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.

What is the function of the bushing?

In the moving parts, the wear of the parts is caused by long-term friction. When the gap between the shaft and the holes is worn to a certain extent, the parts must be replaced, so the designer selects the hardness and wear resistance at the time of design. The better material is the bushing or bushing, so that the automatic bushing can reduce the wear of the shaft and the seat. When the bushing or bushing is worn to a certain extent for replacement, the cost of replacing the shaft or the seat can be saved. It is said that the bushing and the seat adopt an interference fit, and the shaft has a clearance fit, because no matter how the side piece is, it can not avoid the wear and tear, and can only prolong the life, and the shaft type parts are relatively easy to process; there are some new ones. The designers do not like this design, think that this is to increase the cost when manufacturing, but after a period of use, the repair should still be modified according to this method, but the transformation is easy to cause the accuracy of the equipment to reduce, the reason is very simple, the second Machining is not able to guarantee the position of the center of the seat.