A Plain Bearing is the simplest bearing – just two smooth surfaces sliding against each other. We use metal or plastic sleeves so a shaft can pivot without rollers. They handle moderate loads and fit tight spaces. We add grease or soak them in oil so parts don’t grind. When they wear, the machine gets noisy and sloppy. We replace the bushing sleeve and add fresh grease. No fancy parts, but they get the job done where space and cost matter.