The Anatomy of a Ball Bearing

Posted Friday, April 10th, 2020 | 802 views

Ball bearings can be made by several materials, but the common bearing is made out of high carbon ferroalloy chromium steel.

The steel comes in the form of a rolled up wire where fixed-length pieces of steel are cut to be used to create the bearing.

Cutting the steal wire

The steel wire is pumped into a high-speed ball bearing machine that cuts the metal into the fixed-size pieces, and before the piece of metal leaves the machine, it is shaped into a ball. This is accomplished when the metal is pushed with extreme force into a round shaped die which makes the spherical shape of the bearing.

At this point you have a “raw ball”. The ball bearing machine can create thousands of raw balls a minute.

After the balls have been pressed and shaped in the die, they are still in rude form and cannot yet be used. These raw balls still have burs on them from being cut and being pressed, and the surface is still uneven. To rectify this the bearings are then put through a flashing machine.

The flashing machine

The flashing machine removes any surface burs and gets them ready for the evening stage. At this stage the bearings do not yet roll straight because they are still uneven.

During these two phases, the balls are kept cool and lubricated with water or oil.

Curing the bearings for strength

After the flashing the bearings need to be heated up to at least 810ºC to strengthen the them and increase durability. Once this is done they are put into oil that is heated to about 60ºC. They are then heated one more time at a temperature of 170ºC.

This heat treatment changes the constitution of the bearings and makes them extremely hard, strong and durable. They then have to go through the precision grinding stage.

Precision grinding stage

Close up bearingsDuring the precision grinding stage, the balls are ground down to make them as spherical as possible and all fixed to the same size. After the precision grinding stage the bearings look sharp, shiny and clean.

The balls are almost 100% spherical and their surface is quite smooth.

The lapping process

At this point the balls are put through a lapping machine to further round them and polish their surface. This is called the lapping process.

Once lapping is complete, the balls are close to 100% spherical, and appear much more shinier than the previous stages.

When a ball bearing is complete, they will act like a mirror and it is at this stage that the manufacturing is complete.

Cleaning the bearings after production

After the bearings are produced, they need to be cleaned of any oil and dirt. This is done by putting them through an ultrasonic machine that exposes the bearings to ultrasonic waves to ensure they are completely clean down to the smallest molecule.

Checking the size of the bearings

At this final stage a sample of the bearings are checked to ensure they are the right size. Bearings come in many sizes but need to be checked for accuracy. They are also checked for any scratches using a special light.

The margin of error has to be less than 0.1 micrometres.

a 16mm diametre bearing should be able to withstand up to 35 tons of weight.

Now you know the anatomy of a ball bearing and exactly how ball bearings are made.


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