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Building A Ball Bearing - Part 3

After examining the manufacturing process for both the inner and outer races as well as the balls, the final part in the Building A Ball Bearing series will delve into the manufacturing process of the cage of the bearings as well as the assembly of all the pieces together to make the final product.

The final stages are the most important to creating a ball bearing which is of the highest precision and quality.

Steel Cages

The steel cages are created from sheet metal which is quite thin, then bent into their final shape in what is called a die. The die is two pieces of steel which are fitted together, when the cage is put into the die and the die is closed, the cage will be bent to the correct shape. The finished product is then removed from the die and is ready to be put together.

Plastic cages are sometimes used as they are cheaper to make and some believe they cause less friction that their steel counterpart. If a plastic cage is made, it will be done by the process of injection moulding, where a mould is filled with melted plastic and allowed to set until hard. The finished plastic cage is then taken out and can be assembled with the other parts of the bearing.

Assembling The Bearing

The bearing will be finally put together now the integral four parts have been made. The inner race is places inside the outer race, pushed as far to one side as possible to allow a space to insert the balls between them.

Dependant on the size, the correct amount of balls will be placed inside, and this will lead to the races being centred and the balls evenly distributed around the bearing evenly. The cage will then be installed to separate the balls from each other. If it is a steel cage, then it will have to be installed and riveted together whilst the plastic cages will usually 'snap' in easily.

Most times, the finished product will then be coated with a formula to prevent rust and then shipped out.

Checking The Quality

Due to the precise nature of the business, vigorous testing will be performed along the way to ensure maximum quality of the finished product. Tests are performed along the way to check for defects along with regular tests during the heat treatment process. Sizes and shape is also of critical importance and the surface of the balls and races must be as smooth as possible.

With the varying types of bearing, there will inevitably be differences in the manufacturing process but this is a great way to learn about the basics!

Other topics in the ACORN Bearing Compendium series include: 

Building a ball bearing - Part 1

Building a ball bearing - Part 2

How are bearings made

Bearing terminology