About Bearings
Bearings are simple machines found in all those instruments and machines, which roll or tend to roll and are responsible for making the things roll. It is only because of the bearings that electric motors and inline skate wheels spin so smoothly without making much noise. If there were not
bearing in our life then we would be constantly replacing
machines parts and instruments wore out from friction. Bearings have made several things in our life possible.
What is a Bearing?
Bearing is a
mechanical hardware device that allow constrained relative motion between two parts, typically linear or rotational movement. It supports two parts and reduces friction between them. The main objective of bearings is to enable smooth relative movement between two objects or different parts of the same object.
How Bearings Reduce Friction?
Things tend to roll better than slide and that concept works behind bearings. For example wheels in your bike are same as bearings, which facilitate its movement. Just think how much it would be difficult without wheels.
When things slide there is a relative motion between two surfaces involved. Due to the friction between the two surfaces a force tend to slow down the motion and finally stop the motion. But if the two surfaces roll over each other instead of sliding, friction is greatly reduced and the motion becomes smooth. Bearings reduce friction by providing smooth metal balls, and a smooth inner and outer metal surface for the balls to roll against. These balls bear the load and allow the device to spin smoothly.
History of Bearings
There is no definitive evidence but the concept of bearings date as back as construction of the pyramids of Giza. At those times tree trunks were used as linear bearing to laid down under sleds. The concept of ball bearings go all the way back to the Roman Empire as ball bearings were found on the Roman Nemi ships constructed in about 40 A.D. However Leonardo Da Vinci is credited with the first practical designs. In 1791 Philip Vaughn, an English carriage maker and inventor, patented the first axle assembly to use ball bearings. Self-aligning design of the ball bearing is attributed to Sven Wingquist of the SKF ball-bearing manufacturer, when in 1907 he was awarded Swedish patent No. 25406 on its design.
Bearing Materials
Bearings are made of a variety of materials of which the most common and important is stainless steel. Since bearings have to bear a lot of stress, the steel with which it is made needs to be very strong. The quality of steel used determines the durability of the bearing. Cheap bearings are made of hardened carbon-steel or pressed sheet metal, both of which are usually not recommended. The standard industry classification for the steel in some bearings is 52100, which contains 1% chromium and 1% carbon. Such steels can be made very hard and tough by heat treating. 440C stainless steel are used to manufacture bearings which can face rusting threats.
The diversified applications of bearings in different industry and instruments have forced engineers to discover new materials for making bearings that suit specific applications. For example ceramics has become quite popular in making skateboard bearings. Apart from stainless steel other materials used for manufacturing metallic bearings include bronze, nickel, brass, iron, aluminum, copper, etc. Materials used for manufacturing non metallic bearings include ceramics, glass, plastics (e.g., nylon, polyoxymethylene, teflon, UHMWPE, etc.), and even sapphire. Wood was the main material for making bearing in ancient ages.
Types of Bearings
Broad classification of bearings can be done according to the principle of operation and the motions they allow. Different types of bearings are used for different purposes. Some common type of bearings are ball bearings, roller bearings, ball thrust bearings, roller thrust bearings and tapered roller thrust bearings.
Applications of Bearings
Bearings are used in a range of things and instruments that we use in our daily life. They play a very important role in making things move and roll. So their applications range from as small as skating wheels to as large as spacecrafts. Here we have tried to classify the bearings on the basis of their application
| Automotive Bearings |
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Aircraft Bearings |
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Instrument Bearings |
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Marine Bearings |
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Slewing Bearings |
| Machine Tool Bearings |
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Clutch Release Bearings |
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Electric Motor Bearings |
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Engine Bearings |
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Innovative Application of Ball Bearings
One very interesting, innovative and highly useful application of ball bearings has come to be seen in the new San Francisco International Airport. There are 267 columns used to bear the entire weight of the airport. Each column is placed on a ball bearing of a diameter of 5 feet made of stainless steel. Each ball rests in a concave base that is connected to the ground. In case of an earthquake, the ground can move up to 20 inches in either direction. The columns resting on the balls move lesser than this as they roll around in their bases, which helps isolate the building from the motion of the ground. After the earthquake is over, the columns are recenterd to their bases due to gravity.
Caring of Bearings
The most significant rule of using bearings is "Keep Bearings Clean". The presence of minute particles as small as 0.005mm in the ball bearings can create problems and affect the performance of the bearing. Therefore avoid using the bearings in the environments where particles may be present.
Once the particles get inside bearings, they can cause scratches and abrasions and shortened their life. The particles are also responsible for creating acoustic noise and vibrations. Despite using shields and seals to check the entry of particles, they enter from the gap between the shield and inner ring of shields.
Tips to Prevent Bearings from Contamination
- Try to keep the bearing handling area as well as bearing accessories as clean as you can.
- Remove the bearing packaging just before its use.
- Before moving the bearing to a container make sure that it is clean. Lid of the container should always be closed and should be cleaned regularly to prevent particles gathering.
- Do not use bearings which have been ever dropped. Using such bearings can cause high level of acoustic noise.
- Prior to applying adhesives to bearings, it should be cleaned with a cloth using an alcoholic agent to remove oily materials like anti-corrosion oil from the rings.
- Before applying lubricant to the outer circumference of bearings make sure that it is not contaminated.
Bearings Associations
Below is listed some of the very important associations working in the area of bearing industry. Know more about other
hardware industry associations and
mechanical contractors association.
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