Manufaturing - How ball bearings are made
A few centuries ago ball bearings were made of lumps of stone, which were hammered into squares that had rounded edges. Those stones were then put on stone plates with grooves, a wooden plate was put on top as a water wheel and a few days later the friction caused by the water wheel had smoothed those squares into balls.
Today, the ball bearing process has modernised into one that still takes a few days to complete but generates ball bearings that meet the high standards required for today’s machinery.
The Rings In A Ball Bearing
A common ball bearing, known as a Deep Grove Ball Bearing, is made up of steel balls that move inside tracks that have been carved inside of steel rings. The first step in this process is for steel rings to be prepared by machines so that they are the desired thickness. The inner steel ring is inserted into the outer steel ring and both rings are passed through a grinder machine that shapes the rings. Once the two rings are quality checked to ensure that they are the correct size, they are separated and the outer ring goes through a series of machines and grinders that shapes its surfaces to the desired size and shape. A water-based solution is sprayed on the ring as it passes through the grinder so it does not overheat and does not lose its shape. Next, the inner ring goes through a similar process as above to create its precise size.
A lubricated abrasive stone then polishes the rings until they shine so much you can see your reflection in them. They are then washed and coated with thick oil and the raceways in the rings are cleaned with a special solution.
The Balls In A Bearing
The bearing balls actually start out as a steel wire that a machine cuts into pieces. A die punches them into balls with rough edges and these are then ground down. Other machines are then used to round the balls out and give them a mirror finish. Once completed, the balls are put through a furnace that generates high heat so that they harden enough to withstand the pressure put on them.
The Finished Product
Once the rings are reassembled and the balls are ready, the correct number of balls are inserted into the raceways of the rings. The balls are positioned evenly around the raceways, and cages are placed around the ball bearing mechanism to help the balls keep their positions. Once the bearing is successfully tested, the cages around the bearings are sealed together. Next, the ball bearing is immersed in a solvent bath and is quality checked to make sure it operates correctly and quietly. Some bearings are also lubricated with grease and the grease is sealed inside during the manufacturing process.
Finally, the ball bearings are sent through more quality control tests to make sure they are the correct weight before finally being marked with manufacturing information.
Interested in the behind the scenes view? Check out this vignette from Discovery’s Channel’s ‘How It’s Made’