Dust Is An Abrasive Wherever Two Parts Move

Dust looks like a cosmetic problem and behaves like a mechanical one. Once it reaches a moving joint it becomes a grinding compound working continuously against surfaces that were meant to slide cleanly.

What dust actually is

Household dust is a mixture of fibres, skin, and a substantial mineral fraction of sand and mineral particles tracked in from outside.

The mineral part is harder than most plastics and many soft metals, which is exactly the condition required for one surface to cut another.

Fibres are relatively harmless in a bearing but excellent at blocking airflow, so the two fractions of the same dust cause two different failures.

Grit becomes a lapping compound

A sliding surface with hard particles trapped between the faces behaves like a workshop lapping operation. Material is removed slowly and evenly, and the clearance grows.

Once clearance grows the joint develops play, and play lets the parts strike each other rather than glide, which removes material faster still.

This is why an old mechanism feels loose rather than stiff. The wear pattern is subtractive, and nothing puts the material back.

Lubricant holds the grit in place

Oil and grease attract dust and then hold it exactly where it does most damage. A greased rail in a dusty room collects a dark paste within weeks.

That paste is more abrasive than clean grit alone, because the lubricant keeps the particles pressed against the surface instead of letting them fall away.

Sealed or dry lubrication exists largely for this reason, trading some efficiency for the ability to run in an environment that is not clean.

Airflow paths concentrate the load

Anything with a fan pulls the room's dust through itself. The dust does not distribute evenly but collects at the first restriction it meets.

Fins, filters and grilles accumulate a mat that reduces airflow, and reduced airflow raises temperature everywhere downstream of the blockage.

The fan itself gathers deposits on its blades, which unbalances it, and an unbalanced fan wears its own bearings at an accelerating rate.

Cleaning method decides whether it helps

Blowing dust off a mechanism drives some of it further in, past seals that were doing their job until the moment of the cleaning.

Removing dust with suction or a damp cloth takes it away from the machine instead of relocating it into somewhere harder to reach.

The useful habit is to clean the entry points rather than the visible surfaces, since the visible dust was never the part causing wear.