pillow block, flanged, or take-up units) are pre-engineered for straightforward bolt-on installation, which can significantly reduce installation time.

The right sealing arrangement helps protect against contamination and retain lubrication. Options range from shielded and sealed bearings to units with integrated seals, and the choice will depend on the operating environment and how frequently maintenance can be carried out. Lubrication method, grease or oil, should also be considered based on speed, temperature, and maintenance access.

The available physical space, including shaft diameter and surrounding clearance, will narrow down the range of suitable bearing types and sizes. Compact designs such as needle roller bearings or miniature ball bearings may be necessary where space is limited.

Consider how easily the bearing can be inspected, maintained, or replaced once installed. In hard-to-reach locations, a bearing with a longer expected service life or reduced lubrication requirements can help minimise the need for frequent maintenance.

While upfront cost is a factor, it's worth weighing this against the total cost of ownership, including installation time, maintenance requirements, and expected service life. A higher-quality bearing suited to the application can often reduce costs over time by minimising downtime and replacement frequency.