What is Plain Bearing?
A plain bearing is a mechanical part that is charged for bearing loads and allows rotational or sliding moments between two machine parts. It is also called a plain bearing bushing. It is a cylindrical sleeve used to bear loads of light to moderate intensity. Over a shaft, it can slide axially or radially allowing linear or rotary motion between shafts. The main purpose of using plain bearing and sleeve bearing is that the point of support should be free from any wear and tear while the shaft is directly rolled to the machine structure. Plain bearing material is very durable and is composed of only two parts in which the first one is a fixed part where the support is and the second one is in contact with the bush which is the moving part. The support is the main point of load-bearing while the bush part gets worn out due to the frequent motion.
What are its types?
- Sleeve Bearing – This is the most commonly used plain bearing which supports linear shafts, rotating shafts and oscillating shafts and functions through a sliding action.
- Mounted Bearing – It is specially designed according to the specs to get an ideal fit. If there is a loose fit, then creep or slippage can happen in mounted bearings and if there is a very tight fit, then it will affect the free movement of the shaft.
- Spherical Bearings – It allows angular motion between the control arms and linkages. It rotates in two directions to compensate for any misalignment of the shafts.
- Flange Bearings – This bearing supports a shaft running perpendicularly to the mounting surface of the bearing. The flange is also known as the rim of the bearing and is used as the locating medium to hold down the position of the sleeve bearing in its place.
- Thrust Bearings – It is used to prevent any metal to metal contacts in the application of thrust loads. These are very thin and easy to install on a shaft mechanism. It is a self-lubricating type to reduce any extra maintenance expenses.
What are its Advantages and Disadvantages?
The plain bearing design is very basic and it possesses numerous numbers of advantages with a few disadvantages.
- Low cost
- Produces less noise than other bearings
- Simple installation
- High shock resistance, providing better durability
- Allows high rotational speeds
- Plain bearing lubrication not required when using self-lubricating bearings
- High friction during the start-up process
- Requires large axial space
- Friction resisting materials used by plain bearing manufacturers are indispensable
- High wear in comparison with roller bearings
Plain bearing bushing relies on full fluid lubrication which is theoretically capable of working indefinitely. It is used in very critical applications where the failure of bearings can lead to a massive failure of the whole mechanism and can’t be sustained. Generally, it is mostly used in engines and turbomachines like steam turbines of power plants, ship propeller shafts, compressors in pipeline operations and many more types of machinery for aerospace and automobile industries. Plain bearing manufacturers even make bearings for special purposes with different specifications too.