Each one should have a grease zerk. The picture someone posted with the bandsaw shows a grease zerk on it.
you pump 10-12 pumps of grease into each bearing every 2 hours of use or so.
Failure to do so, or trying to pack once a season, will wear them out quickly.
These are just simple sleeves, metal on metal. There is no fancy bearing, you are looking at the bearing - the shiny metal, it rubs on the other part.
It needs tons of grease to flush out dirt, and to allow a buildup, a film, of fresh grease to be spinning around in there on those grooves.
It needs grease, grease, grease.
Often. Dad would go through a gunfull or 2 in a single day when he was running the old IHC disk. Grease was one of those staples, like sugar and flour and such. You just use a whole lot of grease.
There is nothing to protect those housings from the shafts other than a constant film of grease. This is not a high-tech thing, it is 1900's technology. Build it out of metal, and grease it often and lots to keep it a film of fresh grease between the metal parts.
Some old style had wood blocks in there instead of the metal outer grooves, the steel shaft would turn on the hardwood blocks.
Yours are metal on metal.
Some have softer inserts, made of a babbit material, and you could replace the babbits. In the outer parts, I'm not sure if that is all one piece, or if it has a bit of a liner in it? They were made both ways. If it has the thin liner, then that different type of metal was the 'bearing' that you could replace.
Many were just iron on iron, grease a lot or you wear it out.
It is difficult to find those outer hubs any more, I believe? Wear it out and you junk the disk.
Grease, grease, grease..... It is desiogned to just flow out and take the dirt with it....