Plain bearings, also known as bushings or sleeve bearings, are a type of bearing that use a sliding surface, such as metal or plastic, to support a rotating or sliding shaft. They are commonly used in applications where low cost and simple design are more important than high precision or speed.

Plain bearings work by providing a sliding surface between the shaft and the bearing, which reduces friction and allows for smooth rotation or sliding. The sliding surface can be made of a variety of materials, including bronze, plastic, or even wood, depending on the specific application requirements.

One advantage of plain bearings is that they are simple and inexpensive to manufacture and maintain. They are also able to handle heavy loads and are resistant to shock and vibration. However, they are typically not suitable for high-speed or high-precision applications, as the sliding friction can cause wear and reduce accuracy.

Overall, plain bearings are a reliable and cost-effective type of bearing that are widely used in a variety of applications, including automotive, construction, and industrial machinery. They are especially well-suited for applications that require high load capacity and durability, but do not require high precision or speed.