Oil wicking

Felt holds many times its own weight in oil and gives it back slowly. That is the whole mechanism behind a felt wick, and it is why the oldest machines in a mill are often the ones still running.

The locked fibre structure behaves like a sponge with very fine passages through it. Capillary action pulls oil in and holds it there against gravity, so a wick stays charged instead of draining to the bottom of the housing.

Pressed against a moving shaft, the wick gives up only what the contact takes away. The feed matches the demand on its own, with no drip rate to set and nothing to block, and one charge can keep a bearing fed for months.

It filters while it feeds. Grit suspended in the oil is caught in the fibre rather than carried onto the bearing surface, which is often the real reason a wicked bearing outlasts a pressure-fed one on dirty work.