Bearings 101: Choosing the Right Bearing for Furniture and Machinery

What a bearing does

A bearing sits between two moving parts - typically a shaft and a housing - and lets them rotate or slide against each other with far less friction than metal-on-metal contact. You'll find bearings inside wheels, castor wheels, and machinery, as well as in furniture parts that rotate or slide, like some drawer mechanisms and swivel fittings.

Ball bearings vs bush (sleeve) bearings

Most replacement bearings fall into one of two broad types. Ball bearings use a ring of small steel balls between an inner and outer race, which is what most people picture when they hear "bearing" - they handle higher speeds and loads with very low friction, which is why they're standard in wheels and castors. Bush bearings (also called sleeve bearings) are a simple solid or split cylinder with no moving balls inside - they're cheaper, simpler, and often perfectly adequate for slower-moving furniture parts like drawer slides or swivel bases, where a full ball bearing would be overkill. If you're not sure which type the part you're replacing uses, a ball bearing will feel like it has slight internal "give" or a faint rolling sensation when you turn it by hand; a bush bearing turns smoothly with no internal play at all.

Why the size matters more than the type

Unlike locks or hinges, where the style is often the main decision, bearings are mostly about exact size and fit. A bearing that's the wrong internal diameter, outer diameter, or width simply won't fit the shaft or housing it's meant to replace - it isn't a matter of preference. Bearing sizes are conventionally written as ID x OD x W (internal diameter by outer diameter by width, in millimetres) - for example, a 20 x 47 x 14 bearing has a 20mm bore, a 47mm outer diameter, and is 14mm wide. Getting even one of these three numbers wrong means the bearing won't seat properly.

What to check before buying

• Internal diameter (bore) - the size of the shaft the bearing sits on
• Outer diameter - the size of the housing it sits inside
• Width - how thick the bearing is
• Sealed or open - many ball bearings are marked with a code ending in 2RS (rubber-sealed on both sides) or ZZ (metal-shielded on both sides), which keeps dust and moisture out; an open bearing with no seal wears out faster in dusty conditions but is easier to clean and re-grease
• Where it's used - furniture, wheels, or machinery, since load and speed requirements differ

Ball bearings are also sometimes sold by a precision grade (ABEC rating), but for furniture, castor wheels, gates, and most day-to-day hardware use, this rating makes little practical difference - it matters far more for high-speed precision equipment than for a drawer slide or a trolley wheel, so it's not worth paying extra for a high ABEC-rated bearing in ordinary household or shop use.

The easiest way to get the right one

Bearings are often stamped with a code on the metal casing itself, which identifies the exact size. If your old bearing has a legible code, bringing it or a clear photo of the stamped numbers is the fastest way to get an exact match. If the code has worn off, measuring the internal diameter, outer diameter, and width - or simply bringing the part it fits into - works just as well.

Related motion hardware

Bearings are often bought alongside other motion hardware:

• [Wheels](/products/wheel) - for sliding gates, windows, and heavy sliding sections
• [Castor wheels](/products/castor-wheel) - swivel wheels fitted under furniture, trolleys, and racks
• [Furniture glides](/categories/wheels-bearings) - for furniture that should slide rather than roll

If a wheel or castor is wobbling, noisy, or seizing, the bearing inside it is often the actual part that needs replacing, rather than the whole wheel assembly.

Common questions

Can I use a sealed bearing where an open one was fitted before?

Generally yes, as long as the ID x OD x W measurements match - a sealed bearing is a straightforward upgrade in dustier or damp conditions, since it keeps grease in and grit out for longer.

Why does my castor wheel feel rough or noisy even though the wheel itself looks fine?

This is almost always the bearing inside the wheel hub, not the wheel surface. Dirt, dried-out grease, or a worn race inside the bearing causes roughness and noise long before the outer wheel shows any visible wear.

Do I need to grease a new bearing before fitting it?

Sealed bearings (2RS or ZZ) come pre-greased and don't need anything added. Open bearings benefit from a light application of the correct grease before fitting, especially in dusty or high-use settings.