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Building A Ball Bearing - Part 1

The precision when it comes to manufacturing a ball bearing from the start of the process to the end of the process is astounding. For thousands of years, humans have used spherical shapes to make our lives easier. Whether that was logs to help transport objects, to later on the wheel for transportation, the circle shape is one of the most important in our everyday lives today.

This is no exception when it comes to the ball bearing. There are literally thousands of different shapes, sizes and materials to suit the job at hand. But how are these fascinating objects made?

The Parts Of A Bearing

There are four different parts to a ball bearing, there are the cage, inner and outer race and the rolling balls.

The Raw Materials

In the majority of cases, ball bearings are created completely (or the majority) from highly strong and robust steel, this is down to the fact that the bearing will have to take a huge amount of stress in operation. The bearing itself is toughened through a process called heat treating.

How Are They Made?

The rolling ball part of the bearing starts out as a thick steel wire when the wire is cut into smaller pieces and crushed between steel dies, which leaves a ring around the middle of the ball. Most people say this makes the rolling ball look like Saturn.

The races are made in a similar fashion and the process begins with using an appropriate size of steel tubing, machine cutting the basic shape of the races. These will usually be left larger then required, but this is ok as the heat treatment required later on will change the shape slightly but they will be machined back into shape later.

Into The Fire

The races as they are now are then put into a furnace at around 850 degrees Celsius for a varying amount of time depending on the sizes. They will then be oil dipped to cool them down. This also has the added benefit of hardening the races, however, this process also makes them awfully brittle. To avoid this becoming a problem, they are then heated again to around 150 degrees Celsius and cooled in the air rather than in oil. This will solve the problem.

The Grind

The races are now ready to be finished but they must be done with grinding wheels as they are too tough to do by hand. Read on to part two to see how the races are finished as well as how the balls are made, the cage is made, how the parts are put together as well as how the quality of the final product is checked.

Other topics in the ACORN Bearing Compendium series include: 

Building a ball bearing - Part 2

Building a ball bearing - Part 3

How are bearings made

Bearing terminology