What are oilless bearings, and how do they work?
Oil-less bearing may refer to is a ball bearing that does not require oil for it's lubrication because a lubricant such as powdered graphite or grease is already incorporated in the bearing housing and hermetically sealed - meaning that it is lubricated for it's lifetime. These are maintenance free and are ideally suitable for use in difficult working environment, high temperature application, etc. Furthermore, the sealing prevents ingress of contaminant to the bearing housing.
Oil-less bearings may also refer to Bush Bearings or simply “bushings” that does not require periodic lubrication - because a lubricant such as powdered graphite is incorporated in the material of which the bearing is made. These are also known as Graphite Embedded Bearings and have 20-25% Graphite inserts on the walls/surface that provide lubrication at all times also brings down the co-efficient of friction.
Bush bearings are used primarily in machinery that has a rotating or a sliding shaft component. Also called sleeve bearings or journal bearings, these bushes have no rolling elements. Some are made of a relatively soft metal, such as bronze, to protect the shaft journals. The example that comes to my mind is the CRANKSHAFT of an automobile engine. Most hand operated drilling and grinding machines, water pumps and motors use bush bearings on the shafts.